     [file docstyle.texi not included]
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tramp trampver User Manual
**************************

This file documents tramp trampver, a remote file editing package for Emacs.

tramp stands for ``Transparent Remote (file) Access, Multiple Protocol''.  This package provides an easy, convenient, and consistent interface to editing remote files transparently, just as if they are local files.  This extends to editing, version control, dired, and more.

You can find the latest version of this document on the web at trampurl.

There is a mailing list for tramp, available at tramp-bug-report-address, and archived at the tramp Mail Archive (https://lists.gnu.org/r/tramp-devel/).

Copyright © 1999--2025 Free Software Foundation, Inc.

     Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being ``A GNU Manual'', and with the Back-Cover Texts as in (a) below.  A copy of the license is included in the section entitled ``GNU Free Documentation License''.

     (a) The FSF's Back-Cover Text is: ``You have the freedom to copy and modify this GNU manual.''

An overview of tramp
********************

tramp is for transparently accessing remote files from within Emacs.  tramp enables an easy, convenient, and consistent interface to remote files as if they are local files.  tramp's transparency extends to editing, version control, and dired.

tramp can access remote hosts using any number of access methods, such as ssh, scp, telnet, and related programs.  If these programs can successfully pass ASCII characters, tramp can use them.  tramp does not require or mandate 8-bit clean connections.

tramp's most common access method is through ssh, a more secure alternative to ftp and other older access methods.

tramp on MS Windows operating systems is integrated with the PuTTY package, and uses the plink program.

tramp mostly operates transparently in the background using the connection programs.  As long as these programs enable remote login and can use the terminal, tramp can adapt them for seamless and transparent access.

tramp temporarily transfers a remote file's contents to the local host editing and related operations.  tramp can also transfer files between hosts using standard Emacs interfaces, a benefit of direct integration of tramp in Emacs.

tramp can transfer files using any number of available host programs for remote files, such as rcp, scp, rsync or (under MS Windows) pscp.  tramp provides easy ways to specify these programs and customize them to specific files, hosts, or access methods.

For faster small-size file transfers, tramp supports encoded transfers directly through the shell using mimencode or uuencode provided such tools are available on the remote host.

tramp behind the scenes
.......................

Accessing a remote file through tramp entails a series of actions, many of which are transparent to the user.  Yet some actions may require user response (such as entering passwords or completing file names).  One typical scenario, opening a file on a remote host, is presented here to illustrate the steps involved:

C-x C-f to initiate find-file, enter part of the tramp file name, then hit TAB for completion.  If this is the first time connecting to that host, here's what happens:

  * tramp invokes telnet HOST or ssh -l
     USER HOST and establishes an external process to connect to the remote host.  tramp communicates with the process through an Emacs buffer, which also shows output from the remote host.

  * The remote host may prompt for a login name (for telnet, for example) in the buffer.  If on the other hand, the login name was included in the file name portion, tramp sends the login name followed by a newline.

  * The remote host may then prompt for a password or passphrase (for ssh or for telnet).  tramp displays the password prompt in the minibuffer.  tramp then sends whatever is entered to the remote host, followed by a newline.

  * tramp now waits for either the shell prompt or a failed login message.

     If tramp does not receive any messages within a timeout period (a minute, for example), then tramp responds with an error message about not finding the remote shell prompt.  If there are any messages from the remote host, tramp displays them in the buffer.

     For any login failed message from the remote host, tramp aborts the login attempt, and repeats the login steps.

  * Upon successful login, if tramp recognizes the shell prompt from the remote host, tramp prepares the shell environment by turning off echoing, setting the shell prompt, and other housekeeping chores.

     Note that for the remote shell, tramp invokes /bin/sh.  The remote host must recognize exec /bin/sh and execute the appropriate shell.  This shell must support Bourne shell syntax.

  * tramp executes cd and ls commands to find which files exist on the remote host.  tramp sometimes uses echo with globbing.  tramp checks if a file or directory is writable with test.  After each command, tramp parses the output from the remote host for completing the next operation.

  * After remote file name completion, tramp transfers the file contents from the remote host.

     For inline transfers, tramp sends a command, such as mimencode -b /path/to/remote/file, waits until the output has accumulated in the buffer, then decodes that output to produce the file's contents.

     For external transfers, tramp sends a command as follows:

          $ scp user@host:/path/to/remote/file <TMP>/tramp.4711

     tramp reads the local temporary file <TMP>/tramp.4711 into a buffer, and then deletes the temporary file. (Temporary directory)

  * Edit, modify, change the buffer contents as normal, and then save the buffer with C-x C-s.

  * tramp transfers the buffer contents to the remote host in a reverse of the process using the appropriate inline or external program.

I hope this has provided you with a basic overview of what happens behind the scenes when you open a file with tramp.

Obtaining tramp
***************

tramp is included as part of Emacs.

tramp is also freely packaged for download on the Internet at https://ftp.gnu.org/gnu/tramp/.  The version number of tramp can be obtained by the variable tramp-version. For released tramp versions, this is a three-number string like ``2.4.5''.

A tramp release, which is packaged with Emacs, could differ slightly from the corresponding standalone release.  This is because it isn't always possible to synchronize release dates between Emacs and tramp.  Such version numbers have the Emacs version number as suffix, like ``2.4.5.27.2''.  This means tramp 2.4.5 as integrated in Emacs 27.2.  A complete list of tramp versions packaged with Emacs can be retrieved by

     (assoc 'Tramp customize-package-emacs-version-alist)

tramp is also available as GNU ELPA (https://elpa.gnu.org) package.  Besides the standalone releases, further minor versions of tramp will appear on GNU ELPA, until the next tramp release appears.  These minor versions have a four-number string, like ``2.4.5.1''.  The manual of the latest tramp ELPA package is located at https://elpa.gnu.org/packages/doc/tramp.html.

tramp development versions are available on Git servers. Development versions contain new and incomplete features.  The development version of tramp is always the version number of the next release, plus the suffix ``-pre'', like ``2.4.4-pre''.

One way to obtain tramp from the Git server is to visit the Savannah project page at the following URL and then clicking on the Git link in the navigation bar at the top.

https://savannah.gnu.org/projects/tramp/

Another way is to follow the terminal session below:

     $ cd ~/emacs
     $ git clone https://git.savannah.gnu.org/git/tramp.git

From behind a proxy:

     $ git config --global http.proxy https://user:pwd@proxy.server.com:8080
     $ git clone https://git.savannah.gnu.org/r/tramp.git

tramp developers:

     $ git clone login@git.sv.gnu.org:/srv/git/tramp.git

After one of the above commands, ~/emacs/tramp will containing the latest version of tramp.

To fetch updates from the repository, use git pull:

     $ cd ~/emacs/tramp
     $ git pull

Run autoconf as follows to generate an up-to-date configure script:

     $ cd ~/emacs/tramp
     $ autoconf

See the file INSTALL in that directory for further information on how to install tramp.

Short introduction how to use tramp
***********************************

tramp extends the Emacs file name syntax by adding a remote component.  A remote file name always looks like method,user@host,/path/to/file.

You can use remote files exactly like ordinary files, that means you can open a file or directory by C-x C-f method,user@host,/path/to/file RET, edit the file, and save it.  You can also mix local files and remote files in file operations with two arguments, like copy-file or rename-file.  And finally, you can even run processes on a remote host, when the buffer you call the process from has a remote default-directory.

File name syntax
================

Remote file names have method, user and host parts prepended.  All of them, and also the local file name part, are optional, in case of a missing part a default value is assumed.  The default value for an empty local file name part is the remote user's home directory.  The shortest remote file name is thus -,,.  The - notation for the default method is used for syntactical reasons, see Default Method.

The method part describes the connection method used to reach the remote host, see below.

The user part is the user name for accessing the remote host. For the smb method, this could also require a domain name, in which case it is written as user%domain.

The host part must be a host name which can be resolved on your local host.  It could be a short host name, a fully qualified domain name, an IPv4 or IPv6 address, see File name syntax.  Some connection methods also support a notation for the port to be used, in which case it is written as host#port.

Using ssh and plink
===================

If your local host runs an SSH client, and the remote host runs an SSH server, the simplest remote file name is ssh,user@host,/path/to/file.  The remote file name ssh,, opens a remote connection to yourself on the local host, and is often used for testing tramp.

On MS Windows, PuTTY is often used as the SSH client.  Its plink method can be used there to open a connection to a remote host running an ssh server: plink,user@host,/path/to/file.

Using su, sudo, doas, run0, androidsu and sg
============================================

Sometimes, it is necessary to work on your local host under different permissions.  For this, you can use the su or sudo connection method.  If your system is systemd-based, there is the run0 connection method.  On OpenBSD systems, the doas connection method offers the same functionality.  If your local system is Android, use the method androidsu instead of su.

These methods use root as default user name and the return value of (system-name) as default host name.  Therefore, it is convenient to open a file as sudo,,/path/to/file.

The method sg stands for ``switch group''; here the user name is used as the group to change to.  The default host name is the same.

Combining ssh or plink with su, sudo, doas or run0
==================================================

If the su, sudo, doas or run0 method should be performed on another host, it can be combined with a leading ssh or plink method.  That means that tramp connects first to the other host with non-administrative credentials, and changes to administrative credentials on that host afterwards.  In a simple case, the syntax looks like sshpostfixhopuser@host|sudo,,/path/to/file. See Ad-hoc multi-hops.

Using sudoedit
==============

The sudoedit method is similar to the sudo method. However, it is a different implementation: it does not keep an open session running in the background.  This is for security reasons; on the backside this method has worse performance than the sudo method, it is restricted to localhost only, and it does not support external processes.

Using smbclient
===============

In order to access a remote MS Windows host or Samba server, the smbclient client is used.  The remote file name syntax is smb,user%domain@host,/path/to/file.  The first part of the local file name is the share exported by the remote host, path in this example.

Using GVFS-based methods
========================

On systems which have GVFS (the GNOME Virtual File System) installed, its offered methods can be used by tramp. Examples are sftp,user@host,/path/to/file, afp,user@host,/path/to/file (accessing Apple's AFP file system), dav,user@host,/path/to/file, davs,user@host,/path/to/file (for WebDAV shares) and mtp,device,/path/to/file (for media devices).

Using GNOME Online Accounts based methods
=========================================

GVFS-based methods also include GNOME Online Accounts, which support the Files service.  These are the Google Drive file system, and the OwnCloud/NextCloud file system.  The file name syntax here is always gdrive,john.doe@gmail.com,/path/to/file (john.doe@gmail.com stands here for your Google Drive account), or nextcloud,user@host#8081,/path/to/file (8081 stands for the port number) for OwnCloud/NextCloud files.

Using FUSE-based methods
========================

FUSE (Filesystem in Userspace) allows users to mount a virtual file system.  It is also used by GVFS internally, but here we discuss methods which do not use the GVFS API.

A convenient way to access system storages is the rclone program.  If you have configured a storage in rclone under a name storage (for example), you can access it via the remote file name syntax rclone,storage,/path/to/file.  User names are not needed.

On local hosts which have installed the sshfs client for mounting a file system based on sftp, this method can be used.  All remote files are available via the local mount point. tramp aids in mounting the file system if it isn't mounted yet, and it supports the access with the usual file name syntax sshfs,user@host,/path/to/file.

Using Android
=============

An Android device, which is connected via USB to your local host, can be accessed via the adb command.  No user or host name is needed.  The file name syntax is adb,,/path/to/file.

Configuring tramp
*****************

tramp is initially configured to use the scp program to connect to the remote host.  Just type C-x C-f and then enter file name scp,user@host,/path/to/file.  For details, see Default Method, see Default User, see Default Host.

For problems related to the behavior of the remote shell, see Remote shell setup.

For changing the connection type and file access method from the defaults to one of several other options, see Connection types.

Note that some user options described in these examples are not auto loaded by Emacs.  All examples require tramp to be installed and loaded:

     (customize-set-variable 'tramp-verbose 6 "Enable remote command traces")

For functions used to configure tramp, the following clause may be used in your init file:

     (with-eval-after-load 'tramp (tramp-change-syntax 'simplified))

Changing other variables via directory-local variables on a remote directory must be enabled by setting enable-remote-dir-locals to non-nil, see Directory Variables (emacs).

Optional methods which must be enabled first
============================================

Not all methods are enabled by default after loading tramp. Some of them don't work on the local host.  Some of them are optional, and must be enabled if it is intended to use them.  For all methods described in this manual, it is indicated when the method is optional.

 -- Command: tramp-enable-method method
     This command enables the optional method METHOD, a string.  The command can be invoked interactively like M-x tramp-enable-method RET toolbox RET, with toolbox being an optional method.

If you want to enable an optional method permanently, add something like this to your .emacs file:

     (with-eval-after-load 'tramp (tramp-enable-method "toolbox"))

Types of connections to remote hosts
====================================

Inline method and external method are the two basic types of access methods.  While they both use the same remote shell access programs, such as rsh, ssh, or telnet, they differ in the file access methods.  Choosing the right method becomes important for editing files, transferring large files, or operating on a large number of files.

The performance of the external methods is generally better than that of the inline methods, at least for large files.  This is caused by the need to encode and decode the data when transferring inline.

The one exception to this rule are the scp-based access methods.  While these methods do see better performance when actually transferring files, the overhead of the cryptographic negotiation at startup may drown out the improvement in file transfer times.

External methods should be configured in such a way that they don't require a password (with ssh-agent, or similar).  Modern scp implementations offer options to reuse existing ssh connections, which tramp enables by default if available.  If that is not possible, you should consider Password handling, otherwise you will be prompted for a password for every copy action.

Inline methods
==============

Inline methods use the same login connection to transfer file contents.  Inline methods are quick and easy for small files.  They depend on the availability of suitable encoding and decoding programs on the remote host.  For local source and destination, tramp may use built-in equivalents of such programs in Emacs.

Inline methods can work in situations where an external transfer program is unavailable.  Inline methods also work when transferring files between different user identities on the same host.

tramp checks the remote host for the availability and usability of one of the commands defined in tramp-remote-coding-commands.  tramp uses the first reliable command it finds.  tramp's search path can be customized, see Remote programs.

In case none of the commands are available, tramp first transfers a small Perl program to the remote host, and then tries to use that program for encoding and decoding.

To increase transfer speeds for large text files, tramp can use compression before encoding.  The user option tramp-inline-compress-start-size specifies the file size above which to use this optimization.  This feature depends on the availability and usability of one of the commands defined in tramp-inline-compress-commands.

rsh

     rsh is an option for connecting to hosts within local networks since rsh is not as secure as other methods. There should be no reason to use it, as ssh is a both a complete replacement and ubiquitous.

ssh

     ssh is a more secure option than others to connect to a remote host.

     ssh can also take extra parameters as port numbers.  For example, a host on port 42 is specified as host#42 (the real host name, a hash sign, then a port number).  It is the same as passing -p 42 to the ssh command.

telnet

     Connecting to a remote host with telnet is as insecure as the rsh method.

su

     Instead of connecting to a remote host, su program allows editing as another user.  The host can be either localhost or the host returned by the function (system-name).  See Multi-hops for an exception to this behavior.

androidsu

     Because the default implementation of the su method and other shell-based methods conflict with non-standard su implementations popular among Android users and the restricted command-line utilities distributed with that system, a largely equivalent androidsu method is provided for that system with workarounds for its many idiosyncrasies, with the exception that multi-hops are unsupported.

     This is an optional method, see Optional methods.  It is enabled by default on android systems only.

sudo

     Similar to su method, sudo uses sudo. sudo must have sufficient rights to start a shell.

     For security reasons, a sudo connection is disabled after a predefined timeout (5 minutes by default).  This can be changed, see Predefined connection information.

doas

     This method is used on OpenBSD like the sudo command.  Like the sudo method, a doas connection is disabled after a predefined timeout.

run0

     This method is used on systemd-based hosts.  A run0 connection is disabled after a predefined timeout as well.

     This is an optional method, see Optional methods.

sg

     The sg program allows editing as different group.  The host can be either localhost or the host returned by the function (system-name).  The user name must be specified, but it denotes a group name.  See Multi-hops for an exception to this behavior.

sshx

     Works like ssh but without the extra authentication prompts. sshx uses ssh -t -t -l USER -o RemoteCommand='/bin/sh -i' HOST to open a connection with a ``standard'' login shell.  It supports changing the remote login shell /bin/sh.

     Note that sshx does not bypass authentication questions.  For example, if the host key of the remote host is not known, sshx will still ask ``Are you sure you want to continue connecting?''.  tramp cannot handle such questions. Connections will have to be setup where logins can proceed without such questions.

     sshx is useful for MS Windows users when ssh triggers an error about allocating a pseudo tty.  This happens due to missing shell prompts that confuses tramp.

     sshx supports the -p argument.

krlogin

     This method is also similar to ssh.  It uses the krlogin -x command only for remote host login.

     This method is an optional method, see Optional methods.

ksu

     This is another method from the Kerberos suite.  It behaves like su.  It is an optional method, see Optional methods.

plink

     plink method is for MS Windows users with the PuTTY implementation of SSH.  It uses plink -ssh to log in to the remote host.  It supports changing the remote login shell /bin/sh.

     Check the Share SSH connections if possible control for that session.

     plink method supports the -P argument.

plinkx

     Another method using PuTTY on MS Windows with session names instead of host names.  plinkx calls plink -load SESSION -t.  User names and port numbers must be defined in the session.  It supports changing the remote login shell /bin/sh.

     Check the Share SSH connections if possible control for that session.

The following methods allow to access running containers in different ways:

docker

     Integration for Docker containers.  The host name may be either a running container's name or ID, as returned by docker ps.

podman

     Podman is an alternative to docker which may be run rootless, if desired.

kubernetes

     Integration for containers in Kubernetes pods.  The host name is POD, or CONTAINER.POD if an explicit container name shall be used.  Otherwise, the first container in a pod is used.

     This method does not support user names.

toolbox

distrobox

     Integration of Toolbox or Distrobox system containers, respectively. The host name may be either a container's name or ID, as returned by toolbox list -c or distrobox list.  Without a host name, the default Toolbox container for the host will be used.  There is no such default for Distrobox.

     Contrary to the other container-based methods, these two methods start a created container, if it isn't running yet.

     These are optional methods, see Optional methods.  They do not support user names.

flatpak

     Integration of Flatpak sandboxes.  The host name may be either an application ID, a sandbox instance ID, or a PID, as returned by flatpak ps.

     This is an optional method, see Optional methods.  It does not support user names.

apptainer

     Integration of Apptainer instances.  The host name is the instance name, as returned by apptainer instance list.

     This is an optional method, see Optional methods.  It does not support user names.

nspawn

     Integration of systemd-nspawn instances.  The host name is the instance name, as returned by machinectl list --all.

     This is an optional method, see Optional methods.

External methods
================

External methods operate over multiple channels, using the remote shell connection for some actions while delegating file transfers to an external transfer program.

External methods save on the overhead of encoding and decoding of inline methods.

Since external methods have the overhead of opening a new channel, files smaller than tramp-copy-size-limit still use inline methods.

rcp

     This method uses the rsh and rcp commands to connect to the remote host and transfer files.  This is the fastest access method available.

     The alternative method remcp uses the remsh and rcp commands.

scp

     Using a combination of ssh to connect and scp to transfer is the most secure.  While the performance is good, it is slower than the inline methods for smaller files.  Though there is no overhead of encoding and decoding of the inline methods, scp's cryptographic handshake negates those speed gains.

     ssh-based methods support -p feature for specifying port numbers.  For example, host#42 passes -p 42 in the argument list to ssh, and -P 42 in the argument list to scp.

rsync

     ssh command to connect in combination with rsync command to transfer is similar to the scp method.

     rsync performs much better than scp when transferring files that exist on both hosts.  However, this advantage is lost if the file exists only on one side of the connection, during the first file transfer.

     This method supports the -p argument.

scpx

     scpx is useful to avoid login shell questions.  It is similar in performance to scp.  scpx uses ssh -t -t -l USER -o RemoteCommand='/bin/sh -i' HOST to open a connection.  It supports changing the remote login shell /bin/sh.

     scpx is useful for MS Windows users when ssh triggers an error about allocating a pseudo tty.  This happens due to missing shell prompts that confuses tramp.

     This method supports the -p argument.

pscp

psftp

     These methods are similar to scp or sftp, but they use the plink command to connect to the remote host, and they use pscp or psftp for transferring the files. These programs are part of PuTTY, an SSH implementation for MS Windows.

     They support changing the remote login shell /bin/sh.

     Check the Share SSH connections if possible control for that session.

     These methods support the -P argument.

dockercp

podmancp

     These methods are similar to docker or podman, but they use the command docker cp or podman cp for transferring large files.

     These copy commands do not support file globs, and they ignore a user name.

fcp

     This method is similar to scp, but uses fsh to connect and fcp to transfer files.  fsh/fcp, a front-end for ssh, reuse ssh session by submitting several commands.  This avoids the startup overhead due to scp's secure connection.  Inline methods have similar benefits.

     The command used for this connection is: fsh HOST -l USER /bin/sh -i

     fsh has no inline method since the multiplexing it offers is not useful for tramp.  fsh connects to remote host and tramp keeps that one connection open.

     This is an optional method, see Optional methods.

nc

     Using telnet to connect and nc to transfer files is sometimes the only combination suitable for accessing routers or NAS hosts.  These dumb devices have severely restricted local shells, such as the busybox and do not host any other encode or decode programs.

     This is an optional method, see Optional methods.

sudoedit

     The sudoedit method facilitates editing a file as a different user on the local host.  You could regard this as tramp's implementation of the sudoedit.  Contrary to the sudo method, all magic file name functions are implemented by single sudo ... commands.  The purpose is to make editing such a file as secure as possible; there must be no session running in the Emacs background which could be attacked from inside Emacs.

     Consequently, external processes are not implemented.

     The host name of such remote file names must represent the local host. Since the default value is already proper, it is recommended not to use any host name in the remote file name, like sudoedit,,/path/to/file or sudoedit,user@,/path/to/file.

     Like the sudo method, a sudoedit password expires after a predefined timeout.

ftp

     When tramp uses ftp, it forwards requests to whatever ftp program is specified by Ange FTP.  This external program must be capable of servicing requests from tramp.

smb

     This non-native tramp method connects via the Server Message Block (SMB) networking protocol to hosts running file servers that are typically based on Samba or MS Windows.

     Using smbclient requires a few tweaks when working with tramp:

     The first directory in the localname must be a share name on the remote host.

     Since some SMB share names end in the $ character, tramp must use $$ when specifying those shares to avoid environment variable substitutions.

     When tramp is not specific about the share name or uses the generic remote directory /, smbclient returns all available shares.

     Since SMB authentication is based on each SMB share, tramp prompts for a password even when accessing a different share on the same SMB host.  This prompting can be suppressed by Password handling.

     To accommodate user name/domain name syntax required by MS Windows authorization, tramp provides for an extended syntax in user%domain format (where user is the user name, % is the percent symbol, and domain is the MS Windows domain name).  An example:

          smb,daniel%BIZARRE@melancholia,/daniel$$/.emacs

     where user daniel connects as a domain user to the SMB host melancholia in the MS Windows domain BIZARRE to edit .emacs located in the home directory (share daniel$).

     Alternatively, for local WINS users (as opposed to domain users), substitute the domain name with the name of the local host in UPPERCASE as shown here:

          smb,daniel%MELANCHOLIA@melancholia,/daniel$$/.emacs

     where user daniel connects as local user to the SMB host melancholia in the local domain MELANCHOLIA to edit .emacs located in the home directory (share daniel$).

     The domain name and user name are optional for smbclient authentication.  When user name is not specified, smbclient uses the anonymous user (without prompting for password).  This behavior is unlike other tramp methods, where local user name is substituted.

     The smb method is unavailable if Emacs is run under a local user authentication context in MS Windows.  However such users can still access remote files using UNC file names instead of tramp:

          //melancholia/daniel$$/.emacs

     UNC file name specification does not allow the specification of a different user name for authentication like the smbclient can.

adb

     This method uses Android Debug Bridge program for accessing Android devices.  The Android Debug Bridge must be installed locally for tramp to work.  Some GNU/Linux distributions provide Android Debug Bridge as an installation package.  Alternatively, the program is installed as part of the Android SDK.  tramp finds the adb program either via the PATH environment variable or the absolute path set in the user option tramp-adb-program.

     tramp connects to Android devices with adb only when the user option tramp-adb-connect-if-not-connected is not nil.  Otherwise, the connection must be established outside Emacs.

     tramp does not require a host name part of the remote file name when a single Android device is connected to adb. tramp instead uses adb,, as the default name. adb devices, run in a shell outside Emacs, shows available host names.

     adb method normally does not need user name to authenticate on the Android device because it runs under the adbd process.  But when a user name is specified, however, tramp applies an su in the syntax.  When authentication does not succeed, especially on un-rooted Android devices, tramp displays login errors.

     For Android devices connected through TCP/IP, a port number can be specified using device#42 host name syntax or tramp can use the default value as declared in adb command.  Port numbers are not applicable to Android devices connected through USB.

GVFS-based external methods
===========================

GVFS is the virtual file system for the GNOME Desktop, https://en.wikipedia.org/wiki/GVFS.  Remote files on GVFS are mounted locally through FUSE and tramp uses this locally mounted directory internally.

Emacs uses the D-Bus mechanism to communicate with GVFS.  It must have been compiled with D-Bus support, see D-Bus (dbus).

The tramp-gvfs-enabled variable, being non-nil, signals that tramp can use GVFS-based methods.

afp

     This method is for connecting to remote hosts with the Apple Filing Protocol for accessing files on macOS volumes.  tramp access syntax requires a leading volume (share) name, for example: afp,user@host,/volume.

dav

davs

     dav method provides access to WebDAV files and directories based on standard protocols, such as HTTP.  davs does the same but with SSL encryption.  Both methods support the port numbers.

     Paths being part of the WebDAV volume to be mounted by GVFS, as it is common for OwnCloud or NextCloud file names, are not supported by these methods.  See method nextcloud for handling them.

gdrive

     Via the gdrive method it is possible to access your Google Drive online storage.  User and host name of the remote file name are your email address of the Google Drive credentials, like gdrive,john.doe@gmail.com,/.  These credentials must be populated in your Online Accounts application outside Emacs.

     Since Google Drive uses cryptic blob file names internally, tramp works with the display-name of the files.  This could produce unexpected behavior in case two files in the same directory have the same display-name, such a situation must be avoided.

mtp

     Media devices, like cell phones, tablets, cameras, can be accessed via the mtp method.  Just the device name is needed in order to specify the host in the file name.  However, the device must already be connected via USB, before accessing it.  Possible device names are visible via host name completion, see File name completion.

     Depending on the device type, the access could be read-only.  Some devices are accessible under different names in parallel, offering different parts of their file system.

     tramp does not require a host name as part of the remote file name when a single media device is connected.  tramp instead uses mtp,, as the default name.

nextcloud

     As the name indicates, the method nextcloud allows you to access OwnCloud or NextCloud hosted files and directories.  Like the gdrive method, your credentials must be populated in your Online Accounts application outside Emacs.  The method supports port numbers.

sftp

     This method uses sftp in order to securely access remote hosts.  sftp is a more secure option for connecting to hosts that for security reasons refuse ssh connections.

     When there is a respective entry in your ssh configuration, do not set the RemoteCommand option.

 -- User Option: tramp-gvfs-methods
     This user option is a list of external methods for GVFS. By default, this list includes afp, dav, davs, gdrive, mtp, nextcloud and sftp.  Other methods to include are ftp, http, https and smb.  These methods are not intended to be used directly as GVFS-based method.  Instead, they are added here for the benefit of Archive file names.

     If you want to use GVFS-based ftp or smb methods, you must add them to tramp-gvfs-methods, and you must disable the corresponding tramp package by setting tramp-ftp-method or tramp-smb-method to nil, respectively:

          (add-to-list 'tramp-gvfs-methods "ftp")
          (customize-set-variable 'tramp-ftp-method nil)

FUSE-based external methods
===========================

Besides GVFS, there are other virtual file systems using the FUSE interface.  Remote files are mounted locally through FUSE and tramp uses this locally mounted directory internally.  When possible, tramp maps the remote file names to their respective local file name, and applies the file name operation on them.  For some of the file name operations this is not possible, tramp emulates those operations otherwise.

rclone

     The program rclone enables accessing different system storages in the cloud, see https://rclone.org/ for a list of supported systems.  If the rclone program isn't found in your PATH environment variable, you can tell tramp its absolute path via the user option tramp-rclone-program.

     A system storage must be configured via the rclone config command, outside Emacs.  If you have configured a storage in rclone under a name storage (for example), you can access it via the remote file name

          rclone,storage,/path/to/file

     User names are part of the rclone configuration, and not needed in the remote file name.  If a user name is contained in the remote file name, it is ignored.

     Access via rclone is slow.  If you have an alternative method for accessing the system storage, you should use it. GVFS-based methods for example, methods gdrive and nextcloud.

sshfs

     On local hosts which have installed the sshfs client for mounting a file system based on the sftp subsystem of ssh, this method can be used, see https://github.com/libfuse/sshfs/blob/master/README.md.  If the sshfs program isn't found in your PATH environment variable, you can tell tramp its absolute path via the user option tramp-sshfs-program.

     All remote files are available via the local mount point. tramp aids in mounting the file system if it isn't mounted yet.  The remote file name syntax is

          sshfs,user@host#port,/path/to/file

     User name and port number are optional.  This method does not support password handling, the file system must either be mounted already, or the connection must be established passwordless via ssh keys.

     The mount point and mount arguments can be passed as connection properties, see Setup of sshfs method.

Selecting a default method
==========================

In a remote file name, the use of a default method is indicated by the pseudo method -, see File name syntax.

 -- User Option: tramp-default-method
     Default method is for transferring files.  The user option tramp-default-method sets it.  tramp uses this user option to determine the default method for remote file names that do not have one specified.

          (customize-set-variable 'tramp-default-method "ssh")

 -- User Option: tramp-default-method-alist
     Default methods for transferring files can be customized for specific user and host combinations through the user option tramp-default-method-alist.

     For example, the following two lines specify to use the ssh method for all user names matching john and the rsync method for all host names matching lily.  The third line specifies to use the su method for the user root on the host localhost.

          (add-to-list 'tramp-default-method-alist '("" "john" "ssh"))
          (add-to-list 'tramp-default-method-alist '("lily" "" "rsync"))
          (add-to-list 'tramp-default-method-alist
                       '("\\`localhost\\'" "\\`root\\'" "su"))

External methods performance faster for large files.  see Inline methods.  see External methods.

Choosing the access method also depends on the security environment. For example, rsh and telnet methods that use clear text password transfers are inappropriate for over the Internet connections.  Secure remote connections should use ssh that provide encryption.

Which method to use?
--------------------

tramp provides maximum number of choices for maximum flexibility.  Choosing which method depends on the hosts, clients, network speeds, and the security context.

Start by using an inline method.

External methods might be more efficient for large files, but most tramp users edit small files more often than large files.

Enable compression, tramp-inline-compress-start-size, for a performance boost for large files with inline methods.

Since ssh has become the most common method of remote host access and it has the most reasonable security protocols, use ssh method.  Typical ssh usage to edit the /etc/motd file on the otherhost:

     C-x C-f ssh,root@otherhost,/etc/motd RET

If ssh is unavailable for whatever reason, look for other obvious options.  For MS Windows, try the plink method (This shouldn't be needed with recent OpenSSH versions for MS Windows.  Use method sshx.).  For Kerberos, try krlogin.

For editing local files as su or sudo methods, try the shortened syntax of root:

     C-x C-f su,,/etc/motd RET

For editing large files, scp is faster than ssh. pscp is faster than plink.  But this speed improvement is not always true.

When copying large files between two different remote hosts via scp, set tramp-use-scp-direct-remote-copying to non-nil.

Selecting a default user
========================

 -- User Option: tramp-default-user
     A tramp file name can omit the user name part since tramp substitutes the currently logged-in user name.  However this substitution can be overridden with tramp-default-user. For example:

          (customize-set-variable 'tramp-default-user "root")

 -- User Option: tramp-default-user-alist
     Instead of a single default user, tramp-default-user-alist allows multiple default user values based on access method or host name combinations.  The alist can hold multiple values.  For example, to use the john as the default user for the domain somewhere.else only:

          (add-to-list 'tramp-default-user-alist
                       '("ssh" ".*\\.somewhere\\.else\\'" "john"))

     A Caution: tramp will override any default user specified in the configuration files outside Emacs, such as ~/.ssh/config. To stop tramp from applying the default value, set the corresponding alist entry to nil:

          (add-to-list 'tramp-default-user-alist
                       '("ssh" "\\`here\\.somewhere\\.else\\'" nil))

     The last entry in tramp-default-user-alist should be reserved for catch-all or most often used login.

          (add-to-list 'tramp-default-user-alist
                       '(nil nil "jonas") t)

Selecting a default host
========================

 -- User Option: tramp-default-host
     When host name is omitted, tramp substitutes the value from the tramp-default-host user option.  It is initially populated with the local host name where Emacs is running.  The default method, default user and default host can be overridden as follows:

          (custom-set-variables
           '(tramp-default-method "ssh")
           '(tramp-default-user "john")
           '(tramp-default-host "target"))

     With all defaults set, -,, will connect tramp to John's home directory on target via method ssh.

 -- User Option: tramp-default-host-alist
     Instead of a single default host, tramp-default-host-alist allows multiple default host values based on access method or user name combinations.  The alist can hold multiple values.  While tramp-default-host is sufficient in most cases, some methods, like adb, require defaults overwritten.

     The default host name for nspawn is .host.  Therefore, nspawn,, and sudo,, have the same effect.

Connecting to a remote host using multiple hops
===============================================

Multi-hops are methods to reach hosts behind firewalls or to reach the outside world from inside a bastion host.  With multi-hops, tramp can negotiate these hops with the appropriate user/host authentication at each hop.  All methods until now have been the single hop kind, where the start and end points of the connection did not have intermediate check points.

 -- User Option: tramp-default-proxies-alist
     tramp-default-proxies-alist specifies proxy hosts to pass through.  This user option is list of triples consisting of (HOST USER PROXY).

     The first match is the proxy host through which passes the file name and the target host matching USER@HOST.  HOST and USER are regular expressions or nil, interpreted as a regular expression which always matches.

     PROXY is a literal tramp file name whose local name part is ignored, and the method and user name parts are optional.

     The method must be an inline method (see Inline methods).  If PROXY is nil, no additional hop is required reaching USER@HOST.

     For example, to pass through the host bastion.your.domain as user bird to reach remote hosts outside the local domain:

          (add-to-list 'tramp-default-proxies-alist
                       '("\\." nil "ssh,bird@bastion.your.domain,"))
          (add-to-list 'tramp-default-proxies-alist
                       '("\\.your\\.domain\\'" nil nil))

     Note: add-to-list adds elements at the beginning of a list.  Therefore, most relevant rules must come last in the list.

     Proxy hosts can be cascaded in the alist.  If there is another host called jump.your.domain, which is the only host allowed to connect to bastion.your.domain, then:

          (add-to-list 'tramp-default-proxies-alist
                       '("\\`bastion\\.your\\.domain\\'"
                         "\\`bird\\'"
                         "ssh,jump.your.domain,"))

     PROXY can take patterns %h or %u for HOST or USER respectively.  Ports or domains, if they are part of a hop file name, are not expanded by those patterns.

     To login as root on remote hosts in the domain your.domain, but login as root is disabled for non-local access, then use this alist entry:

          (add-to-list 'tramp-default-proxies-alist
                       '("\\.your\\.domain\\'" "\\`root\\'" "ssh,%h,"))

     Opening sudo,randomhost.your.domain, first connects to randomhost.your.domain via ssh under your account name, and then performs sudo -u root on that host.

     It is key for the sudo method in the above example to be applied on the host after reaching it and not on the local host. tramp checks therefore, that the host name for such hops matches the host name of the previous hop.

     HOST, USER and PROXY can also take Lisp forms.  These forms when evaluated must return either a string or nil.

     To generalize (from the previous example): For all hosts, except my local one, first connect via ssh, and then apply sudo -u root:

          (add-to-list 'tramp-default-proxies-alist
                       '(nil "\\`root\\'" "ssh,%h,"))
          (add-to-list 'tramp-default-proxies-alist
                       `(,(regexp-quote (system-name)) nil nil))

Passing through hops involves dealing with restricted shells, such as rbash.  If tramp is made aware, then it would use them for proxies only.

 -- User Option: tramp-restricted-shell-hosts-alist
     An alist of regular expressions of hosts running restricted shells, such as rbash.  tramp will then use them only as proxies.

     To specify the bastion host from the example above as running a restricted shell:

          (add-to-list 'tramp-restricted-shell-hosts-alist
                       "\\`bastion\\.your\\.domain\\'")

Passing firewalls
=================

Sometimes, it is not possible to reach a remote host directly.  A firewall might be in the way, which could be passed via a proxy server.

Both OpenSSH and PuTTY support such proxy settings, using an HTTP tunnel via the CONNECT command (conforming to RFC 2616, 2817 specifications).  Proxy servers using HTTP 1.1 or later protocol support this command.

Tunneling with ssh
------------------

With ssh, you can use the ProxyCommand entry in ~/.ssh/config:

     Host host.other.domain
          ProxyCommand nc -X connect -x proxy.your.domain:3128 %h %p

nc is BSD's netcat program, which establishes HTTP tunnels. Any other program with such a feature could be used as well.

In the example, opening ssh,host.your.domain, passes the HTTP proxy server proxy.your.domain on port 3128.

Tunneling with PuTTY
--------------------

PuTTY does not need an external program, HTTP tunnel support is built-in.  In the PuTTY config program, create a session for host.your.domain.  In the Connection/Data entry, select the HTTP option, and add proxy.your.domain as Proxy hostname, and 3128 as Port.

Opening plinkx,host.your.domain, passes the HTTP proxy server proxy.your.domain on port 3128.

Using Non-Standard Methods
==========================

The tramp-methods variable currently has an exhaustive list of predefined methods.  Any part of this list can be modified with more suitable settings.  Refer to the Lisp documentation of that variable, accessible with C-h v tramp-methods RET.

In the ELPA archives, there are several examples of such extensions. They can be installed with Emacs's Package Manager.  This includes

incus-tramp
     Integration for Incus containers.  A container is accessed via incus,user@container,/path/to/file, user and container have the same meaning as with the docker method.

lxc-tramp
     Integration for LXC containers.  A container is accessed via lxc,container,/path/to/file, container has the same meaning as with the docker method.  A user specification is ignored.

lxd-tramp
     Integration for LXD containers.  A container is accessed via lxd,user@container,/path/to/file, user and container have the same meaning as with the docker method.

magit-tramp
     Browsing Git repositories with magit.  A versioned file is accessed via git,rev@root-dir,/path/to/file. rev is a Git revision, and root-dir is a virtual host name for the root directory, specified in magit-tramp-hosts-alist.

tramp-hdfs
     Access of a hadoop/hdfs file system.  A file is accessed via hdfs,user@node,/path/to/file, where user is the user that you want to use, and node is the name of the hadoop server.

vagrant-tramp
     Convenience method to access vagrant boxes.  It is often used in multi-hop file names like vagrantpostfixhopbox|sudo,box,/path/to/file, where box is the name of the vagrant box.

Selecting config files for user/host name completion
====================================================

tramp-completion-function-alist uses predefined files for user and host name completion (see File name completion).  For each method, it keeps a set of configuration files and a function that can parse that file.  Each entry in tramp-completion-function-alist is of the form (METHOD PAIR1 PAIR2 ...).

Each PAIR is composed of (FUNCTION FILE). FUNCTION is responsible for extracting user names and host names from FILE for completion.  There are two functions which access this variable:

 -- Function: tramp-get-completion-function method
     This function returns the list of completion functions for METHOD.

     Example:

          (tramp-get-completion-function "rsh")

               => ((tramp-parse-rhosts "/etc/hosts.equiv")
                   (tramp-parse-rhosts "~/.rhosts"))

 -- Function: tramp-set-completion-function method function-list
     This function sets FUNCTION-LIST as list of completion functions for METHOD.

     Example:

          (tramp-set-completion-function "ssh"
           '((tramp-parse-sconfig "/etc/ssh_config")
             (tramp-parse-sconfig "~/.ssh/config")))

               => ((tramp-parse-sconfig "/etc/ssh_config")
                   (tramp-parse-sconfig "~/.ssh/config"))

The following predefined functions parsing configuration files exist:

tramp-parse-rhosts

     This function parses files which are syntactical equivalent to ~/.rhosts.  It returns both host names and user names, if specified.

tramp-parse-shosts

     This function parses files which are syntactical equivalent to ~/.ssh/known_hosts.  Since there are no user names specified in such files, it can return host names only.

tramp-parse-sconfig

     This function returns the host nicknames defined by Host entries in ~/.ssh/config style files.

tramp-parse-shostkeys

     SSH2 parsing of directories /etc/ssh2/hostkeys/* and ~/ssh2/hostkeys/*.  Hosts are coded in file names hostkey_PORTNUMBER_HOST-NAME.pub.  User names are always nil.

tramp-parse-sknownhosts

     Another SSH2 style parsing of directories like /etc/ssh2/knownhosts/* and ~/ssh2/knownhosts/*.  This case, hosts names are coded in file names HOST-NAME.ALGORITHM.pub.  User names are always nil.

tramp-parse-hosts

     A function dedicated to /etc/hosts for host names.

tramp-parse-passwd

     A function which parses /etc/passwd for user names.

tramp-parse-etc-group

     A function which parses /etc/group for group names.

tramp-parse-netrc

     A function which parses ~/.netrc and ~/.authinfo-style files.

To keep a custom file with custom data in a custom structure, a custom function has to be provided.  This function must meet the following conventions:

 -- Function: my-tramp-parse file
     FILE must be either a file on the host, or nil.  The function must return a list of (USER HOST), which are taken as candidates for completion for user and host names.

     Example:

          (my-tramp-parse "~/.my-tramp-hosts")

               => ((nil "toto") ("daniel" "melancholia"))

Reusing passwords for several connections
=========================================

To avoid repeated prompts for passwords, consider native caching mechanisms, such as ssh-agent for ssh-like methods, or pageant for plink-like methods.

tramp offers alternatives when native solutions cannot meet the need.

Using an authentication file
----------------------------

The package auth-source.el, originally developed for No Gnus, reads passwords from different sources, see auth-source (auth).  The default authentication file is ~/.authinfo.gpg, but this can be changed via the user option auth-sources.

A typical entry in the authentication file:

     machine melancholia port scp login daniel password geheim

The port can take any tramp method (see Inline methods, see External methods).  Omitting port values matches all tramp methods.  Domain and ports, as used in tramp file name syntax, must be appended to the machine and login items:

     machine melancholia#4711 port davs login daniel%BIZARRE password geheim

For the methods doas, sudo, sudoedit and nspawn the password of the user requesting the connection is needed, and not the password of the target user (On the local host, run0 uses a graphical password agent.).  If these connections happen on the local host, an entry with the local user and local host is used:

     machine HOST port sudo login USER password secret

USER and HOST are the strings returned by (user-login-name) and (system-name).  If one of these methods is connected via a multi-hop (see Multi-hops), the credentials of the previous hop are used.

If no proper entry exists, the password is read interactively.  After successful login (verification of the password), Emacs offers to save a corresponding entry for further use by auth-source backends which support this.  This can be changed by setting the user option auth-source-save-behavior to nil.

Set auth-source-debug to t to debug messages.

Note that auth-source.el is not used for ftp connections, because tramp passes the work to Ange FTP.  If you want, for example, use your ~/.authinfo.gpg authentication file, you must customize ange-ftp-netrc-filename:

     (customize-set-variable 'ange-ftp-netrc-filename "~/.authinfo.gpg")

In case you do not want to use an authentication file for tramp passwords, use connection-local variables (see Connection Variables (emacs)) like this:

     (connection-local-set-profile-variables
      'remote-without-auth-sources '((auth-sources . nil)))

     (connection-local-set-profiles
      '(:application tramp) 'remote-without-auth-sources)

Caching passwords
-----------------

tramp can cache passwords as entered and reuse when needed for the same user or host name independent of the access method.

auth-source-cache-expiry (It overrides password-cache-expiry.) sets the duration (in seconds) the passwords are remembered.  Set auth-source-cache-expiry to nil to disable expiration.

Cached passwords are never saved permanently nor can they extend beyond the lifetime of the current Emacs session unless you confirm this interactively.

Set auth-source-do-cache to nil to disable password caching.

For connections which use a session-timeout, like sudo, doas and run0, the password cache is expired by tramp when the session expires (see Predefined connection information).  However, this makes only sense if the password cannot be retrieved from a persistent authentication file or store.

Reusing connection related information
======================================

For faster initial connection times, tramp stores previous connection properties in a file specified by the user option tramp-persistency-file-name.

The default file name for tramp-persistency-file-name is ~/.emacs.d/tramp.

tramp reads this file during Emacs startup, and writes to it when exiting Emacs.  Delete this file for tramp to recreate a new one on next Emacs startup.

Set tramp-persistency-file-name to nil to disable storing connections persistently.

When tramp detects a change in the operating system version in a remote host (via the command uname -sr), it flushes all connection related information for that host and creates a new entry.

Setting own connection related information
==========================================

For more precise customization, parameters specified by tramp-methods can be overwritten manually.

Set tramp-connection-properties to manually override tramp-methods.  Properties in this list are in the form (REGEXP PROPERTY VALUE).  REGEXP matches remote file names.  Use nil to match all. PROPERTY is the property's name, and VALUE is the property's value.

PROPERTY is any method specific parameter contained in tramp-methods.  The parameter key in tramp-methods is a symbol name tramp-<foo>.  To overwrite that property, use the string "<foo>" for PROPERTY.  For example, this changes the remote shell:

     (add-to-list 'tramp-connection-properties
                  (list (regexp-quote "ssh,user@randomhost.your.domain,")
                        "remote-shell" "/bin/ksh"))

     (add-to-list 'tramp-connection-properties
                  (list (regexp-quote "ssh,user@randomhost.your.domain,")
                        "remote-shell-login" '("-")))

The parameters tramp-remote-shell and tramp-remote-shell-login in tramp-methods now have new values for the remote host.

PROPERTY can also be any property found in tramp-persistency-file-name.

Relevant connection properties to override
------------------------------------------

Not all connection properties need to be changed.  The most relevant properties are listed here:

  * "login-program"

     The property "login-program" stores the program to be used to connect to the remote host.  Sometimes, the program might have another name on your host, or it might be located in another path.  In this case, you can overwrite the default value, which is special for every connection method.  It is used in all connection methods of tramp-sh.el.

  * "login-args"

     "login-args" specifies a list of lists of arguments to pass to "login-program".  Read the docstring of tramp-methods how to construct these lists.

  * "remote-shell"

     This property tells tramp which remote shell to apply on the remote host.  It is used in all connection methods of tramp-sh.el.  The default value is "/bin/sh".

  * "remote-shell-login"

     A property to be used in conjunction with "remote-shell".  It specifies, which shell argument triggers a login shell.  Its default value is "-l", but some shells, like ksh, prefer "-".

  * "session-timeout"

     All tramp-sh.el based methods accept the property "session-timeout".  This is the time (in seconds) after a connection is disabled for security reasons, and must be reestablished.  A value of nil disables this feature.  Most of the methods do not set this property except the sudo, doas and run0 methods, which use predefined values.

  * "~"
     "~user"

     This is the home directory on the remote host.  Setting this connection property helps especially for methods which cannot expand to a remote home directory, like adb, rclone and sshfs.  Home directories for an example.

  * "tmpdir"

     The temporary directory on the remote host.  If not specified, the default value is "/data/local/tmp" for the adb and androidsu methods, "/C$/Temp" for the smb method, and "/tmp" otherwise.  Temporary directory.

  * "posix"

     Connections using the smb method check, whether the remote host supports posix commands.  If the remote host runs Samba, it confirms this capability.  However, some very old Samba versions have errors in their implementation.  In order to suppress the posix commands for those hosts, the property "posix" should be set to nil.

     The default value of this property is t (not specified in tramp-methods).  If the remote host runs native MS Windows, this property has no effect.

  * "mount-point"

     The directory file name an FUSE-based file system is mounted on.  The default value of this property is "<TMP>/tramp.method.user@host#port" (not specified in tramp-methods).  Temporary directory.

  * "mount-args"
     "copyto-args"

     "moveto-args"

     "about-args"

     These properties keep optional flags to the different rclone operations.  See their default values in tramp-methods if you want to change their values.

How tramp finds and uses programs on the remote host
====================================================

tramp requires access to and rights to several commands on remote hosts: ls, test, find and cat.

Besides there are other required programs for Inline methods and External methods of connection.

To improve performance and accuracy of remote file access, tramp uses perl (or perl5) and grep when available.

 -- User Option: tramp-remote-path
     tramp-remote-path specifies which remote directory paths tramp can search for Remote programs.

     tramp uses standard defaults, such as /bin and /usr/bin, which are reasonable for most hosts.  To accommodate differences in hosts and paths, for example, /bin:/usr/bin on Debian GNU/Linux or /usr/xpg4/bin:/usr/ccs/bin:/usr/bin:/opt/developerstudio12.6/bin on Solaris, tramp queries the remote host with getconf
     PATH and updates the symbol tramp-default-remote-path.

     For instances where hosts keep obscure locations for paths for security reasons, manually add such paths to local .emacs as shown below for tramp to use when connecting.

          (add-to-list 'tramp-remote-path "/usr/local/perl/bin")

     Another way to find the remote path is to use the path assigned to the remote user by the remote host.  tramp does not normally retain this remote path after login.  However, tramp-own-remote-path preserves the path value, which can be used to update tramp-remote-path.

          (add-to-list 'tramp-remote-path 'tramp-own-remote-path)

     Note that this works only if your remote /bin/sh shell supports the login argument -l.

tramp-remote-path can also be set per host via connection-local variables, see Connection Variables (emacs). You can define your own search directories like this:

     (connection-local-set-profile-variables
      'remote-path-with-bin
      '((tramp-remote-path . ("~/bin" tramp-default-remote-path))))

     (connection-local-set-profile-variables
      'remote-path-with-apply-pub-bin
      '((tramp-remote-path . ("/appli/pub/bin" tramp-default-remote-path))))

     (connection-local-set-profiles
      '(:application tramp :machine "randomhost") 'remote-path-with-bin)

     (connection-local-set-profiles
      '(:application tramp :user "anotheruser" :machine "anotherhost")
      'remote-path-with-apply-pub-bin)

When remote search paths are changed, local tramp caches must be recomputed.  To force tramp to recompute afresh, call M-x tramp-cleanup-this-connection RET or friends (see Cleanup remote connections).

Remote shell setup hints
========================

Changing the default remote or local shell
------------------------------------------

By default, tramp uses the command /bin/sh for starting a shell on the remote host.  This can be changed by setting the connection property "remote-shell"; see Predefined connection information.  If you want, for example, use /usr/bin/zsh on a remote host, you might apply

     (add-to-list 'tramp-connection-properties
                  (list (regexp-quote "sshx,user@host,")
                        "remote-shell" "/usr/bin/zsh"))

This works only for connection methods which allow overriding the remote login shell, like sshx or plink.  See Inline methods and External methods for connection methods which support this.

This approach has also the advantage, that settings in tramp-sh-extra-args will be applied.  For zsh, the trouble with the shell prompt due to set zle options will be avoided. For bash, loading ~/.editrc or ~/.inputrc is suppressed.

Similar problems can happen with the local shell tramp uses to create a process.  By default, it uses the command /bin/sh for this, which could also be a link to another shell.  In order to overwrite this, you might apply

     (customize-set-variable 'tramp-encoding-shell "/usr/bin/zsh")

This uses also the settings in tramp-sh-extra-args.

Note: If you use an ssh-based method for connection, do not set the RemoteCommand option in your ssh configuration to something like screen.  If used, RemoteCommand must open an interactive shell on the remote host.  On the other hand, some ssh-based methods, like sshx or scpx, silently overwrite a RemoteCommand option of the configuration file.

Other remote shell setup hints
------------------------------

tramp checks for the availability of standard programs in the usual locations.  Common tactics include successively trying test -e, /usr/bin/test -e, and /bin/test -e.  ls -d is another approach.  But these approaches do not help with these new login patterns.

When tramp encounters two-factor logins or additional challenge questions, such as entering birth date or security code or passphrase, tramp needs a few more configuration steps to accommodate them.

The difference between a password prompt and a passphrase prompt is that the password for completing the login while the passphrase is for authorizing access to local authentication information, such as the ssh key.

There is no one configuration to accommodate all the variations in login security, especially not the exotic ones.  However, tramp provides a few tweaks to address the most common ones.

tramp-shell-prompt-pattern

     tramp-shell-prompt-pattern is for remote login shell prompt, which may not be the same as the local login shell prompt, shell-prompt-pattern.  Since most hosts use identical prompts, tramp sets a similar default value for both prompts.

tramp-password-prompt-regexp

tramp-otp-password-prompt-regexp

tramp-wrong-passwd-regexp

     tramp uses tramp-password-prompt-regexp to distinguish between prompts for passwords and prompts for passphrases. By default, tramp-password-prompt-regexp handles the detection in English language environments.  See a localization example below:

          (customize-set-variable
           'tramp-password-prompt-regexp
           (concat
            "^.*"
            (regexp-opt
             '("passphrase" "Passphrase"
               ;; English
               "password" "Password"
               ;; Deutsch
               "passwort" "Passwort"
               ;; Français
               "mot de passe" "Mot de passe")
             t)
            ".*:\0? *"))

     This user option is, by default, initialized from password-word-equivalents when tramp is loaded, and it is usually more convenient to add new passphrases to that user option instead of altering this user option.

     The user option tramp-otp-password-prompt-regexp has a similar purpose, but for one-time passwords.  Those passwords are not cached by tramp for reuse.

     Similar localization may be necessary for handling wrong password prompts, for which tramp uses tramp-wrong-passwd-regexp.

tramp-terminal-type

     tramp uses the user option tramp-terminal-type to set the remote environment variable TERM for the shells it runs. By default, it is "dumb", but this can be changed.  A dumb terminal is best suited to run the background sessions of tramp.  However, running interactive remote shells might require a different setting.  This can be achieved by tweaking the TERM environment variable in process-environment.

          (let ((process-environment
                 (cons "TERM=xterm-256color" process-environment)))
            (shell))

Determining a tramp session

     Sometimes, it is needed to identify whether a shell runs under tramp control.  The setting of environment variable TERM will help:

          if test "$TERM" = "dumb"; then
             ...
          fi

     Another possibility is to check the environment variable INSIDE_EMACS.  Like for all subprocesses of Emacs, this is set to the version of the parent Emacs process, see Interactive Shell (emacs). tramp adds its own package version to this string, which can be used for further tests in an inferior shell.  The string of that environment variable looks always like

          echo $INSIDE_EMACS
          => 27.2,tramp:2.4.5

tset and other questions

     To suppress inappropriate prompts for terminal type, tramp sets the TERM environment variable before the remote login process begins via the user option tramp-terminal-type (see above).  This will silence common tset related prompts.

     tramp's strategy for handling such prompts (commonly triggered from login scripts on remote hosts) is to set the environment variables so that no prompts interrupt the shell initialization process.

     An alternative approach is to configure tramp with strings that can identify such questions using tramp-actions-before-shell.  Example:

          (defconst my-tramp-prompt-regexp
            "Enter the birth date of your mother:\\s-*"
            "Regular expression matching my login prompt question.")

          (defun my-tramp-action (proc vec)
            "Enter \"19000101\" in order to give a correct answer."
            (save-window-excursion
              (with-current-buffer (tramp-get-connection-buffer vec)
                (tramp-message vec 6 "\n%s" (buffer-string))
                (tramp-send-string vec "19000101"))))

          (add-to-list 'tramp-actions-before-shell
                       '(my-tramp-prompt-regexp my-tramp-action))

     The regular expressions used in tramp-actions-before-shell must match the end of the connection buffer.  Due to performance reasons, this search starts at the end of the buffer, and it is limited to 256 characters backwards.

Conflicting names for users and variables in .profile

     When a user name is the same as a variable name in a local file, such as .profile, then tramp may send incorrect values for environment variables.  To avoid incorrect values, change the local variable name to something different from the user name.  For example, if the user name is FRUMPLE, then change the variable name to FRUMPLE_DIR.

Non-Bourne commands in .profile

     When the remote host's .profile is also used for shells other than Bourne shell, then some incompatible syntaxes for commands in .profile may trigger errors in Bourne shell on the host and may not complete client's tramp connections.

     One example of a Bourne shell incompatible syntax in .profile: using export FOO=bar instead of FOO=bar; export
     FOO.  After remote login, tramp will trigger an error during its execution of /bin/sh on the remote host because Bourne shell does not recognize the export command as entered in .profile.

     Likewise, (~) character in paths will cause errors because Bourne shell does not do (~) character expansions.

     One approach to avoiding these incompatibilities is to make all commands in ~/.shrc and ~/.profile Bourne shell compatible so tramp can complete connections to that remote. To accommodate using non-Bourne shells on that remote, use other shell-specific config files.  For example, bash can use ~/.bash_profile and ignore .profile.

Interactive shell prompt

     tramp redefines the remote shell prompt internally for robust parsing.  This redefinition affects the looks of a prompt in an interactive remote shell through commands, such as M-x shell RET.  Such prompts, however, can be reset to something more readable and recognizable using these environment variables.

     tramp sets the INSIDE_EMACS environment variable in the startup script file ~/.emacs_SHELLNAME.

     SHELLNAME is bash or equivalent shell names.  Change it by setting the environment variable ESHELL in the .emacs as follows:

          (setenv "ESHELL" "bash")

     Then re-set the prompt string in ~/.emacs_SHELLNAME as follows:

          # Reset the prompt for remote tramp shells.
          if [ "${INSIDE_EMACS/*tramp*/tramp}" == "tramp" ] ; then
             PS1="[\u@\h \w]$ "
          fi

     See Interactive Shell (emacs).

busybox / nc

     tramp's nc method uses the nc command to install and execute a listener as follows (see tramp-methods):

          $ nc -l -p 42

     The above command-line syntax has changed with busybox versions.  If nc refuses the -p parameter, then overwrite as follows:

          (add-to-list 'tramp-connection-properties
                       `(,(regexp-quote "192.168.0.1")
                         "remote-copy-args" (("-l") ("%r"))))

     where 192.168.0.1 is the remote host IP address (see Predefined connection information).

Ssh setup hints
===============

The most common tramp connection family is based on either ssh or scp of OpenSSH, or plink or pscp of PuTTY on MS Windows.  In the following, some configuration recommendations are given.

Using ssh config include for host name completion
-------------------------------------------------

OpenSSH configuration files can use an Include option for further configuration files.  Default tramp host name completion ignores this option.  However, you can configure this yourself.

Given, your ~/.ssh/config file contains the following option:

     Include ~/.ssh/conf.d/*

The following code snippet in your .emacs uses all files in that directory for host name completion:

     (tramp-set-completion-function
      "ssh" (append (tramp-get-completion-function "ssh")
                    (mapcar (lambda (file) `(tramp-parse-sconfig ,file))
                            (directory-files
                             "~/.ssh/conf.d/"
                             'full directory-files-no-dot-files-regexp))))

This code snippet does it for the ssh method.  If you replace "ssh" by "scp", it does it also for that method (or any other method you like).

Detection of session hangouts
-----------------------------

ssh sessions on the local host hang when the network is down.  tramp cannot safely detect such hangs.  OpenSSH can be configured to kill such hangs with the following settings in ~/.ssh/config:

     Host *
          ServerAliveInterval 5
          ServerAliveCountMax 2

The corresponding PuTTY configuration is in the Connection entry, Seconds between keepalives option.  Set this to 5. PuTTY does not have a configuration option equivalent to OpenSSH's ServerAliveCountMax.

Using ssh connection sharing
----------------------------

tramp uses the ControlMaster=auto OpenSSH option by default, if possible.  However, it overwrites ControlPath settings when initiating ssh sessions.  tramp does this to fend off a stall if a master session opened outside the Emacs session is no longer open.  That is why tramp prompts for the password again even if there is an ssh already open.

Some OpenSSH versions support a ControlPersist option, which allows you to set the ControlPath provided the variable tramp-ssh-controlmaster-options is customized as follows:

     (customize-set-variable
      'tramp-ssh-controlmaster-options
      (concat
       "-o ControlPath=/tmp/ssh-ControlPath-%%r@%%h:%%p "
       "-o ControlMaster=auto -o ControlPersist=yes"))

Note how %r, %h and %p must be encoded as %%r, %%h and %%p.

Using a predefined string in tramp-ssh-controlmaster-options, or puzzling an own string, happens only when user option tramp-use-connection-share is set to t.  If the ~/.ssh/config file is configured appropriately for the above behavior, then any changes to ssh can be suppressed with this nil setting:

     (customize-set-variable 'tramp-use-connection-share nil)

Sometimes, it is not possible to use OpenSSH's ControlMaster option for remote processes.  This could result in concurrent access to the OpenSSH socket when reading data by different processes, which could block Emacs.  In this case, setting tramp-use-connection-share to suppress disables shared access.  It is not needed to set this user option permanently to suppress, binding the user option prior calling make-process is sufficient.  tramp does this for esxample for compilation processes on its own.

tramp-use-connection-share should also be set to nil or suppress if you use the ProxyCommand or ProxyJump options in your ssh configuration.

In order to use the ControlMaster option, tramp must check whether the ssh client supports this option.  This is only possible on the local host, for the first hop.  tramp does not use this option on proxy hosts, therefore.

If you want to use this option also for the other hops, you must configure ~/.ssh/config on the proxy host:

     Host *
          ControlMaster      auto
          ControlPath        tramp.%C
          ControlPersist     no

Check the ssh_config(5) man page whether these options are supported on your proxy host.

On MS Windows, tramp-use-connection-share is set to nil by default, because the MS Windows and MSYS2 implementations of OpenSSH do not support this option properly.

In PuTTY, you can achieve connection sharing in the Connection/SSH entry, enabling the Share SSH connections if possible option.  tramp-use-connection-share must be set to nil.  If tramp-use-connection-share is set to t or suppress, plink is called with the option -share or -noshare, respectively.

Configure direct copying between two remote servers
---------------------------------------------------

tramp uses a temporary local copy when copying two files between different remote hosts via external methods.  This behavior is due to authentication problems tramp cannot handle sufficiently.  However, for scp connections this can be changed.  When a file shall be copied between two different remote hosts source and target, and

  - Variable tramp-use-scp-direct-remote-copying is non-nil,

  - Remote host source doesn't use the RemoteCommand option in ~/.ssh/config,

  - Remote host target shows the same host key when seen from the local host and from host source, and

  - scp running on host source can authenticate to host target without requiring a password,

tramp applies direct remote copying between hosts source and target like

     scp -p -T -R -q -r source:/path/to/file target:/path/to/another/file

This protects also your local temporary directory from overrun when copying large files.

If these conditions do not apply, and tramp-use-scp-direct-remote-copying is non-nil, the option -3 is used instead of -R.

When tramp uses direct remote copying, password caches are not consulted.

Issues with Cygwin and MS Windows ssh
-------------------------------------

This section is incomplete.  Please share your solutions.

MS Windows' ssh does not open a remote TTY.  Use the method sshx or scpx instead.  Furthermore, it cannot read a passphrase for ssh private keys.  Use the MS ssh-agent.

Cygwin's ssh works only with a Cygwin version of Emacs.  To check for compatibility: type M-x eshell RET, and start ssh test.host RET.  Incompatibilities trigger this message:

     Pseudo-terminal will not be allocated because stdin is not a terminal.

Some older versions of Cygwin's ssh work with the sshx access method.  Consult Cygwin's FAQ at https://cygwin.com/faq/ for details.

On the Emacs Wiki (https://www.emacswiki.org/emacs/SshWithNTEmacs) it is explained how to use the helper program fakecygpty to fix this problem.

When using the scpx access method, Emacs may call scp with MS Windows file naming, such as c:/foo.  But the version of scp that is installed with Cygwin does not know about MS Windows file naming, which causes it to incorrectly look for a host named c.

A workaround: write a wrapper script for scp to convert Windows file names to Cygwin file names.

When using the cygwin ssh-agent on MS Windows for password-less interaction, ssh methods depend on the environment variable SSH_AUTH_SOCK.  But this variable is not set when Emacs is started from a Desktop shortcut and authentication fails.

One workaround is to use an MS Windows based SSH Agent, such as the native MS ssh-agent or Pageant.  The latter is part of the PuTTY Suite of tools.

The fallback is to start Emacs from a shell.

FUSE setup hints
================

The FUSE file systems are mounted by default at "<TMP>/tramp.method.user@host#port". (Temporary directory)  Method is either "rclone" or "sshfs".  The user name and port number are optional.  If the file system is already mounted, it will be used as it is.  If the mount point does not exist yet, tramp creates this directory.

The mount point can be overwritten by the connection property "mount-point", see Predefined connection information. Example:

     (add-to-list 'tramp-connection-properties
                  `(,(regexp-quote "sshfs,user@host,")
                    "mount-point"
                    ,(expand-file-name "sshfs.user@host" user-emacs-directory)))

The user option tramp-fuse-unmount-on-cleanup, when set to non-nil, controls, whether a mount point is unmounted on connection cleanup or on Emacs exiting.

rclone setup
------------

The default arguments of the rclone operations mount, copyto, moveto and about are declared in the variable tramp-methods as method specific parameters.  Usually, they don't need to be overwritten.

If needed, these parameters can be overwritten as connection properties "mount-args", "copyto-args", "moveto-args" and "about-args", see Predefined connection information.  All of them are list of strings.

Be careful changing "--dir-cache-time", this could delay visibility of files.

sshfs setup
-----------

The method sshfs declares the mount arguments in the variable tramp-methods, passed to the sshfs command.  This is a list of list of strings, and can be overwritten by the connection property "mount-args", see Predefined connection information.

Additionally, it declares also the arguments for running remote processes, using the ssh command.  These don't need to be changed.

Android shell setup hints
=========================

tramp uses the adb method to access Android devices. Android devices provide a restricted shell access through an USB connection.  The local host must have the adb program installed.  Usually, it is sufficient to open the file adb,,/.  Then you can navigate in the file system via dired.

Alternatively, applications such as Termux or SSHDroid that run sshd process on the Android device can accept any ssh-based methods provided these settings are adjusted:

  * sh must be specified for remote shell since Android devices do not provide /bin/sh.  sh will then invoke whatever shell is installed on the device with this setting:

          (add-to-list 'tramp-connection-properties
                       (list (regexp-quote "192.168.0.26") "remote-shell" "sh"))

     where 192.168.0.26 is the Android device's IP address. (see Predefined connection information).

  * On the Android device the directory names are prefixed with an application specific prefix, which is /data/data/com.termux/files/usr/bin instead of /usr/bin in the Termux case.  You must adapt the file names in tramp-remote-path, for example via connection-local settings (see Connection Variables (emacs)):

          (connection-local-set-profile-variables
           'tramp-connection-local-termux-profile
           `((tramp-remote-path
              . ,(mapcar
          	(lambda (x)
          	  (if (stringp x) (concat "/data/data/com.termux/files" x) x))
          	(copy-tree tramp-remote-path)))))

          (connection-local-set-profiles
           '(:application tramp :machine "192.168.0.26")
           'tramp-connection-local-termux-profile)

  * When the Android device is not rooted, specify a writable directory for temporary files:

          (add-to-list 'tramp-connection-properties
                       (list (regexp-quote "192.168.0.26")
          		   "tmpdir" "/data/data/com.termux/files/home/tmp"))

  * Open a remote connection with the command C-x C-f ssh,192.168.0.26#2222, RET, where sshd is listening on port 2222.

     To add a corresponding entry to the ~/.ssh/config file (recommended), use this:

          Host android
               HostName 192.168.0.26
               User root
               Port 2222

     To use the host name android instead of the IP address shown in the previous example, fix the connection properties as follows:

          (add-to-list 'tramp-connection-properties
                       (list (regexp-quote "android") "remote-shell" "sh"))
          (add-to-list 'tramp-connection-properties
                       (list (regexp-quote "android")
          		   "tmpdir" "/data/data/com.termux/files/home/tmp"))
          (connection-local-set-profiles
           '(:application tramp :machine "android")
           'tramp-connection-local-termux-profile)

     Open a remote connection with the more concise command C-x C-f ssh,android, RET.

Kubernetes setup hints
======================

With the kubernetes method, containers in Kubernetes pods can be accessed.  The host name is a pod name returned by kubectl get pods, or CONTAINER.POD if an explicit container name shall be used.  Otherwise, the first container in a pod is used.

Sometimes, asynchronous processes for a host without a dedicated container name show a warning like Defaulted container "container1" out of: container1, container2.  This can be mitigated by setting the pod annotation kubectl.kubernetes.io/default-container to a proper value (container1 in this example).

tramp uses the default Kubernetes context and namespace.  If another context or namespace shall be used, configure the user options tramp-kubernetes-context and tramp-kubernetes-namespace.

Auto-save, File Lock and Backup configuration
=============================================

To avoid tramp from saving backup files owned by root to locations accessible to others, default backup settings in backup-directory-alist have to be altered.

Here's a scenario where files could be inadvertently exposed.  Emacs by default writes backup files to the same directory as the original files unless changed to another location, such as ~/.emacs.d/backups/.  Such a directory will also be used by default by tramp when using, say, a restricted file su,root@localhost,/etc/secretfile.  The backup file of the secretfile is now owned by the user logged in from tramp and not root.

When backup-directory-alist is nil (the default), such problems do not occur.

To ``turn off'' the backup feature for remote files and stop tramp from saving to the backup directory, use this:

     (add-to-list 'backup-directory-alist
                  (cons tramp-file-name-regexp nil))

Disabling backups can be targeted to just the su and sudo methods:

     (setq backup-enable-predicate
           (lambda (name)
             (and (normal-backup-enable-predicate name)
                  (not
                   (let ((method (file-remote-p name 'method)))
                     (when (stringp method)
                       (member method '("su" "sudo"))))))))

Another option is to create better backup file naming with user and host names prefixed to the file name.  For example, transforming /etc/secretfile to ~/.emacs.d/backups/!su:root@localhost:!etc!secretfile, set the tramp user option tramp-backup-directory-alist from the existing user option backup-directory-alist.

Then tramp backs up to a file name that is transformed with a prefix consisting of the DIRECTORY name.  This file name prefixing happens only when the DIRECTORY is an absolute local file name.

Example:

     (add-to-list 'backup-directory-alist
                  (cons "." "~/.emacs.d/backups/"))
     (customize-set-variable
      'tramp-backup-directory-alist backup-directory-alist)

The backup file name of su,root@localhost,/etc/secretfile would be

Just as for backup files, similar issues of file naming affect auto-saving remote files.  Auto-saved files are saved in the directory specified by the user option auto-save-file-name-transforms. By default this is set to the local temporary directory.  But in some versions of Debian GNU/Linux, this points to the source directory where the Emacs was compiled.  Reset such values to a valid directory.

Set auto-save-file-name-transforms to nil to save auto-saved files to the same directory as the original file.

Alternatively, set the user option tramp-auto-save-directory to direct all auto saves to that location.

If you want to suppress auto-saving of remote files at all, set user option remote-file-name-inhibit-auto-save to non-nil.

An alternative to auto-save-mode is auto-save-visited-mode.  In this mode, auto-saving is identical to explicit saving.  If you want to disable this behavior for remote files, set user option remote-file-name-inhibit-auto-save-visited to non-nil.

And still more issues to handle.  Since Emacs 28, file locks use a similar user option as auto-save files, called lock-file-name-transforms.  By default this user option is nil, meaning to keep file locks in the same directory as the original file.

If you change lock-file-name-transforms in order to keep file locks for remote files somewhere else, you will lose Emacs's feature to warn you, if a file is changed in parallel from different Emacs sessions, or via different remote connections.  Be careful with such settings.

Setting remote-file-name-inhibit-locks to non-nil prevents the creation of remote lock files at all.

Per default, tramp asks for confirmation if a root-owned remote backup, auto-save or lock file has to be written to your local temporary directory.  If you want to suppress this confirmation question, set user option tramp-allow-unsafe-temporary-files to t.

Protect remote files by encryption
==================================

Note: File encryption in tramp is experimental, don't use it in production systems!

Sometimes, it is desirable to protect files located on remote directories, like cloud storages.  In order to do this, you might instruct tramp to encrypt all files copied to a given remote directory, and to decrypt such files when accessing.  This includes both file contents and file names.

tramp does this transparently.  Although both files and file names are encrypted on the remote side, they are accessible inside Emacs as they wouldn't be transformed as such.

Internally, tramp uses the encfs package. Therefore, this feature is available only if this package is installed on the local host.  tramp does not keep and encfs
mountpoint permanently.  Instead, it encrypts / decrypts files and file names on the fly, using encfsctl.

 -- Command: tramp-crypt-add-directory name
     This command marks the existing remote directory NAME for encryption.  Files in that directory and all subdirectories will be encrypted before copying to, and decrypted after copying from that directory.  File and directory names will be also encrypted.

 -- User Option: tramp-crypt-encfs-option
     If a remote directory is marked for encryption, it is initialized via encfs the very first time a file in this directory is accessed.  This user option controls, which default encfs configuration option will be selected, it can be "--standard" or "--paranoia".  See the encfs(1) man page for details.

     However, tramp must adapt these configuration sets.  The chainedNameIV configuration option must be disabled; otherwise tramp couldn't handle file name encryption transparently.

A password protected encfs configuration file is created the very first time you access an encrypted remote directory.  It is kept in your user-emacs-directory with the url-encoded directory name as part of the basename, and encfs6.xml as suffix.  If you, for example, mark the remote directory nextcloud,user@host,/path/to/dir for encryption, the configuration file is saved as tramp-%2Fnextcloud%3Auser%40host%3A%2Fpath%2Fto%2Fdir%2F.encfs6.xml in user-emacs-directory.  Do not lose this file and the corresponding password; otherwise there is no way to decrypt your encrypted files.

 -- User Option: tramp-crypt-save-encfs-config-remote
     If this user option is non-nil (the default), the encfs configuration file .encfs6.xml is also kept in the encrypted remote directory.  It depends on you, whether you regard the password protection of this file as sufficient.  The advantage would be, that such a remote directory could be accessed by different Emacs sessions, different users, without presharing the configuration file between the users.

The command encfsctl, the workhorse for encryption / decryption, needs the configuration file password every call. Therefore, it is recommend to cache this password in Emacs.  This can be done using auth-sources, see Using an authentication file. An entry needs the url-encoded directory name as machine, your local user name as user, and the password.  The port is optional, if given it must be the string "crypt".  The example above would require the following entry in the authentication file ("yourname" is the result of (user-login-name)):

     machine %2Fnextcloud%3Auser%40host%3A%2Fpath%2Fto%2Fdir%2F \
             login yourname port crypt password geheim

If you use a remote file name with a quoted localname part, this localname and the corresponding file will not be encrypted / decrypted.  If you have an encrypted remote directory nextcloud,user@host,/path/to/dir, the command

     C-x d nextcloud,user@host,/path/to/dir

will show the directory listing with the plain file names, and the command

     C-x d nextcloud,user@host,/:/path/to/dir

will show the directory listing with the encrypted file names, and visiting a file will show its encrypted contents.  However, it is highly discouraged to mix encrypted and not encrypted files in the same directory.

 -- Command: tramp-crypt-remove-directory name
     This command should be used to indicate that files in name should no longer be encrypted.  Existing encrypted files and subdirectories will remain encrypted.

Using tramp
***********

tramp operates transparently, accessing remote files as if they are local.  However, tramp employs a formalized remote file naming syntax to perform its functions transparently.  This syntax consists of many parts specifying access methods, authentication, host names, and file names.  Ange FTP uses a similar syntax.

Unlike opening local files in Emacs, which are instantaneous, opening remote files in tramp is slower at first.  Sometimes there is a noticeable delay before the prompts for passwords or authentication appear in the minibuffer.  Hitting RET or other keys during this gap will be processed by Emacs.  This type-ahead facility is a feature of Emacs that may cause missed prompts when using tramp.

tramp file name conventions
===========================

method,host,/path/to/file opens file /PATH/TO/FILE on the remote host HOST, using the method METHOD.

prefixsshpostfixhopmelancholiapostfix.emacs
     For the file .emacs located in the home directory, on the host melancholia, using method ssh.

prefixsshpostfixhopmelancholia.danann.netpostfix.emacs
     For the file .emacs specified using the fully qualified domain name of the host.

prefixsshpostfixhopmelancholiapostfix~/.emacs
     For the file .emacs specified using the ~, which is expanded.

prefixsshpostfixhopmelancholiapostfix~daniel/.emacs
     For the file .emacs located in daniel's home directory on the host, melancholia.  The ~<user> construct is expanded to the home directory of that user on the remote host.

prefixsshpostfixhopmelancholiapostfix/etc/squid.conf
     For the file /etc/squid.conf on the host melancholia.

HOST can take IPv4 or IPv6 address, as in ssh,127.0.0.1,.emacs or ssh,ipv6prefix::1ipv6postfix,.emacs.

By default, tramp will use the current local user name as the remote user name for log in to the remote host.  Specifying a different name using the proper syntax will override this default behavior: method,user@host,path/to/file.

ssh,daniel@melancholia,.emacs is for file .emacs in daniel's home directory on the host, melancholia, accessing via method ssh.

For specifying port numbers, affix #<port> to the host name.  For example: ssh,daniel@melancholia#42,.emacs.

All method, user name, host name, port number and local name parts are optional, see Default Method, see Default User, see Default Host.

File name completion
====================

tramp can complete the following tramp file name components: method names, user names, host names, and file names located on remote hosts.

For example, type C-x C-f prefixwithspace s TAB, tramp completion choices show up as

       sbin/
       prefixhopscppostfix
       prefixhopscpxpostfix
       prefixhopsftppostfix
       prefixhopsgpostfix

       prefixhopsmbpostfix
       srv/
       prefixhopsshpostfix
       prefixhopsshxpostfix
       prefixhopsupostfix

       prefixhopsudopostfix
       sys/

prefixhopsshpostfixhop is a possible completion for the respective method, and sbin/ stands for the directory /sbin on your local host.

Type s h postfixhop for the minibuffer completion to prefixsshpostfixhop.  Typing TAB shows host names tramp extracts from ~/.ssh/config file, for example:

       prefixhopsshpostfixhop127.0.0.1postfix
       prefixhopsshpostfixhop192.168.0.1postfix

       prefixhopsshpostfixhopipv6prefix::1ipv6postfixpostfix
       prefixhopsshpostfixhoplocalhostpostfix

       prefixhopsshpostfixhopmelancholia.danann.netpostfix
       prefixhopsshpostfixhopmelancholiapostfix

Choose a host from the above list and then continue to complete file names on that host.

When the configuration (see Customizing Completion) includes user names, then the completion lists will account for the user names as well.

Results from auth-sources search (see Using an authentication file) are added to the completion candidates.  This search could be annoying, for example due to a passphrase request of the ~/.authinfo.gpg authentication file.  The user option tramp-completion-use-auth-sources controls, whether such a search is performed during completion.

Remote hosts previously visited or hosts whose connections are kept persistently (see Connection caching) will be included in the completion lists.  If you want to suppress this completion because there are invalid entries in the persistency file, for example if the host configuration changes often, or if you plug your laptop to different networks frequently, you can set the user option tramp-completion-use-cache to nil.

After remote host name completion comes completion of file names on the remote host.  It works the same as with local host file completion except that killing with double-slash // kills only the file name part of the tramp file name syntax.  A triple-slash stands for the default behavior. See Minibuffer File (emacs).

Example:

     C-x C-f ssh,melancholia,/usr/local/bin//etc TAB
          -| ssh,melancholia,/etc

     C-x C-f ssh,melancholia,//etc TAB
          -| ssh,melancholia,/etc

     C-x C-f ssh,melancholia,/usr/local/bin///etc TAB
          -| /etc

Declaring multiple hops in the file name
========================================

tramp file name syntax can accommodate ad-hoc specification of multiple proxies without using tramp-default-proxies-alist configuration setup (see Multi-hops).

Each proxy is specified using the same syntax as the remote host specification minus the file name part.  Each hop is separated by a |.  Chain the proxies from the starting host to the destination remote host name and file name.  For example, hopping over a single proxy bird@bastion to a remote file on you@remotehost:

     C-x C-f prefixsshpostfixhopbird@bastion|
     sshpostfixhopyou@remotehostpostfix/path RET

Each involved method must be an inline method (see Inline methods).

tramp adds the ad-hoc definitions as an ephemeral record to tramp-default-proxies-alist, which are available for reuse during that Emacs session.  Subsequent tramp connections to the same remote host can then use the abbreviated form ssh,you@remotehost,/path.

 -- User Option: tramp-show-ad-hoc-proxies
     If this user option is non-nil, ad-hoc definitions are kept in remote file names instead of showing the abbreviations.  This is useful if the ad-hoc proxy definition shall be used in further Emacs sessions, kept in configuration files of recentf and other packages.

     A non-nil setting of this option has effect only if set before the connection is established.

          (customize-set-variable 'tramp-show-ad-hoc-proxies t)

Ad-hoc definitions are removed from tramp-default-proxies-alist via the command M-x tramp-cleanup-all-connections RET (see Cleanup remote connections).

 -- User Option: tramp-save-ad-hoc-proxies
     For ad-hoc definitions to be saved automatically in tramp-default-proxies-alist for future Emacs sessions, set tramp-save-ad-hoc-proxies to non-nil.  The resulting user option tramp-default-proxies-alist is saved in your .emacs file.

     If you use saved configuration files with abbreviated ad-hoc proxy definitions on another host, for example by distribution of the recentf-save-file, you must distribute your .emacs file as well.

          (customize-set-variable 'tramp-save-ad-hoc-proxies t)

Ad-hoc proxies can take patterns %h or %u like in tramp-default-proxies-alist.  The following file name expands to user root on host remotehost, starting with an ssh session on host remotehost: sshpostfixhop%h|su,remotehost,.

On the other hand, if a trailing hop does not specify a host name, the host name of the previous hop is reused.  Therefore, the following file name is equivalent to the previous example: sshpostfixhopremotehost|su,,.

 -- User Option: tramp-completion-multi-hop-methods
     When this list includes the last method in a multi-hop connection, the remote host will be queried for a list of completion candidates.  This can, for example, provide a list of running docker or podman containers on the remote host.

          (customize-set-variable 'tramp-completion-multi-hop-methods
           `(,tramp-docker-method ,tramp-podman-method))

A common use case for ad-hoc specifications is to visit a file or a directory with proper permissions, for example with the sudo method.  The command tramp-revert-buffer-with-sudo supports this.

 -- Command: tramp-revert-buffer-with-sudo
     This command shows the current buffer with sudo permissions. The buffer must either visit a file, or a directory (dired-mode).

 -- User Option: tramp-file-name-with-method
     The method tramp-revert-buffer-with-sudo shows an alternate buffer.  It defaults to sudo, other valid methods are su, doas, run0, and ksu.

          (customize-set-variable 'tramp-file-name-with-method "doas")

These methods apply the user root as default.  If another user shall be taken, add a proper rule to the user option tramp-default-user-alist (see Default User):

     (add-to-list 'tramp-default-user-alist '("sudo" "remotehost" "admin"))

Expanding ~ to home directory
=============================

Home directories on remote hosts can be typed as tilde ~.  If possible, they are expanded to the remote user's home directory on the remote host.  Example:

     ssh,user@host,~
     => ssh,user@host,/home/user

This works in general for ssh-like methods, and for sudoedit.  These methods allow also the home directory expansion for another user, like

     sudoedit,,~otheruser
     => sudoedit,root@localhost,/home/otheruser

For other methods, a home directory can be expanded only if supported. This happens for example for the sftp method.  Methods, which require a share directory in the remote file name (afp, smb), use the value of this share directory as home directory:

     smb,user@host,~
     => smb,user@host,/share

Since tramp cannot know in advance which share directory is intended to use, this expansion can be applied only when a share directory has been used already.

The methods adb, rclone and sshfs do not support home directory expansion at all.  However, tramp keeps the home directory in the cache.  Therefore, those methods can be configured to expand a home directory via a connection property, see Predefined connection information.  Example:

     (add-to-list 'tramp-connection-properties
                  (list (regexp-quote "sshfs,user@randomhost.your.domain,")
                        "~user" "/home/user"))

When your remote file name does not contain a user part, the connection property "~" must be used instead.

Integration with other Emacs packages
=====================================

tramp supports starting new running processes on the remote host for discovering remote file names.  Emacs packages on the remote host need no specific modifications for tramp's use.

This type of integration does not work with the ftp method, and does not support the pty association as specified in start-file-process.

process-file and start-file-process work on the remote host when the variable default-directory is remote:

     (let ((default-directory "/ssh:remote.host:"))
       (start-file-process "grep" (get-buffer-create "*grep*")
                           "/bin/sh" "-c" "grep -e tramp *"))

For a local process, process-file returns either the exit code of the process, or a string describing a signal, when the process has been interrupted.  Since it cannot be determined reliably whether a remote process has been interrupted, process-file will always returns the exit code for it.  When the user option process-file-return-signal-string is non-nil, process-file treats all exit codes greater than 128 as an indication that the process has been interrupted, and returns a corresponding string.

This remote process handling does not apply to GVFS (see GVFS-based methods) because the remote file system is mounted on the local host and tramp accesses it by changing the default-directory.

tramp starts a remote process when a command is executed in a remote file or directory buffer.  As of now, these packages have been integrated to work with tramp: shell.el, eshell.el, compile.el (commands like compile and grep) and gud.el (gdb or perldb).

tramp always modifies the INSIDE_EMACS environment variable for remote processes.  By default, this environment variable shows the Emacs version.  tramp adds its own version string, so it looks like 27.2,tramp:2.4.5.1.  However, other packages might also add their name to this environment variable, like 27.2,comint,tramp:2.4.5.1.

For tramp to find the command on the remote, it must be accessible through the default search path as setup by tramp upon first connection.  Alternatively, use an absolute path or extend tramp-remote-path (see Remote programs):

     (add-to-list 'tramp-remote-path "~/bin")
     (add-to-list 'tramp-remote-path "/appli/pub/bin")

Customize user option tramp-remote-process-environment to suit the remote program's environment for the remote host. tramp-remote-process-environment is a list of strings structured similar to process-environment, where each element is a string of the form ENVVARNAME=VALUE.

To avoid any conflicts with local host environment variables set through local configuration files, such as ~/.profile, use ENVVARNAME= to unset them for the remote environment.

Use add-to-list to add entries:

     (add-to-list 'tramp-remote-process-environment "JAVA_HOME=/opt/java")

Modifying or deleting already existing values in the tramp-remote-process-environment list may not be feasible on restricted remote hosts.  For example, some system administrators disallow changing HISTORY environment variable.  To accommodate such restrictions when using tramp, fix the tramp-remote-process-environment by the following code in the local .emacs file:

     (let ((process-environment tramp-remote-process-environment))
       (setenv "HISTORY" nil)
       (setq tramp-remote-process-environment process-environment))

Setting the ENV environment variable instructs some shells to read an initialization file.  By default, tramp disables this.  You can override this behavior by evaluating

     (let ((process-environment tramp-remote-process-environment))
       (setenv "ENV" "$HOME/.profile")
       (setq tramp-remote-process-environment process-environment))

In addition to tramp-remote-process-environment, you can set environment variables for individual remote process calls by let-binding process-environment.  tramp applies any entries not present in the global default value of process-environment (overriding tramp-remote-process-environment settings, if they conflict). For example:

     (let ((process-environment (cons "HGPLAIN=1" process-environment)))
       (process-file ...))

Let-binding in this way works regardless of whether the process to be called is local or remote, since tramp would add just the HGPLAIN setting and local processes would take whole value of process-environment along with the new value of HGPLAIN.

For integrating other Emacs packages so tramp can execute remotely, please file a bug report.  See Bug Reports.

Running remote programs that create local X11 windows
-----------------------------------------------------

To allow a remote program to create an X11 window on the local host, set the DISPLAY environment variable for the remote host as follows in the local .emacs file:

     (add-to-list 'tramp-remote-process-environment
                  (format "DISPLAY=%s" (getenv "DISPLAY")))

(getenv "DISPLAY") should return a recognizable name for the local host that the remote host can redirect X11 window interactions.  If querying for a recognizable name is not possible for whatever reason, then replace (getenv "DISPLAY") with a hard-coded, fixed name.  Note that using :0 for X11 display name here will not work as expected.

An alternate approach is specify ForwardX11 yes or ForwardX11Trusted yes in ~/.ssh/config on the local host.  Furthermore, set tramp-use-connection-share to nil (see Using ssh connection sharing), in order to avoid unwanted side effects.

Managing remote shell history
-----------------------------

Due to the remote shell saving tilde expansions triggered by tramp, the shell history file is probably growing rapidly. tramp can suppress this behavior with the user option tramp-histfile-override.  When set to t, environment variable HISTFILE is unset, and environment variables HISTFILESIZE and HISTSIZE are set to 0.  Don't use this with bash 5.0.0 that version has a bug which causes bash to die.

Alternatively, tramp-histfile-override can be a string. The environment variable HISTFILE is then set to this file name.  Be careful if using /dev/null; this might result in undesired results when using bash as remote shell.

Another approach is to completely disable tramp's handling of the HISTFILE by setting tramp-histfile-override to nil.  In this case, saving history can be turned off by putting this shell code in .bashrc or .kshrc:

     if [ -f $HOME/.sh_history ] ; then
        /bin/rm $HOME/.sh_history
     fi
     if [ "${HISTFILE-unset}" != "unset" ] ; then
        unset HISTFILE
     fi
     if [ "${HISTSIZE-unset}" != "unset" ] ; then
        unset HISTSIZE
     fi

For ssh-based method, add the following line to your ~/.ssh/environment:

     HISTFILE=/dev/null

Running shell on a remote host
------------------------------

Set explicit-shell-file-name to the appropriate shell name when using tramp between two hosts with different operating systems, such as windows-nt and gnu/linux.  This option ensures the correct name of the remote shell program.

When explicit-shell-file-name is equal to nil, calling shell interactively will prompt for a shell name.

You can use connection-local variables for setting different values of explicit-shell-file-name for different remote hosts. See Connection Variables (emacs).

     (connection-local-set-profile-variables
      'remote-bash
      '((explicit-shell-file-name . "/bin/bash")
        (explicit-bash-args . ("-i"))))

     (connection-local-set-profile-variables
      'remote-ksh
      '((explicit-shell-file-name . "/bin/ksh")
        (explicit-ksh-args . ("-i"))))

     (connection-local-set-profiles
      '(:application tramp :protocol "ssh" :machine "localhost")
      'remote-bash)

     (connection-local-set-profiles
      `(:application tramp :protocol "sudo"
        :user "root" :machine ,(system-name))
      'remote-ksh)

The command shell reads the remote history file in order to to initialize the history input ring.  You can set the user option shell-history-file-name in order to specify which remote history file is taken, or whether to suppress this at all.  It accepts the same values as tramp-histfile-override, see Managing remote shell history. shell-history-file-name accepts also connection-local values in shell buffers.

Running shell-command on a remote host
--------------------------------------

shell-command executes commands synchronously or asynchronously on remote hosts and displays output in buffers on the local host.  Example:

     C-x C-f sudo,, RET
     M-& tail -f /var/log/syslog.log RET

tail command outputs continuously to the local buffer whose name is the value of the variable shell-command-buffer-name-async.

M-x auto-revert-tail-mode RET runs similarly showing continuous output.

shell-command uses the user option shell-file-name and the variable shell-command-switch in order to determine which shell to run.  For remote hosts, their default values are /bin/sh and -c, respectively (except for the adb method, which uses /system/bin/sh).  Like the variables in the previous section, these variables can be changed via connection-local variables.

tramp cares about the user option async-shell-command-width for asynchronous shell commands.  It specifies the number of display columns for command output.  For synchronous shell commands, a similar effect can be achieved by adding the environment variable COLUMNS to tramp-remote-process-environment.

Running eshell on a remote host
-------------------------------

tramp is integrated into eshell.el, which enables interactive eshell sessions on remote hosts at the command prompt. You must add the module eshell-tramp to eshell-modules-list.  Here's a sample interaction after opening M-x eshell RET on a remote host:

     ~ $ cd sudo,,/etc RET
     sudo,root@host,/etc $ hostname RET
     host
     sudo,root@host,/etc $ id RET
     uid=0(root) gid=0(root) groups=0(root)
     sudo,root@host,/etc $ find-file shadow RET
     #<buffer shadow>
     sudo,root@host,/etc $

eshell added custom su and sudo commands that set the default directory correctly for the *eshell* buffer. tramp silently updates tramp-default-proxies-alist with an entry for this directory (see Multi-hops):

     ~ $ cd ssh,user@remotehost,/etc RET
     ssh,user@remotehost,/etc $ find-file shadow RET
     File is not readable: ssh,user@remotehost,/etc/shadow
     ssh,user@remotehost,/etc $ sudo find-file shadow RET
     #<buffer shadow>

     ssh,user@remotehost,/etc $ su - RET
     su,root@remotehost,/root $ id RET
     uid=0(root) gid=0(root) groups=0(root)
     su,root@remotehost,/root $

Running a debugger on a remote host
-----------------------------------

gud.el provides a unified interface to symbolic debuggers (see Debuggers (emacs)). tramp can run debug on remote hosts by calling gdb with a remote file name:

     M-x gdb RET
     Run gdb (like this): gdb -i=mi ssh,host,~/myprog RET

Since the remote gdb and gdb-inferior processes do not belong to the same process group on the remote host, there will be a warning, which can be ignored:

     &"warning: GDB: Failed to set controlling terminal: Operation not permitted\n"

As consequence, there will be restrictions in I/O of the process to be debugged.

Relative file names are based on the remote default directory.  When myprog.pl exists in ssh,host,/home/user, valid calls include:

     M-x perldb RET
     Run perldb (like this): perl -d myprog.pl RET

Just the local part of a remote file name, such as perl -d /home/user/myprog.pl, is not possible.

Arguments of the program to be debugged must be literal, can take relative or absolute paths, but not remote paths.

Running remote processes on MS Windows hosts
--------------------------------------------

winexe runs processes on a remote MS Windows host, and tramp can use it for process-file and start-file-process.

tramp-smb-winexe-program specifies the local winexe command.  Powershell V2.0 on the remote host is required to run processes triggered from tramp.

explicit-shell-file-name and explicit-*-args have to be set properly so M-x shell RET can open a proper remote shell on a MS Windows host.  To open cmd, set it as follows:

     (setq explicit-shell-file-name "cmd"
           explicit-cmd-args '("/q"))

To open powershell as a remote shell, use this:

     (setq explicit-shell-file-name "powershell"
           explicit-powershell-args '("-file" "-"))

Remote process connection type
------------------------------

Asynchronous processes behave differently based on whether they use a pseudo tty or not.  This is controlled by the variable process-connection-type, which can be t or pty (use a pseudo tty), or nil or pipe (don't use one). tramp is based on running shells on the remote host, which requires a pseudo tty.  Therefore, it declares the variable tramp-process-connection-type, which carries this information for remote processes.  Its default value is t, and there is no need to change it.  The name of the remote pseudo tty is returned by the function process-tty-name.

If a remote process, started by start-file-process, should not use a pseudo tty, this can be requested by setting process-connection-type to nil or pipe.  There is still a pseudo tty for the started process, but some terminal properties are changed, like suppressing translation of carriage return characters into newline.

The function make-process allows controlling this explicitly by using the :connection-type keyword.  If this keyword is not used, the value of process-connection-type is applied instead.

Process properties of asynchronous remote processes
---------------------------------------------------

When available, tramp adds process properties to process objects of asynchronous properties.  However, it is not guaranteed that all these properties are set.

  * remote-tty

     This is the name of the terminal a PROCESS uses on the remote host, i.e., it reads and writes on.

  * remote-pid

     The process id of the command executed on the remote host.  This is used when sending signals remotely.

  * remote-command

     The remote command which has been invoked via make-process or start-file-process, a list of strings (program and its arguments).  This does not show the additional shell sugar tramp makes around the commands, in order to see this you must inspect tramp traces.

The functions list-system-processes and process-attributes return information about system processes on the respective remote host.  In order to retrieve this information, they use the command ps, driven by the following constants:

 -- Constant: tramp-process-attributes-ps-args
     This is a list of arguments (strings) ps is called with. The default value is appropriate for GNU/Linux remote hosts.

 -- Constant: tramp-process-attributes-ps-format
     This is a list of cons cells (KEY . TYPE) for interpretation of the ps output.  KEY is a key used in the process-attributes output plus the key pid, and TYPE is the respective value returned by ps.  It can be

     * numberp   --- a number
     * stringp   --- a string without spaces
     * NUMBER
     --- a string of NUMBER width, can contain spaces
     * nil   --- a string until end of line

     The default value is appropriate for GNU/Linux remote hosts.

If, for example, tramp-process-attributes-ps-args is declared as ("-eww" "-o" "pid,euid,euser,egid,egroup,comm:40,state"), the output of the respective ps command would look like

         PID  EUID EUSER     EGID EGROUP   COMMAND                                  S
           1     0 root         0 root     systemd                                  S
        1610     0 root         0 root     NFSv4 callback                           S
        ...

The corresponding tramp-process-attributes-ps-format has the value

     ((pid . numberp) (euid . numberp) (user . stringp)
      (egid . numberp) (group . stringp) (comm . 40) (state . stringp))

The default values for tramp-process-attributes-ps-args and tramp-process-attributes-ps-format can be overwritten by connection-local variables. See Connection Variables (emacs). This is already done by tramp for the adb method, see tramp-adb-connection-local-default-ps-profile and tramp-adb-connection-local-default-ps-variables.

There are three further predefined sets of connection-local variables for remote BSD systems, for remote macOS systems, and for a remote ps command implemented with busybox.  These are called tramp-connection-local-*-ps-profile and tramp-connection-local-*-ps-variables.  Use them like

     (connection-local-set-profiles
      '(:application tramp :machine "mybsdhost")
      'tramp-connection-local-bsd-ps-profile)

If you want to see a listing of remote system processes when calling proced, set user option proced-show-remote-processes to non-nil, or invoke that command with a negative argument like C-u - M-x proced RET when your buffer has a remote default-directory.

Improving performance of asynchronous remote processes
------------------------------------------------------

tramp's implementation of make-process and start-file-process requires a serious overhead for initialization, every process invocation.  This is needed for handling interactive dialogs when connecting the remote host (like providing a password), and initial environment setup.

Sometimes, this is not needed.  Instead of starting a remote shell and running the command afterwards, it is sufficient to run the command directly.  tramp supports this by an alternative implementation of make-process and start-file-process. This is triggered by the connection-local variable tramp-direct-async-process, See Connection Variables (emacs), which must be set to a non-nil value.  Example:

     (connection-local-set-profile-variables
      'remote-direct-async-process
      '((tramp-direct-async-process . t)))

     (connection-local-set-profiles
      '(:application tramp :machine "remotehost")
      'remote-direct-async-process)

This enables direct async processes for the host remotehost. If you want to enable direct async processes for all remote hosts connected via the same method (e.g., ssh), use instead

     (connection-local-set-profiles
      '(:application tramp :protocol "ssh")
      'remote-direct-async-process)

Using direct asynchronous processes in tramp is not possible, if the remote host is connected via multiple hops (see Multi-hops).  In this case, tramp falls back to its classical implementation.

Furthermore, this approach has the following limitations:

  * It works only for some connection methods defined in tramp-adb.el, tramp-container.el, tramp-sh.el and tramp-sshfs.el.

  * It does not support interactive user authentication.  With ssh-based methods, this can be avoided by using a password agent like ssh-agent, using public key authentication, or using ControlMaster options.

  * It cannot be applied for ssh-based methods, which use the RemoteCommand option.

  * It cannot be killed via interrupt-process.

  * It does not report the remote terminal name via process-tty-name.

  * It does not set process property remote-pid.  Consequently, signals cannot be sent to that remote process; they are sent to the local process instead, which establishes the connection.

  * It fails, when the command is too long.  This can happen on directories with a long directory name, or when the remote PATH and/or other environment variables, which must be set, are too long.

In order to gain even more performance, it is recommended to bind tramp-verbose to 0 when running make-process or start-file-process.  Furthermore, you might set tramp-use-connection-share to nil in order to bypass tramp's handling of the ControlMaster options, and use your own settings in ~/.ssh/config, see Using ssh connection sharing.

Note: In previous tramp versions this was triggered by the connection property "direct-async-process".  This is still supported but deprecated, and it will be removed in a future tramp version.

Note: For the ssh and scp methods, tramp does not faithfully pass binary sequences on to the process.  You can change this by changing the respective connection argument (see Predefined connection information) via

     (add-to-list 'tramp-connection-properties (list "/ssh:" "direct-async" t))

Cleanup remote connections
==========================

tramp provides several ways to flush remote connections.

 -- Command: tramp-cleanup-connection vec &optional keep-debug keep-password
     This command flushes all connection related objects.  VEC is the internal representation of a remote connection.  When called interactively, this command lists active remote connections in the minibuffer.  Each connection is of the format method,user@host,.

     Flushing remote connections also cleans the password cache (see Password handling), file cache, connection cache (see Connection caching), and recentf cache (see File Conveniences (emacs)). It also deletes session timers (see Predefined connection information) and connection buffers.

     If KEEP-DEBUG is non-nil, the debug buffer is kept.  A non-nil KEEP-PASSWORD preserves the password cache.

 -- Command: tramp-cleanup-this-connection
     Flushes the current buffer's remote connection objects, the same as in tramp-cleanup-connection.

 -- Command: tramp-cleanup-all-connections
     Flushes all active remote connection objects, the same as in tramp-cleanup-connection.  This command removes also ad-hoc proxy definitions (see Ad-hoc multi-hops).

 -- Command: tramp-cleanup-all-buffers
     Just as for tramp-cleanup-all-connections, all remote connections and ad-hoc proxy definition are cleaned up in addition to killing all buffers related to remote connections.

 -- Command: tramp-cleanup-some-buffers
     Similar to tramp-cleanup-all-buffers, where all remote connections and ad-hoc proxy definition are cleaned up.  However, additional buffers are killed only if one of the functions in tramp-cleanup-some-buffers-hook returns t.

 -- User Option: tramp-cleanup-some-buffers-hook
     The functions in this hook determine, whether a remote buffer is killed when tramp-cleanup-some-buffers is called.  Per default, remote buffers which are linked to a remote file, remote dired buffers, and buffers related to a remote process are cleaned up.

Renaming remote files
=====================

Sometimes, it is desirable to safe file contents of buffers visiting a given remote host.  This could happen for example, if the local host changes its network integration, and the remote host is not reachable anymore.

 -- Command: tramp-rename-files source target
     Replace in all buffers the visiting file name from SOURCE to TARGET.  SOURCE is a remote directory name, which can contain also a localname part.  TARGET is the directory name SOURCE is replaced with.  Often, TARGET is a remote directory name on another host, but it can also be a local directory name.  If TARGET has no local part, the local part from SOURCE is used.

     If TARGET is nil, it is selected according to the first match in tramp-default-rename-alist.  If called interactively, this match is offered as initial value for selection.

     On all buffers, which have a buffer-file-name matching SOURCE, this name is modified by replacing SOURCE with TARGET.  This is applied by calling set-visited-file-name.  The new buffer-file-name is prompted for modification in the minibuffer.  The buffers are marked modified, and must be saved explicitly.

     If user option tramp-confirm-rename-file-names is nil, changing the file name happens without confirmation.  This requires a matching entry in tramp-default-rename-alist.

     Remote buffers related to the remote connection identified by SOURCE, which are not visiting files, or which are visiting files not matching SOURCE, are not modified.

     Interactively, TARGET is selected from tramp-default-rename-alist without confirmation if the prefix argument is non-nil.

     The remote connection identified by SOURCE is flushed by tramp-cleanup-connection.

 -- Command: tramp-rename-these-files target
     Replace visiting file names to TARGET.  The current buffer must be related to a remote connection.  In all buffers, which are visiting a file with the same directory name, the buffer file name is changed.

     Interactively, TARGET is selected from tramp-default-rename-alist without confirmation if the prefix argument is non-nil.

 -- User Option: tramp-default-rename-alist
     The default target for renaming remote buffer file names.  This is an alist of cons cells (source . target).  The first matching item specifies the target to be applied for renaming buffer file names from source via tramp-rename-files.  source is a regular expression, which is used to match a remote file name.  target must be a directory name, which can be remote (including remote directories which tramp infers by default, such as method,user@host,).

     target can contain the format specifiers %m, %u, or %h, which are replaced by the method name, user name, or host name of source respectively when calling tramp-rename-files.

     source can also be a Lisp form, which is evaluated.  The result must be a string (which is used as a regular expression to match) or nil, which is interpreted as a regular expression which always matches.

     Example entries:

          ("ssh,badhost,/path/to/dir/"
           . "ssh,goodhost,/path/to/another/dir/")

     would trigger renaming of buffer file names on badhost to goodhost, including changing the directory name.

          ("ssh,.+\\\\.company\\\\.org,"
          . "prefixsshpostfixhopmulti.hop|
          sshpostfixhop%hpostfix")

     routes all connections to a host in company.org via ssh,multi.hop,, which might be useful when using Emacs outside the company network.

          (nil . "~/saved-files/%m:%u@%h/")

     saves all remote files locally, with a directory name including method name, user name and host name of the remote connection.

 -- User Option: tramp-confirm-rename-file-names
     Whether renaming a buffer file name by tramp-rename-files or tramp-rename-these-files must be confirmed.

Archive file names
==================

tramp offers also transparent access to files inside file archives.  This is possible only on hosts which have installed GVFS (the GNOME Virtual File System), see GVFS-based methods.  Internally, file archives are mounted via the GVFS archive method.

A file archive is a regular file of kind /path/to/dir/file.EXT. The extension .EXT identifies the type of the file archive.  To examine the contents of an archive with Dired, open file name as if it were a directory (i.e., open /path/to/dir/file.EXT/).  A file inside a file archive, called archive file name, has the name /path/to/dir/file.EXT/dir/file.

Most of the magic file name operations (elisp), are implemented for archive file names, exceptions are all operations which write into a file archive, and process related operations.  Therefore, functions like

     (copy-file "/path/to/dir/file.tar/dir/file" "/somewhere/else")

work out of the box.  This is also true for file name completion, and for libraries like dired or ediff, which accept archive file names as well.

File archives are identified by the file name extension .EXT. Since GVFS uses internally the library libarchive(3), all suffixes, which are accepted by this library, work also for archive file names.  Accepted suffixes are listed in the constant tramp-archive-suffixes.  They are

  * .7z --- 7-Zip archives

  * .apk --- Android package kits

  * .ar --- UNIX archiver formats

  * .cab, .CAB --- Microsoft Windows cabinets

  * .cpio --- CPIO archives

  * .crate --- Cargo (Rust) packages

  * .deb --- Debian packages

  * .depot --- HP-UX SD depots

  * .epub --- Electronic publications

  * .exe --- Self extracting Microsoft Windows EXE files

  * .iso --- ISO 9660 images

  * .jar --- Java archives

  * .lzh, .LZH --- Microsoft Windows compressed LHA archives

  * .msu, .MSU --- Microsoft Windows Update packages

  * .mtree --- BSD mtree format

  * .odb, .odf, .odg, .odp, .ods, .odt --- OpenDocument formats

  * .pax --- Posix archives

  * .rar --- RAR archives

  * .rpm --- Red Hat packages

  * .shar --- Shell archives

  * .tar, .tbz, .tgz, .tlz, .txz, .tzst --- (Compressed) tape archives

  * .warc --- Web archives

  * .xar --- macOS XAR archives

  * .xpi --- XPInstall Mozilla addons

  * .xps --- Open XML Paper Specification (OpenXPS) documents

  * .zip, .ZIP --- ZIP archives

File archives could also be compressed, identified by an additional compression suffix.  Valid compression suffixes are listed in the constant tramp-archive-compression-suffixes.  They are .bz2, .gz, .lrz, .lz, .lz4, .lzma, .lzo, .uu, .xz, .Z, and .zst.  A valid archive file name would be /path/to/dir/file.tar.gz/dir/file.  Even several suffixes in a row are possible, like /path/to/dir/file.tar.gz.uu/dir/file.

An archive file name can be a remote file name, as in /ftp:anonymous@ftp.gnu.org:/gnu/tramp/tramp-2.4.5.tar.gz/INSTALL. Since all file operations are mapped internally to GVFS operations, remote file names supported by tramp-gvfs perform better, because no local copy of the file archive must be downloaded first.  For example, /sftp:user@host:... performs better than the similar /scp:user@host:....  See the constant tramp-archive-all-gvfs-methods for a complete list of tramp-gvfs supported method names.

If url-handler-mode is enabled, archives can be visited via URLs, like https://ftp.gnu.org/gnu/tramp/tramp-2.4.5.tar.gz/INSTALL.  This allows complex file operations like

     (progn
       (url-handler-mode 1)
       (ediff-directories
        "https://ftp.gnu.org/gnu/tramp/tramp-2.4.4.tar.gz/tramp-2.4.4"
        "https://ftp.gnu.org/gnu/tramp/tramp-2.4.5.tar.gz/tramp-2.4.5" ""))

It is even possible to access file archives in file archives, as

     (progn
       (url-handler-mode 1)
       (find-file
        "https://ftp.debian.org/debian/pool/main/c/coreutils/\
     coreutils_8.28-1_amd64.deb/control.tar.gz/control"))

In order to disable file archives, you can add the following form to your init file:

     (customize-set-variable 'tramp-archive-enabled nil)

Reporting Bugs and Problems
***************************

tramp's development team is actively engaged in solving bugs and problems and looks to feature requests and suggestions.

tramp's mailing list is the place for more advice and information on working with tramp, solving problems, discussing, and general discussions about tramp.

tramp's mailing list is moderated but even non-subscribers can post for moderator approval.  Sometimes this approval step may take as long as 48 hours due to public holidays.

tramp-bug-report-address is the mailing list. Messages sent to this address go to all the subscribers.  This is not the address to send subscription requests to.

To subscribe to the mailing list, visit: the tramp Mail Subscription Page (https://lists.gnu.org/mailman/listinfo/tramp-devel/).

There is also a Gmane group, mirroring the mailing list. Its name is gmane.emacs.tramp.

Check if the bug or problem is already addressed in see Frequently Asked Questions.

Run M-x tramp-bug RET to generate a buffer with details of the system along with the details of the tramp installation. Please include these details with the bug report.

The bug report must describe in as excruciating detail as possible the steps required to reproduce the problem.  These details must include the setup of the remote host and any special or unique conditions that exist.

Include a minimal test case that reproduces the problem.  This will help the development team find the best solution and avoid unrelated detours.

To exclude cache-related problems, flush all caches before running the test, see Cleanup remote connections.  Alternatively, and often better for analysis, reproduce the problem in a clean Emacs session started with emacs -Q.  Then, tramp does not load the persistency file (see Connection caching), and it does not use passwords from auth-source.el (see Password handling).  The latter does not happen for the sudoedit method, otherwise it would be unusable.

If you use the GNU ELPA version of tramp, you must load it explicitly, because emacs -Q ignores installed ELPA packages.  Call (version number adapted)

     $ emacs -Q -l ~/.emacs.d/elpa/tramp-2.4.5.1/tramp-autoloads

When including tramp's messages in the bug report, increase the verbosity level to 6 (see Traces) in the ~/.emacs file before repeating steps to the bug.  Include the contents of the *tramp/foo* and *debug tramp/foo* buffers with the bug report.  Since those buffers could contain non-ASCII characters which are relevant for analysis, append the buffers as attachments to the bug report rather than placing them inline.  This is also needed in order to avoid line breaks getting added or deleted during mail transfer.

If you send the message from Emacs, you are asked whether to append these buffers to the bug report.  If you use an external mail program, you must save these buffers to files, and append them with that mail program.

Note that a verbosity level greater than 6 is not necessary at this stage.  Also note that with a verbosity level of 6 or greater, the contents of files and directories will be included in the debug buffer. Passwords typed in tramp will never be included there.

If you find, that using tramp with emacs -Q doesn't cause any problem, you might check your init file for the suspicious configuration by bisecting it.  That is, comment out about half of the init file, and check whether the problem still arises when calling emacs.  If yes, comment out half of the still active code. Otherwise, comment out the active code, and uncomment the just commented code.

Call emacs, again.  Reiterate, until you find the suspicious configuration.

Frequently Asked Questions
**************************

  * What is the official name - ``Tramp'' or ``tramp''?

     The official name is ``Tramp''.  This is used in comments, docstrings, and everywhere speaking about tramp.

     However, for historical reasons this is formatted as ``@sc{Tramp}'' in the tramp manual. see Smallcaps (texinfo). So it looks different there.

  * Where is the latest tramp?

     tramp is available at the GNU URL:

     https://ftp.gnu.org/gnu/tramp/

     tramp's GNU project page is located here:

     https://savannah.gnu.org/projects/tramp/

  * Which systems does it work on?

     The package works successfully on Emacs 27, Emacs 28, Emacs 29, and Emacs 30.

     While Unix and Unix-like systems are the primary remote targets, tramp has equal success connecting to other platforms, such as MS Windows 7/8/10.

  * How to speed up tramp?

     tramp does many things in the background, some of which depends on network speeds, response speeds of remote hosts, and authentication delays.  During these operations, tramp's responsiveness slows down.  Some suggestions within the scope of tramp's settings include:

       - Use an external method, such as scp, which are faster than internal methods for large files.

       - Keep the file tramp-persistency-file-name, which is where tramp caches remote information about hosts and files.  Caching is enabled by default.  Don't disable it.

          Set remote-file-name-inhibit-cache to nil if remote files are not independently updated outside tramp's control. That cache cleanup will be necessary if the remote directories or files are updated independent of tramp.

       - Disable version control to avoid delays:

               (setq vc-ignore-dir-regexp
                     (format "\\(%s\\)\\|\\(%s\\)"
                             vc-ignore-dir-regexp
                             tramp-file-name-regexp))

          If this is too radical, because you want to use version control remotely, trim vc-handled-backends to just those you care about, for example:

               (setq vc-handled-backends '(SVN Git))

       - Disable file locks.  Set remote-file-name-inhibit-locks to t if you know that different Emacs sessions are not modifying the same remote file.

       - Keep auto-save files local.  This is already the default configuration in Emacs, don't change it.  If you want to disable auto-saving for remote files at all, set remote-file-name-inhibit-auto-save to t, but think about the consequences!

          If you want to disable auto-saving just for selected connections, for example due to security considerations, use connection-local variables in order to set buffer-auto-save-file-name.  If you, for example, want to disable auto-saving for all sudo connections, apply the following code. See Connection Variables (emacs).

               (connection-local-set-profile-variables
                'my-auto-save-profile
                '((buffer-auto-save-file-name . nil)))

               (connection-local-set-profiles
                '(:application tramp :protocol "sudo")
                'my-auto-save-profile)

       - Use direct asynchronous processes if possible.

       - Suppress reading the remote history file in shell.  Set shell-history-file-name to t.

       - Disable excessive traces.  Set tramp-verbose to 3 or lower, default being 3.  Increase trace levels temporarily when hunting for bugs.

  * tramp does not connect to the remote host

     Three main reasons for why tramp does not connect to the remote host:

       - Unknown characters in the prompt

          tramp needs a clean recognizable prompt on the remote host for accurate parsing.  Shell prompts that contain escape sequences for coloring cause parsing problems.  Remote shell setup for customizing prompt detection using regular expressions.

          To check if the remote host's prompt is being recognized, use this test: switch to tramp connection buffer *tramp/foo*, put the cursor at the top of the buffer, and then apply the following expression:

               M-: (re-search-forward (concat tramp-shell-prompt-pattern "$")) RET

          If the cursor has not moved to the prompt at the bottom of the buffer, then tramp has failed to recognize the prompt.

          When using zsh on remote hosts, disable zsh line editor because zsh uses left-hand side and right-hand side prompts in parallel.  Add the following line to ~/.zshrc:

               [[ $TERM == "dumb" ]] && unsetopt zle && PS1='$ ' && return

          This uses the default value of tramp-terminal-type, "dumb", as value of the TERM environment variable.  If you want to use another value for TERM, change tramp-terminal-type and this line accordingly.

          Alternatively, you can set the remote login shell explicitly.  See Remote shell setup for discussion of this technique,

          When using fish shell on remote hosts, disable fancy formatting by adding the following to ~/.config/fish/config.fish:

               function fish_prompt
                 if test $TERM = "dumb"
                    echo "\$ "
                 else
                    ...
                 end
               end

          When using WinSSHD on remote hosts, tramp does not recognize the strange prompt settings.

          A similar problem exist with the iTerm2 shell integration, which sends proprietary escape codes when starting a shell.  This can be suppressed by changing the respective integration snippet in your ~/.profile like this:

               [ $TERM = "dumb" ] || \
               test -e "${HOME}/.iterm2_shell_integration.bash" && \
               source "${HOME}/.iterm2_shell_integration.bash"

          And finally, bash's readline should not use key bindings like C-j to commands.  Disable this in your ~/.inputrc:

               $if term=dumb
               # Don't bind Control-J or it messes up tramp.
               $else
               "\C-j": next-history
               $endif

       - Echoed characters after login

          tramp suppresses echos from remote hosts with the stty -echo command.  But sometimes it is too late to suppress welcome messages from the remote host containing harmful control characters.  Using sshx or scpx methods can avoid this problem because they allocate a pseudo tty.  See Inline methods.

       - tramp stops transferring strings longer than 500 characters

          Set tramp-chunksize to 500 to get around this problem, which is related to faulty implementation of process-send-string on HP-UX, FreeBSD and Tru64 Unix systems.  Consult the documentation for tramp-chunksize to see when this is necessary.

          Set file-precious-flag to t for files accessed by tramp so the file contents are checked using checksum by first saving to a temporary file. see Saving Buffers (elisp).

               (add-hook
                'find-file-hook
                (lambda ()
                  (when (file-remote-p default-directory)
                    (set (make-local-variable 'file-precious-flag) t))))

  * tramp fails in a chrooted environment

     When connecting to a local host, tramp uses some internal optimizations.  They fail when Emacs runs in a chrooted environment. In order to disable those optimizations, set user option tramp-local-host-regexp to nil.

  * tramp blocks Emacs at startup

     Some packages, like desktop.el or recentf.el, access remote files when loaded.  If the requested file is not accessible, tramp could block.  In order to check whether this could happen, add a test via access-file with a proper timeout prior to loading these packages:

          (let ((remote-file-name-access-timeout 10))
            (access-file "method,user@host,/path/to/file" "error"))
          => nil

     The result nil means success.  If the file is not accessible, or if the underlying operations last too long, access-file returns with an error.

     The value of the timeout (10 seconds in the example) depends on your preference and on the quality of the connection to the remote host. If the connection to the remote host isn't established yet, and if this requires an interactive password, the timeout check doesn't work properly.

     Note: In recent versions of Emacs, both packages already apply this check.  You just need to customize remote-file-name-access-timeout to the desired timeout (in seconds).

  * Does tramp support SSH security keys?

     Yes.  OpenSSH has added support for FIDO hardware devices via special key types *-sk.  tramp supports the additional handshaking messages for them.  This requires at least OpenSSH 8.2, and a FIDO U2F or FIDO2 compatible security key, like yubikey, solokey, nitrokey, or titankey.

     Note that there are reports on problems of handling FIDO2 (residential) keys by ssh-agent.  As workaround, you might disable ssh-agent for such keys.

  * Does tramp support fingerprint readers?

     Yes.  A fingerprint reader can be used as an additional authentication method for sudo-based logins.  tramp supports the required additional handshaking messages (It supports fingerprint readers driven by fprintd.).  If the fingerprint isn't recognized by the fingerprint reader in time, authentication falls back to requesting a password.

     If the user option tramp-use-fingerprint is nil, tramp interrupts the fingerprint request, falling back to password authentication immediately.

  * tramp does not connect to Samba or MS Windows hosts running SMB1 connection protocol

     Recent versions of smbclient do not support old connection protocols by default.  In order to connect to such a host, add a respective option:

          (add-to-list 'tramp-smb-options "client min protocol=NT1")

     Note that using a deprecated connection protocol raises security problems, you should do it only if absolutely necessary.

  * File name completion does not work with tramp

     ANSI escape sequences from the remote shell may cause errors in tramp's parsing of remote buffers.

     To test if this is the case, open a remote shell and check if the output of ls is in color.

     To disable ANSI escape sequences from the remote hosts, disable --color=yes or --color=auto in the remote host's .bashrc or .profile.  Turn this alias on and off to see if file name completion works.

  * File name completion does not work in directories with large number of files

     This may be related to globbing, which is the use of shell's ability to expand wild card specifications, such as *.c.  For directories with large number of files, globbing might exceed the shell's limit on length of command lines and hang.  tramp uses globbing.

     To test if globbing hangs, open a shell on the remote host and then run ls -d * ..?* > /dev/null.

     When testing, ensure the remote shell is the same shell (/bin/sh, ksh or bash), that tramp uses when connecting to that host.

  * How to get notified after tramp completes file transfers?

     Make Emacs beep after reading from or writing to the remote host with the following code in ~/.emacs.

          (add-hook 'tramp-handle-write-region-hook 'beep)
          (add-hook 'tramp-handle-file-local-copy-hook 'beep)

  * How to get a Visual Warning when working with root privileges? Host indication in the mode line?

     Install tramp-theme from GNU ELPA via Emacs's Package Manager. Enable it via M-x load-theme RET tramp RET.  Further customization is explained in user option tramp-theme-face-remapping-alist.

  * Remote host does not understand default options for directory listing

     Emacs computes the dired options based on the local host. Since Emacs 30, these options can be set connection-local. See Connection Variables (emacs).

          (connection-local-set-profile-variables
           'my-dired-profile
           '((dired-listing-switches . "-ahl")))

          (connection-local-set-profiles
           '(:application tramp :machine "remotehost")
           'my-dired-profile)

     In older Emacsen, you can set the dired options with a hook as follows:

          (add-hook
           'dired-before-readin-hook
           (lambda ()
             (when (string-equal
                     (file-remote-p default-directory 'host) "remotehost")
               (setq dired-actual-switches "-ahl"))))

  * tramp does not show directories or files although they are readable

     Internally, tramp uses commands like ls or stat in order to determine file permissions.  When NFS4_ACL is enabled on the remote host, more fine-grained information is used which cannot be reflected by the permission string returned from those commands.  Set the user option tramp-use-file-attributes to nil in such a case.  This can also be set host-wise, like in:

          (connection-local-set-profile-variables
           'my-file-attributes-profile
           '((tramp-use-file-attributes . nil)))

          (connection-local-set-profiles
           '(:application tramp :machine "remotehost")
           'my-file-attributes-profile)

  * Where are remote files trashed to?

     Emacs can trash files instead of deleting them, see Trashing (emacs). Remote files are always trashed to the local trash, except the user option remote-file-name-inhibit-delete-by-moving-to-trash is non-nil, or it is a remote encrypted file (see Keeping files encrypted), which are deleted anyway.

     If you want to trash a remote file into a remote trash directory, you can configure the user option trash-directory to a connection-local value. See Connection Variables (emacs).

          (connection-local-set-profile-variables
           'remote-trash-directory
           '((trash-directory . "/sudo::~/.local/share/Trash")))

          (connection-local-set-profiles
           `(:application tramp :protocol "sudo" :machine ,system-name)
           'remote-trash-directory)

     If Emacs is configured to use the XDG conventions for the trash directory, remote files cannot be restored with the respective tools, because those conventions don't specify remote paths.  Such files must be restored by moving them manually from ${XDG_DATA_HOME}/Trash/files/, if needed.

  * How to shorten long file names when typing in tramp?

     Adapt several of these approaches to reduce typing.  If the full name is ssh,news@news.my.domain,/opt/news/etc, then:

      1. Use simplified syntax:

          If you always apply the default method (see Default Method), you can use the simplified tramp syntax (see Change file name syntax):

               (customize-set-variable 'tramp-default-method "ssh")
               (tramp-change-syntax 'simplified)

          The reduced typing: C-x C-f
          prefixnews@news.my.domainpostfix/opt/news/etc
          RET.

      2. Use default values for method name and user name:

          You can define default methods and user names for hosts, (see Default Method, see Default User):

               (custom-set-variables
                '(tramp-default-method "ssh")
                '(tramp-default-user "news"))

          The reduced typing: C-x C-f -,news.my.domain,/opt/news/etc RET.

          Note that there are some useful shortcuts already.  Accessing your local host as root user, is possible just by C-x C-f su,, RET.

      3. Use configuration options of the access method:

          Programs used for access methods already offer powerful configurations (see Customizing Completion).  For ssh, configure the file ~/.ssh/config:

               Host xy
                    HostName news.my.domain
                    User news

          The reduced typing: C-x C-f ssh,xy,/opt/news/etc RET.

          Depending on the number of files in the directories, host names completion can further reduce key strokes: C-x C-f
          prefixsshpostfixhopx TAB.

      4. Use environment variables to expand long strings:

          For long file names, set up environment variables that are expanded in the minibuffer.  Environment variables are set either outside Emacs or inside Emacs with Lisp:

               (setenv "xy" "ssh,news@news.my.domain,/opt/news/etc/")

          The reduced typing: C-x C-f $xy RET.

          Note that file name cannot be edited here because the environment variables are not expanded during editing in the minibuffer.

      5. Define own keys:

          Redefine another key sequence in Emacs for C-x C-f:

               (global-set-key
                [(control x) (control y)]
                (lambda ()
                  (interactive)
                  (find-file
                   (read-file-name
                    "Find tramp file: "
                    "ssh,news@news.my.domain,/opt/news/etc/"))))

          Simply typing C-x C-y would prepare minibuffer editing of file name.

          See the Emacs Wiki (https://www.emacswiki.org/emacs/TrampMode) for a more comprehensive example.

      6. Define own abbreviation (1):

          Abbreviation list expansion can be used to reduce typing long file names:

               (add-to-list 'directory-abbrev-alist
                            '("^/xy" . "ssh,news@news.my.domain,/opt/news/etc/"))

          The reduced typing: C-x C-f /xy RET.

          Note that file name cannot be edited here because the abbreviations are not expanded during editing in the minibuffer. Furthermore, the abbreviation is not expanded during TAB completion.

      7. Define own abbreviation (2):

          The abbrev-mode gives additional flexibility for editing in the minibuffer:

               (define-abbrev-table 'my-tramp-abbrev-table
                 '(("xy" "ssh,news@news.my.domain,/opt/news/etc/")))

               (add-hook
                'minibuffer-setup-hook
                (lambda ()
                  (abbrev-mode 1)
                  (setq local-abbrev-table my-tramp-abbrev-table)))

               (advice-add 'minibuffer-complete
                :before 'expand-abbrev)

          The reduced typing: C-x C-f xy TAB.

          The minibuffer expands for further editing.

      8. Use bookmarks:

          Use bookmarks to save tramp file names. see Bookmarks (emacs).

          Upon visiting a location with tramp, save it as a bookmark with menu-bar edit bookmarks set.

          To revisit that bookmark: menu-bar edit bookmarks jump.

      9. Use recent files:

          recentf remembers visited places. see File Conveniences (emacs).

          Keep remote file names in the recent list without have to check for their accessibility through remote access:

               (recentf-mode 1)

          Reaching recently opened files: menu-bar file Open Recent.

      10. Use filecache:

          Since filecache remembers visited places, add the remote directory to the cache:

               (with-eval-after-load 'filecache
                 (file-cache-add-directory
                   "ssh,news@news.my.domain,/opt/news/etc/"))

          Then use directory completion in the minibuffer with C-x C-f C-TAB.

      11. Use bbdb:

          bbdb has a built-in feature for Ange FTP files, which also works for tramp file names. see Storing FTP sites in the BBDB (bbdb).

          Load bbdb in Emacs:

               (require 'bbdb)
               (bbdb-initialize)

          Create a BBDB entry with M-x bbdb-create-ftp-site RET. Then specify a method and user name where needed.  Examples:

               M-x bbdb-create-ftp-site RET
               Ftp Site: news.my.domain RET
               Ftp Directory: /opt/news/etc/ RET
               Ftp Username: sshpostfixhopnews RET
               Company: RET
               Additional Comments: RET

          In BBDB buffer, access an entry by pressing the key F.

     Thanks to tramp users for contributing to these recipes.

  * Why don't saved ad-hoc multi-hop file names work in a new Emacs session?

     By default, ad-hoc multi-hop file names are abbreviated after completing the initial connection.  These abbreviated forms retain only the final hop, and so only the Emacs session that generated the abbreviated form can understand it.  See Ad-hoc multi-hops.

     For example, after connecting to ssh,bird@bastion|
     sshpostfixhopnews@news.my.domain,/opt/news/etc, the file name becomes ssh,news@news.my.domain,/opt/news/etc. If the abbreviated form is saved in a bookmark, the recent files list, bbdb, or similar, a new Emacs session has no way to know that the connection must go through bird@bastion first.

     There are two mechanisms to deal with this.  The first is to customize tramp-show-ad-hoc-proxies to a non-nil value, which disables abbreviation.  Then the fully-qualified ad-hoc multi-hop file name is the one that will be both displayed and saved. See tramp-show-ad-hoc-proxies.

     Alternatively, you can customize tramp-save-ad-hoc-proxies to a non-nil value which means to save the information how an abbreviated multi-hop file name can be expanded. See tramp-save-ad-hoc-proxies.

  * How to connect to a remote Emacs session using tramp?

     Configure Emacs Client (see Emacs Server (emacs)).

     Then on the remote host, start the Emacs Server:

          (require 'server)
          (setq server-host (system-name)
                server-use-tcp t)
          (server-start)

     If (system-name) of the remote host cannot be resolved on the local host, use IP address instead.

     Copy from the remote host the resulting file ~/.emacs.d/server/server to the local host, to the same location.

     Then start Emacs Client from the command line:

          $ emacsclient ssh,user@host,/file/to/edit

     user and host refer to the local host.

     To make Emacs Client an editor for other programs, use a wrapper script emacsclient.sh:

          #!/bin/sh
          emacsclient ssh,$(whoami)@$(hostname --fqdn),$1

     Then change the environment variable EDITOR to point to the wrapper script:

          $ export EDITOR=/path/to/emacsclient.sh

  * How to determine whether a buffer is remote?

     The buffer-local variable default-directory tells this.  If the form (file-remote-p default-directory) returns non-nil, the buffer is remote.  See the optional arguments of file-remote-p for determining details of the remote connection.

  * How to save files when a remote host isn't reachable anymore?

     If the local machine Emacs is running on changes its network integration, remote hosts could become unreachable.  This happens, for example, if the local machine is moved between your office and your home without restarting Emacs.

     In such cases, the command tramp-rename-files can be used to alter remote buffers’ method, host, and/or directory names.  This permits saving their contents in the same location via another network path, or somewhere else entirely (including locally).  see Renaming remote files.

  * How to prevent tramp from clearing the recentf-list?

     When tramp cleans a connection, it removes the respective remote file name(s) from recentf-list.  This is needed, because an unresponsive remote host could trigger recentf to connect that host again and again.

     If you find the cleanup disturbing, because the file names in recentf-list are precious to you, you can add the following two forms in your ~/.emacs (after loading the tramp and recentf packages):

          (remove-hook
           'tramp-cleanup-connection-hook
           #'tramp-recentf-cleanup)

          (remove-hook
           'tramp-cleanup-all-connections-hook
           #'tramp-recentf-cleanup-all)

  * I get a warning Tramp has been compiled with Emacs a.b, this is Emacs c.d

  * I get an error tramp-file-name-handler: Invalid function: tramp-compat-with-mutex

     tramp comes with compatibility code for different Emacs versions.  When you see such a message (the text might differ), you don't use the Emacs built-in version of tramp, and you must recompile it.  In case you have installed tramp from GNU ELPA, see trampurl#ELPA-Installation.  Otherwise, see trampurl#Recompilation.

  * I get an error Remote file error: Forbidden reentrant call of Tramp

     Timers, process filters and sentinels, and other event based functions can run at any time, when a remote file operation is still running. This can cause tramp to block.  When such a situation is detected, this error is triggered.  It should be fixed in the respective function (sending an error report will help), but for the time being you can suppress this error by the following code in your ~/.emacs:

          (setq debug-ignored-errors
                (cons 'remote-file-error debug-ignored-errors))

  * I get an error Remote file error: Not a valid Tramp file name function `tramp-FOO-file-name-p'

     tramp has changed the signature of an internal function. External packages implementing an own tramp backend must follow this change.  Please report this problem to the author of that package.

     For the running session, tramp disables the external package, and you can continue to work.  If you don't want to see this error while activating tramp, you can suppress it by the same code as above in your ~/.emacs:

          (setq debug-ignored-errors
                (cons 'remote-file-error debug-ignored-errors))

  * I get an error unix_listener: path "/very/long/path/.cache/emacs/tramp.XXX" too long for Unix domain socket when connecting via ssh to a remote host.

     By default, tramp uses the directory ~/.cache/emacs/ for creation of OpenSSH Unix domain sockets.  On GNU/Linux, domain sockets have a much lower maximum path length (currently 107 characters) than normal files.

     You can change this directory by setting the user option small-temporary-file-directory to another name, like

          (unless small-temporary-file-directory
            (customize-set-variable
             'small-temporary-file-directory
             (format "/run/user/%d/emacs/" (user-uid)))
            (make-directory small-temporary-file-directory t))

     "/run/user/UID" is the value of the environment variable XDG_RUNTIME_DIR, which you can use instead via (getenv "XDG_RUNTIME_DIR").

  * How to ignore errors when changing file attributes?

     Sometimes, for example while saving remote files, errors appear when changing file attributes like permissions, time stamps, or ownership. If these errors can be ignored, set user option tramp-inhibit-errors-if-setting-file-attributes-fail to a non-nil value.  This transforms the error into a warning.

  * How to disable other packages from calling tramp?

     There are packages that call tramp without the user ever entering a remote file name.  Even without applying a remote file syntax, some packages enable tramp on their own.  How can users disable such features.

       - ido.el

          Disable tramp file name completion:

               (customize-set-variable 'ido-enable-tramp-completion nil)

       - rlogin.el

          Disable remote directory tracking mode:

               (rlogin-directory-tracking-mode -1)

  * How to disable tramp?

       - To keep Ange FTP as default the remote files access package, set this in .emacs:

               (customize-set-variable 'tramp-default-method "ftp")

          If you want to enable Ange FTP's syntax, add the following form:

               (tramp-change-syntax 'simplified)

       - To deactivate tramp for some look-alike remote file names, set tramp-ignored-file-name-regexp to a proper regexp in .emacs.  Note, that we don't use customize-set-variable, in order to avoid loading tramp.

               (setq tramp-ignored-file-name-regexp "\\`/ssh:example\\.com:")

          This is needed, if you mount for example a virtual file system on your local host's root directory as /ssh:example.com:.

       - To disable both tramp (and Ange FTP), type M-x
          inhibit-remote-files RET.  You can also add this to your .emacs.

               (inhibit-remote-files)

       - If you write code, which is intended to run only for local files, you can use the without-remote-files macro.

               (without-remote-files ...)

          This improves performance, because many primitive file name operations don't check any longer for tramp file name regexps then.

       - To unload tramp, type M-x tramp-unload-tramp RET. Unloading tramp resets Ange FTP plugins also.

  * What is the difference between Ange FTP and tramp?

     The difference is that Ange FTP uses ftp to transfer files between the local and the remote host, whereas tramp uses a combination of ssh and scp or other work-alike programs.

How file names, directories and localnames are mangled and managed
******************************************************************

Where temporary files are kept
==============================

Internally, tramp uses "~/.cache/emacs" as local temporary directory if it exists.  Otherwise, the value of temporary-file-directory is used, which is often "/tmp".

This local temporary directory is kept in the constant tramp-compat-temporary-file-directory.  In this manual, we use "<TMP>" for its value.

The temporary directory on a remote host is "/data/local/tmp" for the adb method, "/C$/Temp" for the smb method, and "/tmp" otherwise.  For some methods, this can be customized.

Temporary files have the file name prefix "tramp.".  If you want to change this prefix, for example because you want to identify temporary files produced by file-local-copy in your package, you can bind the variable tramp-temp-name-prefix temporarily:

     (let ((tramp-temp-name-prefix "my-prefix."))
       (file-local-copy "ssh,,.emacs"))
     => "/tmp/my-prefix.HDfgDZ"

Splitting a localname into its component parts
==============================================

tramp package redefines lisp functions file-name-directory and file-name-nondirectory to accommodate the unique file naming syntax that tramp requires.

The replacements dissect the file name, use the original handler for the localname, take that result, and then re-build the tramp file name.  By relying on the original handlers for localnames, tramp benefits from platform specific hacks to the original handlers.

Integrating with external Lisp packages
=======================================

In general, it is not recommended to use tramp functions and variables not described in this manual.  They might change their signature and/or semantics without any announcement.

File name completion
--------------------

Sometimes, it is not convenient to open a new connection to a remote host, including entering the password and alike.  For example, this is nasty for packages providing file name completion.  Such a package could signal to tramp, that they don't want it to establish a new connection.  Use the variable non-essential temporarily and bind it to non-nil value.

     (let ((non-essential t))
       ...)

File attributes cache
---------------------

Keeping a local cache of remote file attributes in sync with the remote host is a time-consuming operation.  Flushing and re-querying these attributes can tax tramp to a grinding halt on busy remote hosts.

To get around these types of slow-downs in tramp's responsiveness, set the process-file-side-effects to nil to stop tramp from flushing the cache.  This is helpful in situations where callers to process-file know there are no file attribute changes.  The let-bind form to accomplish this:

     (let (process-file-side-effects)
       ...)

For asynchronous processes, tramp uses a process sentinel to flush file attributes cache.  When callers to start-file-process know beforehand no file attribute changes are expected, then the process sentinel should be set to the default state.  In cases where the caller defines its own process sentinel, tramp's process sentinel is overwritten.  The caller can still flush the file attributes cache in its process sentinel with this code:

     (unless (memq (process-status proc) '(run open))
       (dired-uncache remote-directory))

Since tramp traverses subdirectories starting with the root directory, it is most likely sufficient to make the default-directory of the process buffer as the root directory.

Timers, process filters, process sentinels, redisplay
-----------------------------------------------------

Timers run asynchronously at any time when Emacs is waiting for sending a string to a process, or waiting for process output.  They can run any remote file operation, which would conflict with the already running remote file operation, if the same connection is affected.  tramp detects this situation, and raises the remote-file-error error.  A timer function should avoid this situation.  As a minimum, it should protect itself against this error, by wrapping the timer function body as follows:

     (ignore-error 'remote-file-error
       ...)

A similar problem could happen with process filters, process sentinels, and redisplay (updating the mode line).

Adding new methods to tramp
===========================

There are two ways to add new methods to tramp: writing a new backend including an own file name handler, or adding the new method, using the existing tramp-sh-file-name-handler.  The former shall happen inside the tramp repository, and it isn't discussed here.  The latter means usually a new ELPA package. see Customizing Methods for some examples.

Writing an own ELPA package
---------------------------

An external ELPA package foo-tramp.el, which intends to provide a new tramp method, say foo, must add this new method to the variable tramp-methods.  This variable is an alist with elements (NAME PARAM1 PARAM2 ...).

NAME is the method name, "foo" in this case. PARAMx is a pair of the form (KEY VALUE). See the docstring of variable tramp-methods for possible KEYs and VALUEs.  An example would be

     (add-to-list
      'tramp-methods
      `("foo"
        (tramp-login-program ,foo-tramp-executable)
        (tramp-login-args (("exec") ("%h") ("--") ("su - %u")))
        (tramp-remote-shell "/bin/sh")
        (tramp-remote-shell-args ("-i" "-c"))))

foo-tramp-executable in this example would be a Lisp constant, which is the program name of foo.

Another initialization could tell tramp which are the default user and host name for method foo.  This is done by calling tramp-set-completion-function:

     (tramp-set-completion-function
      "foo"
      '((tramp-foo--completion-function ARG)))

tramp-foo--completion-function is a function, which returns completion candidates.  ARG, a string, is the argument for the completion function, for example a file name to read from. see Customizing Completion for details.

Finally, it might also be helpful to define default user or host names for method foo, in case a remote file name leaves them empty. This can be performed by calling

     (add-to-list 'tramp-default-user-alist '("foo" nil "root"))
     (add-to-list 'tramp-default-host-alist '("foo" nil "localhost"))

see Default User and Default Host explaining the user options tramp-default-user-alist and tramp-default-host-alist.

Making a customized method optional
-----------------------------------

The settings of the previous subsection are global in the package foo-tramp.el, meaning they are activated when loading foo-tramp.  Sometimes, it is desired to make these settings available without loading the whole package foo-tramp, but declaring the new method foo as optional method only.  In this case, declare a function tramp-enable-foo-method which collects the initialization.  This function must be auto loaded.

     ;;;###autoload
     (defun tramp-enable-foo-method ()
       (add-to-list 'tramp-methods '("foo" ...))
       (tramp-set-completion-function "foo" ...)
       (add-to-list 'tramp-default-user-alist '("foo" ...))
       (add-to-list 'tramp-default-host-alist '("foo" ...)))

Then, you can activate method foo by calling M-x tramp-enable-method RET foo RET.  see Optional methods.

Activating a customized method without loading the package
----------------------------------------------------------

If you want to make method foo known after loading tramp, without loading the package foo-tramp.el, you must autoload the implementation of function tramp-enable-foo-method.  Add the following code in foo-tramp.el:

     ;;;###autoload
     (progn
       (defun tramp-enable-foo-method ()
         (add-to-list 'tramp-methods '("foo" ...))
         (tramp-set-completion-function "foo" ...)
         (add-to-list 'tramp-default-user-alist '("foo" ...))
         (add-to-list 'tramp-default-host-alist '("foo" ...))))

     ;;;###autoload
     (with-eval-after-load 'tramp (tramp-enable-method "foo"))

The trick is to wrap the function definition of tramp-enable-foo-method with progn for the ;;;###autoload cookie.

How to Customize Traces
***********************

tramp messages are raised with verbosity levels ranging from 0 to 10.  tramp does not display all messages; only those with a verbosity level less than or equal to tramp-verbose.

The verbosity levels are

   0  Silent (no tramp messages at all)

   1  Errors

   2  Warnings

   3  Connection to remote hosts (default verbosity)

   4  Activities

   5  Internal

   6  Sent and received strings

   7  Connection properties

   8  File caching

   9  Test commands

  10  Traces (huge)

  11  Call traces (maintainer only)

With tramp-verbose greater than or equal to 4, messages are also written to the tramp debug buffer *debug
tramp/foo*.  Such debug buffers are essential to bug and problem analyzes.  For tramp bug reports, set the tramp-verbose level to 6 (see Bug Reports).

The debug buffer is in Outline Mode (emacs). In this buffer, messages can be filtered by their level.  To see messages up to verbosity level 5, enter C-u 6 C-c C-q. Other navigation keys are described in Outline Visibility (emacs).

tramp handles errors internally.  Hence, to get a Lisp backtrace, the following settings are required:

     (setq debug-on-error t
           debug-on-signal t)

tramp warnings are displayed in the *Warnings* buffer, which pops up.  If you don't want to see this buffer for every tramp warning, set warning-suppress-types:

     (setq warning-suppress-types '((tramp)))

If tramp-verbose is greater than or equal to 10, Lisp backtraces are also added to the tramp debug buffer in case of errors.

In very rare cases it could happen, that tramp blocks Emacs. Killing Emacs does not allow inspecting the debug buffer.  In that case, you can instruct tramp to mirror the debug buffer to a file:

     (customize-set-variable 'tramp-debug-to-file t)

The debug buffer is written as a file in your Temporary directory.  Use this option with care, because it could decrease the performance of tramp actions.

If tramp-verbose is greater than or equal to 11, tramp function call traces are written to the buffer *trace tramp/foo*.

When tramp-debug-command-messages is non-nil, the debug buffer contains all messages with verbosity level 6 (sent and received strings), and the entry and exit messages for the function tramp-file-name-handler.  This is intended for tramp maintainers, analyzing the remote commands for performance analysis.

GNU Free Documentation License
******************************

     [file doclicense.texi not included]