Tramp User Manual

This file documents Tramp, a remote file editing package for Emacs.

Tramp stands for “Transparent Remote (file) Access, Multiple Protocol”. This package provides remote file editing, similar to Ange FTP.

The difference is that Ange FTP uses FTP to transfer files between the local and the remote host, whereas Tramp uses a combination of rsh and rcp or other work-alike programs, such as ssh/scp.

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

The latest release of Tramp is available for download, or you may see Obtaining Tramp for more details, including the Git server details.

Tramp also has a Savannah Project Page.

There is a mailing list for Tramp, available at, and archived at the Tramp Mail Archive.

Copyright © 1999–2018 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.”

Overview What Tramp can and cannot do.
For the end user:
Obtaining Tramp How to obtain Tramp.
History History of Tramp.
Quick Start Guide Short introduction how to use Tramp.
Configuration Configuring Tramp for use.
Usage An overview of the operation of Tramp.
Bug Reports Reporting Bugs and Problems.
Frequently Asked Questions Questions and answers from the mailing list.
For the developer:
Files directories and localnames How file names, directories and localnames are mangled and managed.
Traces and Profiles How to Customize Traces.
GNU Free Documentation License The license for this documentation.
Function Index Tramp functions.
Variable Index User options and variables.
Concept Index An item for each concept.

Detailed Node Listing

Configuring Tramp for use
Connection types Types of connections to remote hosts.
Inline methods Inline methods.
External methods External methods.
GVFS based methods GVFS based external methods.
Default Method Selecting a default method.
Default User Selecting a default user.
Default Host Selecting a default host.
Multi-hops Connecting to a remote host using multiple hops.
Firewalls Passing firewalls.
Customizing Methods Using Non-Standard Methods.
Customizing Completion Selecting config files for user/host name completion.
Password handling Reusing passwords for several connections.
Connection caching Reusing connection related information.
Predefined connection information Setting own connection related information.
Remote programs How Tramp finds and uses programs on the remote host.
Remote shell setup Remote shell setup hints.
Android shell setup Android shell setup hints.
Auto-save and Backup Auto-save and Backup.
Windows setup hints Issues with Cygwin ssh.
Using Tramp
File name syntax Tramp file name conventions.
Change file name syntax Alternative file name syntax.
File name completion File name completion.
Ad-hoc multi-hops Declaring multiple hops in the file name.
Remote processes Integration with other Emacs packages.
Cleanup remote connections Cleanup remote connections.
How file names, directories and localnames are mangled and managed
Localname deconstruction Breaking a localname into its components.
External packages Integration with external Lisp packages.

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1 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 rsh, rlogin, 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 connection to that host, here's what happens:

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

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2 Obtaining Tramp

Tramp is included as part of Emacs (since Emacs 22.1).

Tramp is also freely packaged for download on the Internet at

Tramp development versions are available on Git servers. Development versions contain new and incomplete features.

One way to obtain from 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.

Another way is to follow the terminal session below:

     $ cd ~/emacs
     $ git clone git://

From behind a firewall:

     $ git config --global http.proxy
     $ git clone

Tramp developers:

     $ git clone

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

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3 History of Tramp

Tramp development started at the end of November 1998 as rssh.el. It provided only one method of access. It used ssh for login and scp to transfer file contents. The name was changed to rcp.el before it got its present name Tramp. New methods of remote access were added, so was support for version control.

April 2000 was the first time when multi-hop methods were added. In July 2002, Tramp unified file names with Ange FTP. In July 2004, proxy hosts replaced multi-hop methods. Running commands on remote hosts was introduced in December 2005. Support for gateways since April 2007 (and removed in December 2016). GVFS integration started in February 2009. Remote commands on MS Windows hosts since September 2011. Ad-hoc multi-hop methods (with a changed syntax) re-enabled in November 2011. In November 2012, added Juergen Hoetzel's tramp-adb.el.

XEmacs support was stopped in January 2016. Since March 2017, Tramp syntax mandates a method.

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4 Short introduction how to use Tramp

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

You can use remote files exactly like ordinary files, that means you could 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 run even processes on a remote host, when the buffer you call the process from has a remote default-directory.

4.1 File name syntax

Remote file names are prepended by the method, user and host parts. 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 /-::, therefore. The ‘-’ notation for the default host is used for syntactical reasons, Default Host.

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 this case it is written as user%domain.

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

4.2 Using ssh and plink

If your local host runs an SSH client, and the remote host runs an SSH server, the most simple 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 taken often for testing Tramp.

On MS Windows, PuTTY is often used as 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.

sudo and sg methods

4.3 Using su, sudo and sg

Sometimes, it is necessary to work on your local host under different permissions. For this, you could use the su or sudo connection method. Both 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”; the changed group must be used here as user name. The default host name is the same.

4.4 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.

4.5 Using GVFS-based methods

On systems, which have installed the virtual file system for the Gnome Desktop (GVFS), its offered methods could 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 and /davs:user@host:/path/to/file (for WebDAV shares).

4.6 Using Google Drive

Another GVFS-based method allows to access a Google Drive file system. The file name syntax is here always / ‘’ stands here for your Google Drive account.

4.7 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.

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5 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 is installed and loaded:

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

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5.1 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 such a way that they don't require a password (with ssh-agent, or such alike). Modern scp implementations offer options to reuse existing ssh connections, which will be enabled by default if available. If it isn't possible, you should consider Password handling, otherwise you will be prompted for a password every copy action.

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5.2 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 mimencode (part of the metamail package) or uuencode. Tramp uses the first reliable command it finds. Tramp's search path can be customized, see Remote programs.

In case both mimencode and uuencode are unavailable, Tramp first transfers a small Perl program to the remote host, and then tries that program for encoding and decoding.

To increase transfer speeds for large text files, use compression before encoding. The user option tramp-inline-compress-start-size specifies the file size for such optimization.

rsh is an option for connecting to hosts within local networks since rsh is not as secure as other methods.
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.

Connecting to a remote host with telnet is as insecure as the rsh method.
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.
Similar to su method, sudo uses sudo. sudo must have sufficient rights to start a shell.
This method is used on OpenBSD like the sudo command.
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.
Works like ssh but without the extra authentication prompts. sshx uses ‘ssh -t -t host -l user /bin/sh’ to open a connection with a “standard” login shell.

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.

This method is also similar to ssh. It uses the krlogin -x command only for remote host login.
This is another method from the Kerberos suite. It behaves like su.
plink method is for MS Windows users with the PuTTY implementation of SSH. It uses ‘plink -ssh’ to log in to the remote host.

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

plink method supports the ‘-P’ argument.

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.

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

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5.3 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.

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.

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.

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.

This method supports the ‘-p’ argument.

scpx is useful to avoid login shell questions. It is similar in performance to scp. scpx uses ‘ssh -t -t host -l user /bin/sh’ to open a connection.

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.

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.

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

These methods support the ‘-P’ argument.

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.

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.
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.
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:


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:


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:


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

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 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.

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5.4 GVFS based external methods

GVFS is the virtual file system for the Gnome Desktop, 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. Emacs must have the message bus system, D-Bus integration active, see D-Bus.

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 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.
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 / 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.

OBEX is an FTP-like access protocol for cell phones and similar simple devices. Tramp supports OBEX over Bluetooth.
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.
synce method allows connecting to MS Windows Mobile devices. It uses GVFS for mounting remote files and directories via FUSE and requires the SYNCE-GVFS plugin.
— 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, obex, sftp and synce. Other methods to include are: ftp and smb.

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5.5 Selecting a default method

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

5.5.1 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.

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. 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.

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5.6 Selecting a default user

— User Option: tramp-default-user

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)

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5.7 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:

           '(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 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.

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5.8 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

proxy can take patterns %h or %u for host or user respectively.

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.

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

Next: , Previous: Multi-hops, Up: Configuration

5.9 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 ssh 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.

5.9.1 Tunneling with ssh

With ssh, you could use the ProxyCommand entry in the ~/.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.

5.9.2 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.

Next: , Previous: Firewalls, Up: Configuration

5.10 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>.

Next: , Previous: Customizing Methods, Up: Configuration

5.11 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.


          (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.


          (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:

This function parses files which are syntactical equivalent to ~/.rhosts. It returns both host names and user names, if specified.
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.
This function returns the host nicknames defined by Host entries in ~/.ssh/config style files.
SSH2 parsing of directories /etc/ssh2/hostkeys/* and ~/ssh2/hostkeys/*. Hosts are coded in file names User names are always nil.
Another SSH2 style parsing of directories like /etc/ssh2/knownhosts/* and ~/ssh2/knownhosts/*. This case, hosts names are coded in file names User names are always nil.
A function dedicated to /etc/hosts for host names.
A function which parses /etc/passwd files for user names.
A function which parses /etc/group files for group names.
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.


          (my-tramp-parse "~/.my-tramp-hosts")
               ⇒ ((nil "toto") ("daniel" "melancholia"))

Next: , Previous: Customizing Completion, Up: Configuration

5.12 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.

5.12.1 Using an authentication file

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

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

5.12.2 Caching passwords

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

password-cache-expiry sets the duration (in seconds) the passwords are remembered. Passwords are never saved permanently nor can they extend beyond the lifetime of the current Emacs session. Set password-cache-expiry to nil to disable expiration.

Set password-cache to nil to disable password caching.

Next: , Previous: Password handling, Up: Configuration

5.13 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.

Next: , Previous: Connection caching, Up: Configuration

5.14 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 could also be any property found in tramp-persistency-file-name.

To get around how restricted shells randomly drop connections, set the special property ‘busybox’. For example:

     (add-to-list 'tramp-connection-properties
                  (list (regexp-quote "/ssh:user@randomhost.your.domain:")
                        "busybox" t))

Next: , Previous: Predefined connection information, Up: Configuration

5.15 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/SUNWspro/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’.

When remote search paths are changed, local Tramp caches must be recomputed. To force Tramp to recompute afresh, exit Emacs, remove the persistent file (see Connection caching), and restart Emacs.

Next: , Previous: Remote programs, Up: Configuration

5.16 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 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 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:
              '("passphrase" "Passphrase"
                ;; English
                "password" "Password"
                ;; Deutsch
                "passwort" "Passwort"
                ;; Fran├žais
                "mot de passe" "Mot de passe")
             ".*:\0? *"))

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

tset and other questions
To suppress inappropriate prompts for terminal type, Tramp sets the TERM to dumb before the remote login process begins via the user option tramp-terminal-type. 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
            (concat (regexp-opt '("Enter the birth date of your mother:") t)
            "Regular expression matching my login prompt question.")
          (defun my-tramp-action (proc vec)
            "Enter \"19000101\" in order to give a correct answer."
              (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))

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 Tramp variables.

Tramp sets the INSIDE_EMACS 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 [ "${INSIDE_EMACS/*tramp*/tramp}" == "tramp" ] ; then
             PS1="[\u@\h \w]$ "

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:

           `(,(regexp-quote "")
             "remote-copy-args" (("-l") ("%r"))))

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

Next: , Previous: Remote shell setup, Up: Configuration

5.17 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 filesystem via dired.

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

Next: , Previous: Android shell setup, Up: Configuration

5.18 Auto-save 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 Tramp 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)
                   (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.


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

The backup file name of /su:root@localhost:/etc/secretfile would be /su:root@localhost:~/.emacs.d/backups/!su:root@localhost:!etc!secretfile~

Just as for backup files, similar issues of file naming affect auto-saving Tramp 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.

Previous: Auto-save and Backup, Up: Configuration

5.19 Issues with Cygwin ssh

This section is incomplete. Please share your solutions.

Cygwin's ssh works only with a Cygwin version of Emacs. To check for compatibility: type M-x eshell <RET>, and start ssh <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 for details.

On the Emacs Wiki 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 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 Pageant. It is part of the Putty Suite of tools.

The fallback is to start Emacs from a shell.

Next: , Previous: Configuration, Up: Top

6 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.

Next: , Up: Usage

6.1 Tramp file name conventions

/method:host:/path/to/file opens file /path/to/file on the remote host host, using the method method.

For the file .emacs located in the home directory, on the host melancholia, using method ssh.
For the file .emacs specified using the fully qualified domain name of the host.
For the file .emacs specified using the ~, which is expanded.
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.
For the file /etc/squid.conf on the host melancholia.

host can take IPv4 or IPv6 address, as in /ssh: or /ssh:[::1]:.emacs. For syntactical reasons, IPv6 addresses must be embedded in square brackets [ and ].

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:


/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. For syntactical reasons, the default method must be indicated by the pseudo method -.

Next: , Previous: File name syntax, Up: Usage

6.2 Alternative file name syntax

The syntax described in File name syntax is the default syntax, which is active after Emacs startup. However, this can be changed.

— Command: tramp-change-syntax syntax

This command changes the syntax Tramp uses for remote file names. Beside the default value, syntax can be

  • simplified The remote file name syntax is similar to the syntax used by Ange FTP. A remote file name has the form /user@host:path/to/file. The user@ part is optional, and the method is determined by Default Method.
  • separate

    The remote file name syntax is similar to the syntax used by XEmacs. A remote file name has the form /[method/user@host]path/to/file. The method and user@ parts are optional.

— Variable: tramp-file-name-regexp

This variable keeps a regexp which matches the selected remote file name syntax. However, it is not recommended to use this variable in external packages, a call of file-remote-p is much more appropriate.

Next: , Previous: Change file name syntax, Up: Usage

6.3 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. Enable this by activating partial completion in .emacs.

For example, type C-x C-f / s <TAB>, Tramp completion choices show up as


sbin/ scp: scpx: sftp: sg:
smb: srv/ ssh: sshx: su:
sudo: sys/

ssh:’ is a possible completion for the respective method, and ‘sbin/’ stands for the directory /sbin on your local host.

Type s h : for the minibuffer completion to ‘/ssh:’. Typing <TAB> shows host names Tramp extracts from ~/.ssh/config file, for example.


ssh: ssh:
ssh:[::1]: ssh:localhost: ssh:melancholia:

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.

Remote hosts previously visited or hosts whose connections are kept persistently (see Connection caching) will be included in the completion lists.

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.


     C-x C-f /ssh:melancholia:/usr/local/bin//etc <TAB>
          -| /ssh:melancholia:/etc
     C-x C-f /ssh:melancholia://etc <TAB>
          -| /etc
     C-x C-f /ssh:melancholia:/usr/local/bin///etc <TAB>
          -| /etc

During file name completion, remote directory contents are re-read regularly to account for any changes in the filesystem that may affect the completion candidates. Such re-reads can account for changes to the file system by applications outside Emacs (see Connection caching).

— User Option: tramp-completion-reread-directory-timeout

The timeout is number of seconds since last remote command for rereading remote directory contents. A value of 0 re-reads immediately during file name completion, nil uses cached directory contents.

Next: , Previous: File name completion, Up: Usage

6.4 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 /ssh:bird@bastion|ssh:you@remotehost:/path <RET>

Proxies can take patterns %h or %u.

Tramp adds the ad-hoc definitions on the fly to tramp-default-proxies-alist and is available for re-use during that Emacs session. Subsequent Tramp connections to the same remote host can then use the shortcut form: ‘/ssh:you@remotehost:/path’.

— 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.

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

Next: , Previous: Ad-hoc multi-hops, Up: Usage

6.5 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 "/"))
       (start-file-process "grep" (get-buffer-create "*grep*")
                           "/bin/sh" "-c" "grep -e tramp *"))

Remote processes do not apply to GVFS (see GVFS based methods) because the remote file system is mounted on the local host and Tramp just accesses 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: compile.el (commands like compile and grep) and gud.el (gdb or perldb).

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. Per default, Tramp has disabled this. You could overwrite 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.

6.5.1 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 the file ~/.ssh/config on the local host.

6.5.2 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.

Starting with Emacs 26, you could use connection-local variables for setting different values of explicit-shell-file-name for different remote hosts.

       '((explicit-shell-file-name . "/bin/bash")
         (explicit-bash-args . ("-i"))))
       '((explicit-shell-file-name . "/bin/ksh")
         (explicit-ksh-args . ("-i"))))
       '(:application tramp :protocol "ssh" :machine "localhost")
       `(:application tramp :protocol "sudo"
         :user "root" :machine ,(system-name))

6.5.3 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, *Async Shell Command*

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

6.5.4 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 em-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>
     /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 $

6.5.5 Running a debugger on a remote host

gud.el provides a unified interface to symbolic debuggers 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 exists in /ssh:host:/home/user, valid calls include:

     M-x perldb <RET>
     Run perldb (like this): perl -d <RET>

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

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

6.5.6 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" "-"))

Previous: Remote processes, Up: Usage

6.6 Cleanup remote connections

Tramp provides several ways to flush remote connections.

— Command: tramp-cleanup-connection vec

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 connection buffers.

— Command: tramp-cleanup-this-connection

Flushes only 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.

— Command: tramp-cleanup-all-buffers

Just as for tramp-cleanup-all-connections, all remote connections are cleaned up in addition to killing buffers related to that remote connection.

Next: , Previous: Usage, Up: Top

7 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. 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.

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, Cleanup remote connections.

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.

Note that a verbosity level greater than 6 is not necessary at this stage. Also note that 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.

Next: , Previous: Bug Reports, Up: Top

8 Frequently Asked Questions

Next: , Previous: Frequently Asked Questions, Up: Top

9 How file names, directories and localnames are mangled and managed.

Next: , Up: Files directories and localnames

9.1 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.

Previous: Localname deconstruction, Up: Files directories and localnames

9.2 Integrating with external Lisp packages

9.2.1 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))

9.2.2 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 servers.

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.

Next: , Previous: Files directories and localnames, Up: Top

10 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 file caching
 8 connection properties
 9 test commands
10 traces (huge)

With tramp-verbose greater than or equal to 4, messages are also written to a Tramp debug buffer. Such debug buffers are essential to bug and problem analyses. For Tramp bug reports, set the tramp-verbose level to 6 (see Bug Reports).

The debug buffer is in Outline Mode. 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.

Tramp handles errors internally. But to get a Lisp backtrace, both the error and the signal have to be set as follows:

     (setq debug-on-error t
           debug-on-signal t)

If tramp-verbose is greater than or equal to 10, Lisp backtraces are also added to the Tramp debug buffer in case of errors.

To enable stepping through Tramp function call traces, they have to be specifically enabled as shown in this code:

     (require 'trace)
     (dolist (elt (all-completions "tramp-" obarray 'functionp))
       (trace-function-background (intern elt)))
     (untrace-function 'tramp-read-passwd)

The buffer *trace-output* contains the output from the function call traces. Disable tramp-read-passwd to stop password strings from being written to *trace-output*.

Next: , Previous: Traces and Profiles, Up: Top

Appendix A GNU Free Documentation License

Version 1.3, 3 November 2008
     Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

    The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.


    This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

    A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

    A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

    The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

    The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

    A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

    Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

    The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

    The “publisher” means any person or entity that distributes copies of the Document to the public.

    A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

    The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.


    You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

    You may also lend copies, under the same conditions stated above, and you may publicly display copies.


    If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

    If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

    If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

    It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.


    You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

    1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
    2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
    3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
    4. Preserve all the copyright notices of the Document.
    5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
    6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
    7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
    8. Include an unaltered copy of this License.
    9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
    10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
    11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
    12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
    13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
    14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
    15. Preserve any Warranty Disclaimers.

    If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

    You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

    You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

    The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.


    You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

    The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

    In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”


    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

    You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.


    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.


    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

    If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.


    You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

    However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

    Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

    Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.


    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Document.


    “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

    “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

    “Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

    An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

       Copyright (C)  year  your name.
       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, no Front-Cover Texts, and no Back-Cover
       Texts.  A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this:

         with the Invariant Sections being list their titles, with
         the Front-Cover Texts being list, and with the Back-Cover Texts
         being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.

Next: , Previous: GNU Free Documentation License, Up: Top

Function Index

Next: , Previous: Function Index, Up: Top

Variable Index

Previous: Variable Index, Up: Top

Concept Index