ssh_config.0

OpenSSL Source code for SFTP, SSH, and many others

SSH_CONFIG(5)             System File Formats Manual             SSH_CONFIG(5)

NAME
     ssh_config - OpenSSH SSH client configuration files

SYNOPSIS
     $HOME/.ssh/config
     /etc/ssh/ssh_config

DESCRIPTION
     ssh obtains configuration data from the following sources in the followM--
     ing order: command line options, user's configuration file
     ($HOME/.ssh/config), and system-wide configuration file
     (/etc/ssh/ssh_config).

     For each parameter, the first obtained value will be used.  The configuM--
     ration files contain sections bracketed by ``Host'' specifications, and
     that section is only applied for hosts that match one of the patterns
     given in the specification.  The matched host name is the one given on
     the command line.

     Since the first obtained value for each parameter is used, more host-speM--
     cific declarations should be given near the beginning of the file, and
     general defaults at the end.

     The configuration file has the following format:

     Empty lines and lines starting with `#' are comments.

     Otherwise a line is of the format ``keyword arguments''.  Configuration
     options may be separated by whitespace or optional whitespace and exactly
     one `='; the latter format is useful to avoid the need to quote whitesM--
     pace when specifying configuration options using the ssh, scp and sftp -o
     option.

     The possible keywords and their meanings are as follows (note that keyM--
     words are case-insensitive and arguments are case-sensitive):

     Host    Restricts the following declarations (up to the next Host keyM--
             word) to be only for those hosts that match one of the patterns
             given after the keyword.  `*' and `'?  can be used as wildcards
             in the patterns.  A single `*' as a pattern can be used to proM--
             vide global defaults for all hosts.  The host is the hostname
             argument given on the command line (i.e., the name is not conM--
             verted to a canonicalized host name before matching).

     AFSTokenPassing
             Specifies whether to pass AFS tokens to remote host.  The arguM--
             ment to this keyword must be ``yes'' or ``no''.  This option
             applies to protocol version 1 only.

     BatchMode
             If set to ``yes'', passphrase/password querying will be disabled.
             This option is useful in scripts and other batch jobs where no
             user is present to supply the password.  The argument must be
             ``yes'' or ``no''.  The default is ``no''.

     BindAddress
             Specify the interface to transmit from on machines with multiple
             interfaces or aliased addresses.  Note that this option does not
             work if UsePrivilegedPort is set to ``yes''.

     ChallengeResponseAuthentication
             Specifies whether to use challenge response authentication.  The
             argument to this keyword must be ``yes'' or ``no''.  The default
             is ``yes''.

     CheckHostIP
             If this flag is set to ``yes'', ssh will additionally check the
             host IP address in the known_hosts file.  This allows ssh to
             detect if a host key changed due to DNS spoofing.  If the option
             is set to ``no'', the check will not be executed.  The default is
             ``yes''.

     Cipher  Specifies the cipher to use for encrypting the session in protoM--
             col version 1.  Currently, ``blowfish'', ``3des'', and ``des''
             are supported.  des is only supported in the ssh client for
             interoperability with legacy protocol 1 implementations that do
             not support the 3des cipher.  Its use is strongly discouraged due
             to cryptographic weaknesses.  The default is ``3des''.

     Ciphers
             Specifies the ciphers allowed for protocol version 2 in order of
             preference.  Multiple ciphers must be comma-separated.  The
             default is

               ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
                 aes192-cbc,aes256-cbc''

     ClearAllForwardings
             Specifies that all local, remote and dynamic port forwardings
             specified in the configuration files or on the command line be
             cleared.  This option is primarily useful when used from the ssh
             command line to clear port forwardings set in configuration
             files, and is automatically set by scp(1) and sftp(1).  The arguM--
             ment must be ``yes'' or ``no''.  The default is ``no''.

     Compression
             Specifies whether to use compression.  The argument must be
             ``yes'' or ``no''.  The default is ``no''.

     CompressionLevel
             Specifies the compression level to use if compression is enabled.
             The argument must be an integer from 1 (fast) to 9 (slow, best).
             The default level is 6, which is good for most applications.  The
             meaning of the values is the same as in gzip(1).  Note that this
             option applies to protocol version 1 only.

     ConnectionAttempts
             Specifies the number of tries (one per second) to make before
             exiting.  The argument must be an integer.  This may be useful in
             scripts if the connection sometimes fails.  The default is 1.

     DynamicForward
             Specifies that a TCP/IP port on the local machine be forwarded
             over the secure channel, and the application protocol is then
             used to determine where to connect to from the remote machine.
             The argument must be a port number.  Currently the SOCKS4 protoM--
             col is supported, and ssh will act as a SOCKS4 server.  Multiple
             forwardings may be specified, and additional forwardings can be
             given on the command line.  Only the superuser can forward priviM--
             leged ports.

     EscapeChar
             Sets the escape character (default: `~').  The escape character
             can also be set on the command line.  The argument should be a
             single character, `^' followed by a letter, or ``none'' to disM--
             able the escape character entirely (making the connection transM--
             parent for binary data).

     ForwardAgent
             Specifies whether the connection to the authentication agent (if
             any) will be forwarded to the remote machine.  The argument must
             be ``yes'' or ``no''.  The default is ``no''.

     ForwardX11
             Specifies whether X11 connections will be automatically rediM--
             rected over the secure channel and DISPLAY set.  The argument
             must be ``yes'' or ``no''.  The default is ``no''.

     GatewayPorts
             Specifies whether remote hosts are allowed to connect to local
             forwarded ports.  By default, ssh binds local port forwardings to
             the loopback address.  This prevents other remote hosts from conM--
             necting to forwarded ports.  GatewayPorts can be used to specify
             that ssh should bind local port forwardings to the wildcard
             address, thus allowing remote hosts to connect to forwarded
             ports.  The argument must be ``yes'' or ``no''.  The default is
             ``no''.

     GlobalKnownHostsFile
             Specifies a file to use for the global host key database instead
             of /etc/ssh/ssh_known_hosts.

     HostbasedAuthentication
             Specifies whether to try rhosts based authentication with public
             key authentication.  The argument must be ``yes'' or ``no''.  The
             default is ``no''.  This option applies to protocol version 2
             only and is similar to RhostsRSAAuthentication.

     HostKeyAlgorithms
             Specifies the protocol version 2 host key algorithms that the
             client wants to use in order of preference.  The default for this
             option is: ``ssh-rsa,ssh-dss''.

     HostKeyAlias
             Specifies an alias that should be used instead of the real host
             name when looking up or saving the host key in the host key
             database files.  This option is useful for tunneling ssh connecM--
             tions or for multiple servers running on a single host.

     HostName
             Specifies the real host name to log into.  This can be used to
             specify nicknames or abbreviations for hosts.  Default is the
             name given on the command line.  Numeric IP addresses are also
             permitted (both on the command line and in HostName specificaM--
             tions).

     IdentityFile
             Specifies a file from which the user's RSA or DSA authentication
             identity is read. The default is $HOME/.ssh/identity for protocol
             version 1, and $HOME/.ssh/id_rsa and $HOME/.ssh/id_dsa for protoM--
             col version 2.  Additionally, any identities represented by the
             authentication agent will be used for authentication.  The file
             name may use the tilde syntax to refer to a user's home direcM--
             tory.  It is possible to have multiple identity files specified
             in configuration files; all these identities will be tried in
             sequence.

     KeepAlive
             Specifies whether the system should send TCP keepalive messages
             to the other side.  If they are sent, death of the connection or
             crash of one of the machines will be properly noticed.  However,
             this means that connections will die if the route is down temM--