path: root/ssh_config.0

SSH_CONFIG(5)               BSD File Formats Manual              SSH_CONFIG(5)

^[[1mNAME^[[0m
     ^[[1mssh_config ^[[22mM-bMM-^R OpenSSH SSH client configuration files

^[[1mSYNOPSIS^[[0m
     ^[[4m$HOME/.ssh/config^[[0m
     ^[[4m/etc/ssh/ssh_config^[[0m

^[[1mDESCRIPTION^[[0m
     ^[[1mssh ^[[22mobtains configuration data from the following sources in the followM-bM-^@M-^P
     ing order:
           1.   commandM-bM-^@M-^Pline options
           2.   userM-bM-^@M-^Ys configuration file (^[[4m$HOME/.ssh/config^[[24m)
           3.   systemM-bM-^@M-^Pwide configuration file (^[[4m/etc/ssh/ssh_config^[[24m)

     For each parameter, the first obtained value will be used.  The configuM-bM-^@M-^P
     ration files contain sections bracketed by M-bM-^@M-^\HostM-bM-^@M-^] 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 hostM-bM-^@M-^PspeM-bM-^@M-^P
     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 M-bM-^@M-^X#M-bM-^@M-^Y are comments.

     Otherwise a line is of the format M-bM-^@M-^\keyword argumentsM-bM-^@M-^].  Configuration
     options may be separated by whitespace or optional whitespace and exactly
     one M-bM-^@M-^X=M-bM-^@M-^Y; the latter format is useful to avoid the need to quote whitesM-bM-^@M-^P
     pace when specifying configuration options using the ^[[1mssh^[[22m, ^[[1mscp ^[[22mand ^[[1msftp M-bMM-^Ro^[[0m
     option.

     The possible keywords and their meanings are as follows (note that keyM-bM-^@M-^P
     words are caseM-bM-^@M-^Pinsensitive and arguments are caseM-bM-^@M-^Psensitive):

     ^[[1mHost    ^[[22mRestricts the following declarations (up to the next ^[[1mHost ^[[22mkeyM-bM-^@M-^P
             word) to be only for those hosts that match one of the patterns
             given after the keyword.  M-bM-^@M-^X*M-bM-^@M-^Y and M-bM-^@M-^XM-bM-^@M-^Y?  can be used as wildcards
             in the patterns.  A single M-bM-^@M-^X*M-bM-^@M-^Y as a pattern can be used to proM-bM-^@M-^P
             vide global defaults for all hosts.  The host is the ^[[4mhostname^[[0m
             argument given on the command line (i.e., the name is not conM-bM-^@M-^P
             verted to a canonicalized host name before matching).

     ^[[1mAFSTokenPassing^[[0m
             Specifies whether to pass AFS tokens to remote host.  The arguM-bM-^@M-^P
             ment to this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  This option applies
             to protocol version 1 only.

     ^[[1mBatchMode^[[0m
             If set to M-bM-^@M-^\yesM-bM-^@M-^], 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
             M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The default is M-bM-^@M-^\noM-bM-^@M-^].

     ^[[1mBindAddress^[[0m
             Specify the interface to transmit from on machines with multiple
             interfaces or aliased addresses.  Note that this option does not
             work if ^[[1mUsePrivilegedPort ^[[22mis set to M-bM-^@M-^\yesM-bM-^@M-^].

     ^[[1mChallengeResponseAuthentication^[[0m
             Specifies whether to use challenge response authentication.  The
             argument to this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The default is
             M-bM-^@M-^\yesM-bM-^@M-^].

     ^[[1mCheckHostIP^[[0m
             If this flag is set to M-bM-^@M-^\yesM-bM-^@M-^], ssh will additionally check the
             host IP address in the ^[[4mknown_hosts^[[24m file.  This allows ssh to
             detect if a host key changed due to DNS spoofing.  If the option
             is set to M-bM-^@M-^\noM-bM-^@M-^], the check will not be executed.  The default is
             M-bM-^@M-^\yesM-bM-^@M-^].

     ^[[1mCipher  ^[[22mSpecifies the cipher to use for encrypting the session in protoM-bM-^@M-^P
             col version 1.  Currently, M-bM-^@M-^\blowfishM-bM-^@M-^], M-bM-^@M-^\3desM-bM-^@M-^], and M-bM-^@M-^\desM-bM-^@M-^] are supM-bM-^@M-^P
             ported.  ^[[4mdes^[[24m is only supported in the ^[[1mssh ^[[22mclient for interoperM-bM-^@M-^P
             ability with legacy protocol 1 implementations that do not supM-bM-^@M-^P
             port the ^[[4m3des^[[24m cipher.  Its use is strongly discouraged due to
             cryptographic weaknesses.  The default is M-bM-^@M-^\3desM-bM-^@M-^].

     ^[[1mCiphers^[[0m
             Specifies the ciphers allowed for protocol version 2 in order of
             preference.  Multiple ciphers must be commaM-bM-^@M-^Pseparated.  The
             default is

               M-bM-^@M-^XM-bM-^@M-^Xaes128M-bM-^@M-^Pcbc,3desM-bM-^@M-^Pcbc,blowfishM-bM-^@M-^Pcbc,cast128M-bM-^@M-^Pcbc,arcfour,
                 aes192M-bM-^@M-^Pcbc,aes256M-bM-^@M-^PcbcM-bM-^@M-^YM-bM-^@M-^Y

     ^[[1mClearAllForwardings^[[0m
             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 ^[[1mssh^[[0m
             command line to clear port forwardings set in configuration
             files, and is automatically set by scp(1) and sftp(1).  The arguM-bM-^@M-^P
             ment must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The default is M-bM-^@M-^\noM-bM-^@M-^].

     ^[[1mCompression^[[0m
             Specifies whether to use compression.  The argument must be M-bM-^@M-^\yesM-bM-^@M-^]
             or M-bM-^@M-^\noM-bM-^@M-^].  The default is M-bM-^@M-^\noM-bM-^@M-^].

     ^[[1mCompressionLevel^[[0m
             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.

     ^[[1mConnectionAttempts^[[0m
             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.

     ^[[1mDynamicForward^[[0m
             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-bM-^@M-^P
             col is supported, and ^[[1mssh ^[[22mwill 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-bM-^@M-^P
             leged ports.

     ^[[1mEscapeChar^[[0m
             Sets the escape character (default: M-bM-^@M-^X~M-bM-^@M-^Y).  The escape character
             can also be set on the command line.  The argument should be a
             single character, M-bM-^@M-^X^M-bM-^@M-^Y followed by a letter, or M-bM-^@M-^\noneM-bM-^@M-^] to disable
             the escape character entirely (making the connection transparent
             for binary data).

     ^[[1mForwardAgent^[[0m
             Specifies whether the connection to the authentication agent (if
             any) will be forwarded to the remote machine.  The argument must
             be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The default is M-bM-^@M-^\noM-bM-^@M-^].

             Agent forwarding should be enabled with caution.  Users with the
             ability to bypass file permissions on the remote host (for the
             agentM-bM-^@M-^Ys UnixM-bM-^@M-^Pdomain socket) can access the local agent through
             the forwarded connection.  An attacker cannot obtain key material
             from the agent, however they can perform operations on the keys
             that enable them to authenticate using the identities loaded into
             the agent.

     ^[[1mForwardX11^[[0m
             Specifies whether X11 connections will be automatically rediM-bM-^@M-^P
             rected over the secure channel and DISPLAY set.  The argument
             must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The default is M-bM-^@M-^\noM-bM-^@M-^].

             X11 forwarding should be enabled with caution.  Users with the
             ability to bypass file permissions on the remote host (for the
             userM-bM-^@M-^Ys X authorization database) can access the local X11 display
             through the forwarded connection.  An attacker may then be able
             to perform activities such as keystroke monitoring.

     ^[[1mGatewayPorts^[[0m
             Specifies whether remote hosts are allowed to connect to local
             forwarded ports.  By default, ^[[1mssh ^[[22mbinds local port forwardings to
             the loopback address.  This prevents other remote hosts from conM-bM-^@M-^P
             necting to forwarded ports.  ^[[1mGatewayPorts ^[[22mcan be used to specify
             that ^[[1mssh ^[[22mshould bind local port forwardings to the wildcard
             address, thus allowing remote hosts to connect to forwarded
             ports.  The argument must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The default is M-bM-^@M-^\noM-bM-^@M-^].

     ^[[1mGlobalKnownHostsFile^[[0m
             Specifies a file to use for the global host key database instead
             of ^[[4m/etc/ssh/ssh_known_hosts^[[24m.

     ^[[1mHostbasedAuthentication^[[0m
             Specifies whether to try rhosts based authentication with public
             key authentication.  The argument must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The
             default is M-bM-^@M-^\noM-bM-^@M-^].  This option applies to protocol version 2 only
             and is similar to ^[[1mRhostsRSAAuthentication^[[22m.

     ^[[1mHostKeyAlgorithms^[[0m
             Specifies the protocol version 2 host key algorithms that the
             client wants to use in order of preference.  The default for this
             option is: M-bM-^@M-^\sshM-bM-^@M-^Prsa,sshM-bM-^@M-^PdssM-bM-^@M-^].

     ^[[1mHostKeyAlias^[[0m
             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-bM-^@M-^P
             tions or for multiple servers running on a single host.

     ^[[1mHostName^[[0m
             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 ^[[1mHostName ^[[22mspecificaM-bM-^@M-^P
             tions).

     ^[[1mIdentityFile^[[0m
             Specifies a file from which the userM-bM-^@M-^Ys RSA or DSA authentication
             identity is read. The default is ^[[4m$HOME/.ssh/identity^[[24m for protocol
             version 1, and ^[[4m$HOME/.ssh/id_rsa^[[24m and ^[[4m$HOME/.ssh/id_dsa^[[24m for protoM-bM-^@M-^P
             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 userM-bM-^@M-^Ys home direcM-bM-^@M-^P
             tory.  It is possible to have multiple identity files specified
             in configuration files; all these identities will be tried in
             sequence.

     ^[[1mKeepAlive^[[0m
             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-bM-^@M-^P
             porarily, and some people find it annoying.

             The default is M-bM-^@M-^\yesM-bM-^@M-^] (to send keepalives), and the client will
             notice if the network goes down or the remote host dies.  This is
             important in scripts, and many users want it too.

             To disable keepalives, the value should be set to M-bM-^@M-^\noM-bM-^@M-^].

     ^[[1mKerberosAuthentication^[[0m
             Specifies whether Kerberos authentication will be used.  The
             argument to this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].

     ^[[1mKerberosTgtPassing^[[0m
             Specifies whether a Kerberos TGT will be forwarded to the server.
             This will only work if the Kerberos server is actually an AFS
             kaserver.  The argument to this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].

     ^[[1mLocalForward^[[0m
             Specifies that a TCP/IP port on the local machine be forwarded
             over the secure channel to the specified host and port from the
             remote machine.  The first argument must be a port number, and
             the second must be ^[[4mhost:port^[[24m.  IPv6 addresses can be specified
             with an alternative syntax: ^[[4mhost/port^[[24m.  Multiple forwardings may
             be specified, and additional forwardings can be given on the comM-bM-^@M-^P
             mand line.  Only the superuser can forward privileged ports.

     ^[[1mLogLevel^[[0m
             Gives the verbosity level that is used when logging messages from
             ^[[1mssh^[[22m.  The possible values are: QUIET, FATAL, ERROR, INFO, VERM-bM-^@M-^P
             BOSE, DEBUG, DEBUG1, DEBUG2 and DEBUG3.  The default is INFO.
             DEBUG and DEBUG1 are equivalent.  DEBUG2 and DEBUG3 each specify
             higher levels of verbose output.

     ^[[1mMACs    ^[[22mSpecifies the MAC (message authentication code) algorithms in
             order of preference.  The MAC algorithm is used in protocol verM-bM-^@M-^P
             sion 2 for data integrity protection.  Multiple algorithms must
             be commaM-bM-^@M-^Pseparated.  The default is
             M-bM-^@M-^\hmacM-bM-^@M-^Pmd5,hmacM-bM-^@M-^Psha1,hmacM-bM-^@M-^Pripemd160,hmacM-bM-^@M-^Psha1M-bM-^@M-^P96,hmacM-bM-^@M-^Pmd5M-bM-^@M-^P96M-bM-^@M-^].

     ^[[1mNoHostAuthenticationForLocalhost^[[0m
             This option can be used if the home directory is shared across
             machines.  In this case localhost will refer to a different
             machine on each of the machines and the user will get many warnM-bM-^@M-^P
             ings about changed host keys.  However, this option disables host
             authentication for localhost.  The argument to this keyword must
             be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The default is to check the host key for
             localhost.

     ^[[1mNumberOfPasswordPrompts^[[0m
             Specifies the number of password prompts before giving up.  The
             argument to this keyword must be an integer.  Default is 3.

     ^[[1mPasswordAuthentication^[[0m
             Specifies whether to use password authentication.  The argument
             to this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The default is M-bM-^@M-^\yesM-bM-^@M-^].

     ^[[1mPort    ^[[22mSpecifies the port number to connect on the remote host.  Default
             is 22.

     ^[[1mPreferredAuthentications^[[0m
             Specifies the order in which the client should try protocol 2
             authentication methods. This allows a client to prefer one method
             (e.g.  ^[[1mkeyboardM-bM-^@M-^Pinteractive^[[22m) over another method (e.g.  ^[[1mpassword^[[22m)
             The default for this option is:
             M-bM-^@M-^\hostbased,publickey,keyboardM-bM-^@M-^Pinteractive,passwordM-bM-^@M-^].

     ^[[1mProtocol^[[0m
             Specifies the protocol versions ^[[1mssh ^[[22mshould support in order of
             preference.  The possible values are M-bM-^@M-^\1M-bM-^@M-^] and M-bM-^@M-^\2M-bM-^@M-^].  Multiple verM-bM-^@M-^P
             sions must be commaM-bM-^@M-^Pseparated.  The default is M-bM-^@M-^\2,1M-bM-^@M-^].  This means
             that ^[[1mssh ^[[22mtries version 2 and falls back to version 1 if version 2
             is not available.

     ^[[1mProxyCommand^[[0m
             Specifies the command to use to connect to the server.  The comM-bM-^@M-^P
             mand string extends to the end of the line, and is executed with
             ^[[4m/bin/sh^[[24m.  In the command string, M-bM-^@M-^X%hM-bM-^@M-^Y will be substituted by the
             host name to connect and M-bM-^@M-^X%pM-bM-^@M-^Y by the port.  The command can be
             basically anything, and should read from its standard input and
             write to its standard output.  It should eventually connect an
             sshd(8) server running on some machine, or execute ^[[1msshd M-bM-^@M-^Pi ^[[22msomeM-bM-^@M-^P
             where.  Host key management will be done using the HostName of
             the host being connected (defaulting to the name typed by the
             user).  Setting the command to M-bM-^@M-^\noneM-bM-^@M-^] disables this option
             entirely.  Note that ^[[1mCheckHostIP ^[[22mis not available for connects
             with a proxy command.

     ^[[1mPubkeyAuthentication^[[0m
             Specifies whether to try public key authentication.  The argument
             to this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The default is M-bM-^@M-^\yesM-bM-^@M-^].
             This option applies to protocol version 2 only.

     ^[[1mRemoteForward^[[0m
             Specifies that a TCP/IP port on the remote machine be forwarded
             over the secure channel to the specified host and port from the
             local machine.  The first argument must be a port number, and the
             second must be ^[[4mhost:port^[[24m.  IPv6 addresses can be specified with
             an alternative syntax: ^[[4mhost/port^[[24m.  Multiple forwardings may be
             specified, and additional forwardings can be given on the command
             line.  Only the superuser can forward privileged ports.

     ^[[1mRhostsAuthentication^[[0m
             Specifies whether to try rhosts based authentication.  Note that
             this declaration only affects the client side and has no effect
             whatsoever on security.  Most servers do not permit RhostsAuthenM-bM-^@M-^P
             tication because it is not secure (see ^[[1mRhostsRSAAuthentication^[[22m).
             The argument to this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The default
             is M-bM-^@M-^\noM-bM-^@M-^].  This option applies to protocol version 1 only and
             requires ^[[1mssh ^[[22mto be setuid root and ^[[1mUsePrivilegedPort ^[[22mto be set to
             M-bM-^@M-^\yesM-bM-^@M-^].

     ^[[1mRhostsRSAAuthentication^[[0m
             Specifies whether to try rhosts based authentication with RSA
             host authentication.  The argument must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The
             default is M-bM-^@M-^\noM-bM-^@M-^].  This option applies to protocol version 1 only
             and requires ^[[1mssh ^[[22mto be setuid root.

     ^[[1mRSAAuthentication^[[0m
             Specifies whether to try RSA authentication.  The argument to
             this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  RSA authentication will only
             be attempted if the identity file exists, or an authentication
             agent is running.  The default is M-bM-^@M-^\yesM-bM-^@M-^].  Note that this option
             applies to protocol version 1 only.

     ^[[1mSmartcardDevice^[[0m
             Specifies which smartcard device to use. The argument to this
             keyword is the device ^[[1mssh ^[[22mshould use to communicate with a smartM-bM-^@M-^P
             card used for storing the userM-bM-^@M-^Ys private RSA key. By default, no
             device is specified and smartcard support is not activated.

     ^[[1mStrictHostKeyChecking^[[0m
             If this flag is set to M-bM-^@M-^\yesM-bM-^@M-^], ^[[1mssh ^[[22mwill never automatically add
             host keys to the ^[[4m$HOME/.ssh/known_hosts^[[24m file, and refuses to conM-bM-^@M-^P
             nect to hosts whose host key has changed.  This provides maximum
             protection against trojan horse attacks, however, can be annoying
             when the ^[[4m/etc/ssh/ssh_known_hosts^[[24m file is poorly maintained, or
             connections to new hosts are frequently made.  This option forces
             the user to manually add all new hosts.  If this flag is set to
             M-bM-^@M-^\noM-bM-^@M-^], ^[[1mssh ^[[22mwill automatically add new host keys to the user known
             hosts files.  If this flag is set to M-bM-^@M-^\askM-bM-^@M-^], new host keys will be
             added to the user known host files only after the user has conM-bM-^@M-^P
             firmed that is what they really want to do, and ^[[1mssh ^[[22mwill refuse
             to connect to hosts whose host key has changed.  The host keys of
             known hosts will be verified automatically in all cases.  The
             argument must be M-bM-^@M-^\yesM-bM-^@M-^], M-bM-^@M-^\noM-bM-^@M-^] or M-bM-^@M-^\askM-bM-^@M-^].  The default is M-bM-^@M-^\askM-bM-^@M-^].

     ^[[1mUsePrivilegedPort^[[0m
             Specifies whether to use a privileged port for outgoing connecM-bM-^@M-^P
             tions.  The argument must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^].  The default is M-bM-^@M-^\noM-bM-^@M-^].
             If set to M-bM-^@M-^\yesM-bM-^@M-^] ^[[1mssh ^[[22mmust be setuid root.  Note that this option
             must be set to M-bM-^@M-^\yesM-bM-^@M-^] if ^[[1mRhostsAuthentication ^[[22mand
             ^[[1mRhostsRSAAuthentication ^[[22mauthentications are needed with older
             servers.

     ^[[1mUser    ^[[22mSpecifies the user to log in as.  This can be useful when a difM-bM-^@M-^P
             ferent user name is used on different machines.  This saves the
             trouble of having to remember to give the user name on the comM-bM-^@M-^P
             mand line.

     ^[[1mUserKnownHostsFile^[[0m
             Specifies a file to use for the user host key database instead of
             ^[[4m$HOME/.ssh/known_hosts^[[24m.

     ^[[1mXAuthLocation^[[0m
             Specifies the full pathname of the xauth(1) program.  The default
             is ^[[4m/usr/X11R6/bin/xauth^[[24m.

^[[1mFILES^[[0m
     $HOME/.ssh/config
             This is the perM-bM-^@M-^Puser configuration file.  The format of this file
             is described above.  This file is used by the ^[[1mssh ^[[22mclient.  This
             file does not usually contain any sensitive information, but the
             recommended permissions are read/write for the user, and not
             accessible by others.

     /etc/ssh/ssh_config
             Systemwide configuration file.  This file provides defaults for
             those values that are not specified in the userM-bM-^@M-^Ys configuration
             file, and for those users who do not have a configuration file.
             This file must be worldM-bM-^@M-^Preadable.

^[[1mAUTHORS^[[0m
     OpenSSH is a derivative of the original and free ssh 1.2.12 release by
     Tatu Ylonen.  Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
     de Raadt and Dug Song removed many bugs, reM-bM-^@M-^Padded newer features and creM-bM-^@M-^P
     ated OpenSSH.  Markus Friedl contributed the support for SSH protocol
     versions 1.5 and 2.0.

^[[1mSEE ALSO^[[0m
     ssh(1)

BSD                           September 25, 1999                           BSD