ssh_config(5) — Linux manual page

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

NAME         top

     ssh_config — OpenSSH client configuration file

DESCRIPTION         top

     ssh(1) obtains configuration data from the following sources in the
     following order:

           1.   command-line options
           2.   user's configuration file (~/.ssh/config)
           3.   system-wide configuration file (/etc/ssh/ssh_config)

     For each parameter, the first obtained value will be used.  The
     configuration files contain sections separated 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 usually the one given on the command line (see the
     CanonicalizeHostname option for exceptions).

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

     The file contains keyword-argument pairs, one per line.  Lines
     starting with ‘#’ and empty lines are interpreted as comments.
     Arguments may optionally be enclosed in double quotes (") in order
     to represent arguments containing spaces.  Configuration options
     may be separated by whitespace or optional whitespace and exactly
     one ‘=’; the latter format is useful to avoid the need to quote
     whitespace when specifying configuration options using the ssh,
     scp, and sftp -o option.

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

     Host    Restricts the following declarations (up to the next Host
             or Match keyword) to be only for those hosts that match one
             of the patterns given after the keyword.  If more than one
             pattern is provided, they should be separated by
             whitespace.  A single ‘*’ as a pattern can be used to
             provide global defaults for all hosts.  The host is usually
             the hostname argument given on the command line (see the
             CanonicalizeHostname keyword for exceptions).

             A pattern entry may be negated by prefixing it with an
             exclamation mark (‘!’).  If a negated entry is matched,
             then the Host entry is ignored, regardless of whether any
             other patterns on the line match.  Negated matches are
             therefore useful to provide exceptions for wildcard
             matches.

             See PATTERNS for more information on patterns.

     Match   Restricts the following declarations (up to the next Host
             or Match keyword) to be used only when the conditions
             following the Match keyword are satisfied.  Match
             conditions are specified using one or more criteria or the
             single token all which always matches.  The available
             criteria keywords are: canonical, final, exec, host,
             originalhost, user, and localuser.  The all criteria must
             appear alone or immediately after canonical or final.
             Other criteria may be combined arbitrarily.  All criteria
             but all, canonical, and final require an argument.
             Criteria may be negated by prepending an exclamation mark
             (‘!’).

             The canonical keyword matches only when the configuration
             file is being re-parsed after hostname canonicalization
             (see the CanonicalizeHostname option).  This may be useful
             to specify conditions that work with canonical host names
             only.

             The final keyword requests that the configuration be re-
             parsed (regardless of whether CanonicalizeHostname is
             enabled), and matches only during this final pass.  If
             CanonicalizeHostname is enabled, then canonical and final
             match during the same pass.

             The exec keyword executes the specified command under the
             user's shell.  If the command returns a zero exit status
             then the condition is considered true.  Commands containing
             whitespace characters must be quoted.  Arguments to exec
             accept the tokens described in the TOKENS section.

             The other keywords' criteria must be single entries or
             comma-separated lists and may use the wildcard and negation
             operators described in the PATTERNS section.  The criteria
             for the host keyword are matched against the target
             hostname, after any substitution by the Hostname or
             CanonicalizeHostname options.  The originalhost keyword
             matches against the hostname as it was specified on the
             command-line.  The user keyword matches against the target
             username on the remote host.  The localuser keyword matches
             against the name of the local user running ssh(1) (this
             keyword may be useful in system-wide ssh_config files).

     AddKeysToAgent
             Specifies whether keys should be automatically added to a
             running ssh-agent(1).  If this option is set to yes and a
             key is loaded from a file, the key and its passphrase are
             added to the agent with the default lifetime, as if by
             ssh-add(1).  If this option is set to ask, ssh(1) will
             require confirmation using the SSH_ASKPASS program before
             adding a key (see ssh-add(1) for details).  If this option
             is set to confirm, each use of the key must be confirmed,
             as if the -c option was specified to ssh-add(1).  If this
             option is set to no, no keys are added to the agent.
             Alternately, this option may be specified as a time
             interval using the format described in the TIME FORMATS
             section of sshd_config(5) to specify the key's lifetime in
             ssh-agent(1), after which it will automatically be removed.
             The argument must be no (the default), yes, confirm
             (optionally followed by a time interval), ask or a time
             interval.

     AddressFamily
             Specifies which address family to use when connecting.
             Valid arguments are any (the default), inet (use IPv4
             only), or inet6 (use IPv6 only).

     BatchMode
             If set to yes, user interaction such as password prompts
             and host key confirmation requests will be disabled.  This
             option is useful in scripts and other batch jobs where no
             user is present to interact with ssh(1).  The argument must
             be yes or no (the default).

     BindAddress
             Use the specified address on the local machine as the
             source address of the connection.  Only useful on systems
             with more than one address.

     BindInterface
             Use the address of the specified interface on the local
             machine as the source address of the connection.

     CanonicalDomains
             When CanonicalizeHostname is enabled, this option specifies
             the list of domain suffixes in which to search for the
             specified destination host.

     CanonicalizeFallbackLocal
             Specifies whether to fail with an error when hostname
             canonicalization fails.  The default, yes, will attempt to
             look up the unqualified hostname using the system
             resolver's search rules.  A value of no will cause ssh(1)
             to fail instantly if CanonicalizeHostname is enabled and
             the target hostname cannot be found in any of the domains
             specified by CanonicalDomains.

     CanonicalizeHostname
             Controls whether explicit hostname canonicalization is
             performed.  The default, no, is not to perform any name
             rewriting and let the system resolver handle all hostname
             lookups.  If set to yes then, for connections that do not
             use a ProxyCommand or ProxyJump, ssh(1) will attempt to
             canonicalize the hostname specified on the command line
             using the CanonicalDomains suffixes and
             CanonicalizePermittedCNAMEs rules.  If CanonicalizeHostname
             is set to always, then canonicalization is applied to
             proxied connections too.

             If this option is enabled, then the configuration files are
             processed again using the new target name to pick up any
             new configuration in matching Host and Match stanzas.  A
             value of none disables the use of a ProxyJump host.

     CanonicalizeMaxDots
             Specifies the maximum number of dot characters in a
             hostname before canonicalization is disabled.  The default,
             1, allows a single dot (i.e. hostname.subdomain).

     CanonicalizePermittedCNAMEs
             Specifies rules to determine whether CNAMEs should be
             followed when canonicalizing hostnames.  The rules consist
             of one or more arguments of
             source_domain_list:target_domain_list, where
             source_domain_list is a pattern-list of domains that may
             follow CNAMEs in canonicalization, and target_domain_list
             is a pattern-list of domains that they may resolve to.

             For example,
             "*.a.example.com:*.b.example.com,*.c.example.com" will
             allow hostnames matching "*.a.example.com" to be
             canonicalized to names in the "*.b.example.com" or
             "*.c.example.com" domains.

     CASignatureAlgorithms
             Specifies which algorithms are allowed for signing of
             certificates by certificate authorities (CAs).  The default
             is:

                   ssh-ed25519,ecdsa-sha2-nistp256,
                   ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
                   sk-ssh-ed25519@openssh.com,
                   sk-ecdsa-sha2-nistp256@openssh.com,
                   rsa-sha2-512,rsa-sha2-256

             If the specified list begins with a ‘+’ character, then the
             specified algorithms will be appended to the default set
             instead of replacing them.  If the specified list begins
             with a ‘-’ character, then the specified algorithms
             (including wildcards) will be removed from the default set
             instead of replacing them.

             ssh(1) will not accept host certificates signed using
             algorithms other than those specified.

     CertificateFile
             Specifies a file from which the user's certificate is read.
             A corresponding private key must be provided separately in
             order to use this certificate either from an IdentityFile
             directive or -i flag to ssh(1), via ssh-agent(1), or via a
             PKCS11Provider or SecurityKeyProvider.

             Arguments to CertificateFile may use the tilde syntax to
             refer to a user's home directory, the tokens described in
             the TOKENS section and environment variables as described
             in the ENVIRONMENT VARIABLES section.

             It is possible to have multiple certificate files specified
             in configuration files; these certificates will be tried in
             sequence.  Multiple CertificateFile directives will add to
             the list of certificates used for authentication.

     CheckHostIP
             If set to yes ssh(1) will additionally check the host IP
             address in the known_hosts file.  This allows it to detect
             if a host key changed due to DNS spoofing and will add
             addresses of destination hosts to ~/.ssh/known_hosts in the
             process, regardless of the setting of
             StrictHostKeyChecking.  If the option is set to no (the
             default), the check will not be executed.

     Ciphers
             Specifies the ciphers allowed and their order of
             preference.  Multiple ciphers must be comma-separated.  If
             the specified list begins with a ‘+’ character, then the
             specified ciphers will be appended to the default set
             instead of replacing them.  If the specified list begins
             with a ‘-’ character, then the specified ciphers (including
             wildcards) will be removed from the default set instead of
             replacing them.  If the specified list begins with a ‘^’
             character, then the specified ciphers will be placed at the
             head of the default set.

             The supported ciphers are:

                   3des-cbc
                   aes128-cbc
                   aes192-cbc
                   aes256-cbc
                   aes128-ctr
                   aes192-ctr
                   aes256-ctr
                   aes128-gcm@openssh.com
                   aes256-gcm@openssh.com
                   chacha20-poly1305@openssh.com

             The default is:

                   chacha20-poly1305@openssh.com,
                   aes128-ctr,aes192-ctr,aes256-ctr,
                   aes128-gcm@openssh.com,aes256-gcm@openssh.com

             The list of available ciphers may also be obtained using
             "ssh -Q cipher".

     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(1) command line to clear port
             forwardings set in configuration files, and is
             automatically set by scp(1) and sftp(1).  The argument must
             be yes or no (the default).

     Compression
             Specifies whether to use compression.  The argument must be
             yes or no (the default).

     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.

     ConnectTimeout
             Specifies the timeout (in seconds) used when connecting to
             the SSH server, instead of using the default system TCP
             timeout.  This timeout is applied both to establishing the
             connection and to performing the initial SSH protocol
             handshake and key exchange.

     ControlMaster
             Enables the sharing of multiple sessions over a single
             network connection.  When set to yes, ssh(1) will listen
             for connections on a control socket specified using the
             ControlPath argument.  Additional sessions can connect to
             this socket using the same ControlPath with ControlMaster
             set to no (the default).  These sessions will try to reuse
             the master instance's network connection rather than
             initiating new ones, but will fall back to connecting
             normally if the control socket does not exist, or is not
             listening.

             Setting this to ask will cause ssh(1) to listen for control
             connections, but require confirmation using ssh-askpass(1).
             If the ControlPath cannot be opened, ssh(1) will continue
             without connecting to a master instance.

             X11 and ssh-agent(1) forwarding is supported over these
             multiplexed connections, however the display and agent
             forwarded will be the one belonging to the master
             connection i.e. it is not possible to forward multiple
             displays or agents.

             Two additional options allow for opportunistic
             multiplexing: try to use a master connection but fall back
             to creating a new one if one does not already exist.  These
             options are: auto and autoask.  The latter requires
             confirmation like the ask option.

     ControlPath
             Specify the path to the control socket used for connection
             sharing as described in the ControlMaster section above or
             the string none to disable connection sharing.  Arguments
             to ControlPath may use the tilde syntax to refer to a
             user's home directory, the tokens described in the TOKENS
             section and environment variables as described in the
             ENVIRONMENT VARIABLES section.  It is recommended that any
             ControlPath used for opportunistic connection sharing
             include at least %h, %p, and %r (or alternatively %C) and
             be placed in a directory that is not writable by other
             users.  This ensures that shared connections are uniquely
             identified.

     ControlPersist
             When used in conjunction with ControlMaster, specifies that
             the master connection should remain open in the background
             (waiting for future client connections) after the initial
             client connection has been closed.  If set to no (the
             default), then the master connection will not be placed
             into the background, and will close as soon as the initial
             client connection is closed.  If set to yes or 0, then the
             master connection will remain in the background
             indefinitely (until killed or closed via a mechanism such
             as the "ssh -O exit").  If set to a time in seconds, or a
             time in any of the formats documented in sshd_config(5),
             then the backgrounded master connection will automatically
             terminate after it has remained idle (with no client
             connections) for the specified time.

     DynamicForward
             Specifies that a TCP 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 [bind_address:]port.  IPv6 addresses
             can be specified by enclosing addresses in square brackets.
             By default, the local port is bound in accordance with the
             GatewayPorts setting.  However, an explicit bind_address
             may be used to bind the connection to a specific address.
             The bind_address of localhost indicates that the listening
             port be bound for local use only, while an empty address or
             ‘*’ indicates that the port should be available from all
             interfaces.

             Currently the SOCKS4 and SOCKS5 protocols are supported,
             and ssh(1) will act as a SOCKS server.  Multiple
             forwardings may be specified, and additional forwardings
             can be given on the command line.  Only the superuser can
             forward privileged ports.

     EnableSSHKeysign
             Setting this option to yes in the global client
             configuration file /etc/ssh/ssh_config enables the use of
             the helper program ssh-keysign(8) during
             HostbasedAuthentication.  The argument must be yes or no
             (the default).  This option should be placed in the non-
             hostspecific section.  See ssh-keysign(8) for more
             information.

     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 disable the escape character entirely
             (making the connection transparent for binary data).

     ExitOnForwardFailure
             Specifies whether ssh(1) should terminate the connection if
             it cannot set up all requested dynamic, tunnel, local, and
             remote port forwardings, (e.g. if either end is unable to
             bind and listen on a specified port).  Note that
             ExitOnForwardFailure does not apply to connections made
             over port forwardings and will not, for example, cause
             ssh(1) to exit if TCP connections to the ultimate
             forwarding destination fail.  The argument must be yes or
             no (the default).

     FingerprintHash
             Specifies the hash algorithm used when displaying key
             fingerprints.  Valid options are: md5 and sha256 (the
             default).

     ForkAfterAuthentication
             Requests ssh to go to background just before command
             execution.  This is useful if ssh is going to ask for
             passwords or passphrases, but the user wants it in the
             background.  This implies the StdinNull configuration
             option being set to “yes”.  The recommended way to start
             X11 programs at a remote site is with something like ssh -f
             host xterm, which is the same as ssh host xterm if the
             ForkAfterAuthentication configuration option is set to
             “yes”.

             If the ExitOnForwardFailure configuration option is set to
             “yes”, then a client started with the
             ForkAfterAuthentication configuration option being set to
             “yes” will wait for all remote port forwards to be
             successfully established before placing itself in the
             background.  The argument to this keyword must be yes (same
             as the -f option) or no (the default).

     ForwardAgent
             Specifies whether the connection to the authentication
             agent (if any) will be forwarded to the remote machine.
             The argument may be yes, no (the default), an explicit path
             to an agent socket or the name of an environment variable
             (beginning with ‘$’) in which to find the path.

             Agent forwarding should be enabled with caution.  Users
             with the ability to bypass file permissions on the remote
             host (for the agent's Unix-domain 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.

     ForwardX11
             Specifies whether X11 connections will be automatically
             redirected over the secure channel and DISPLAY set.  The
             argument must be yes or no (the default).

             X11 forwarding should be enabled with caution.  Users with
             the ability to bypass file permissions on the remote host
             (for the user's X11 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 if the ForwardX11Trusted option is
             also enabled.

     ForwardX11Timeout
             Specify a timeout for untrusted X11 forwarding using the
             format described in the TIME FORMATS section of
             sshd_config(5).  X11 connections received by ssh(1) after
             this time will be refused.  Setting ForwardX11Timeout to
             zero will disable the timeout and permit X11 forwarding for
             the life of the connection.  The default is to disable
             untrusted X11 forwarding after twenty minutes has elapsed.

     ForwardX11Trusted
             If this option is set to yes, remote X11 clients will have
             full access to the original X11 display.

             If this option is set to no (the default), remote X11
             clients will be considered untrusted and prevented from
             stealing or tampering with data belonging to trusted X11
             clients.  Furthermore, the xauth(1) token used for the
             session will be set to expire after 20 minutes.  Remote
             clients will be refused access after this time.

             See the X11 SECURITY extension specification for full
             details on the restrictions imposed on untrusted clients.

     GatewayPorts
             Specifies whether remote hosts are allowed to connect to
             local forwarded ports.  By default, ssh(1) binds local port
             forwardings to the loopback address.  This prevents other
             remote hosts from connecting 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).

     GlobalKnownHostsFile
             Specifies one or more files to use for the global host key
             database, separated by whitespace.  The default is
             /etc/ssh/ssh_known_hosts, /etc/ssh/ssh_known_hosts2.

     GSSAPIAuthentication
             Specifies whether user authentication based on GSSAPI is
             allowed.  The default is no.

     GSSAPIDelegateCredentials
             Forward (delegate) credentials to the server.  The default
             is no.

     HashKnownHosts
             Indicates that ssh(1) should hash host names and addresses
             when they are added to ~/.ssh/known_hosts.  These hashed
             names may be used normally by ssh(1) and sshd(8), but they
             do not visually reveal identifying information if the
             file's contents are disclosed.  The default is no.  Note
             that existing names and addresses in known hosts files will
             not be converted automatically, but may be manually hashed
             using ssh-keygen(1).

     HostbasedAcceptedAlgorithms
             Specifies the signature algorithms that will be used for
             hostbased authentication as a comma-separated list of
             patterns.  Alternately if the specified list begins with a
             ‘+’ character, then the specified signature algorithms will
             be appended to the default set instead of replacing them.
             If the specified list begins with a ‘-’ character, then the
             specified signature algorithms (including wildcards) will
             be removed from the default set instead of replacing them.
             If the specified list begins with a ‘^’ character, then the
             specified signature algorithms will be placed at the head
             of the default set.  The default for this option is:

                ssh-ed25519-cert-v01@openssh.com,
                ecdsa-sha2-nistp256-cert-v01@openssh.com,
                ecdsa-sha2-nistp384-cert-v01@openssh.com,
                ecdsa-sha2-nistp521-cert-v01@openssh.com,
                sk-ssh-ed25519-cert-v01@openssh.com,
                sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
                rsa-sha2-512-cert-v01@openssh.com,
                rsa-sha2-256-cert-v01@openssh.com,
                ssh-rsa-cert-v01@openssh.com,
                ssh-ed25519,
                ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
                sk-ssh-ed25519@openssh.com,
                sk-ecdsa-sha2-nistp256@openssh.com,
                rsa-sha2-512,rsa-sha2-256,ssh-rsa

             The -Q option of ssh(1) may be used to list supported
             signature algorithms.  This was formerly named
             HostbasedKeyTypes.

     HostbasedAuthentication
             Specifies whether to try rhosts based authentication with
             public key authentication.  The argument must be yes or no
             (the default).

     HostKeyAlgorithms
             Specifies the host key signature algorithms that the client
             wants to use in order of preference.  Alternately if the
             specified list begins with a ‘+’ character, then the
             specified signature algorithms will be appended to the
             default set instead of replacing them.  If the specified
             list begins with a ‘-’ character, then the specified
             signature algorithms (including wildcards) will be removed
             from the default set instead of replacing them.  If the
             specified list begins with a ‘^’ character, then the
             specified signature algorithms will be placed at the head
             of the default set.  The default for this option is:

                ssh-ed25519-cert-v01@openssh.com,
                ecdsa-sha2-nistp256-cert-v01@openssh.com,
                ecdsa-sha2-nistp384-cert-v01@openssh.com,
                ecdsa-sha2-nistp521-cert-v01@openssh.com,
                sk-ssh-ed25519-cert-v01@openssh.com,
                sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
                rsa-sha2-512-cert-v01@openssh.com,
                rsa-sha2-256-cert-v01@openssh.com,
                ssh-rsa-cert-v01@openssh.com,
                ssh-ed25519,
                ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
                sk-ecdsa-sha2-nistp256@openssh.com,
                sk-ssh-ed25519@openssh.com,
                rsa-sha2-512,rsa-sha2-256,ssh-rsa

             If hostkeys are known for the destination host then this
             default is modified to prefer their algorithms.

             The list of available signature algorithms may also be
             obtained using "ssh -Q HostKeyAlgorithms".

     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 and when validating host
             certificates.  This option is useful for tunneling SSH
             connections 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.  Arguments
             to Hostname accept the tokens described in the TOKENS
             section.  Numeric IP addresses are also permitted (both on
             the command line and in Hostname specifications).  The
             default is the name given on the command line.

     IdentitiesOnly
             Specifies that ssh(1) should only use the configured
             authentication identity and certificate files (either the
             default files, or those explicitly configured in the
             ssh_config files or passed on the ssh(1) command-line),
             even if ssh-agent(1) or a PKCS11Provider or
             SecurityKeyProvider offers more identities.  The argument
             to this keyword must be yes or no (the default).  This
             option is intended for situations where ssh-agent offers
             many different identities.

     IdentityAgent
             Specifies the UNIX-domain socket used to communicate with
             the authentication agent.

             This option overrides the SSH_AUTH_SOCK environment
             variable and can be used to select a specific agent.
             Setting the socket name to none disables the use of an
             authentication agent.  If the string "SSH_AUTH_SOCK" is
             specified, the location of the socket will be read from the
             SSH_AUTH_SOCK environment variable.  Otherwise if the
             specified value begins with a ‘$’ character, then it will
             be treated as an environment variable containing the
             location of the socket.

             Arguments to IdentityAgent may use the tilde syntax to
             refer to a user's home directory, the tokens described in
             the TOKENS section and environment variables as described
             in the ENVIRONMENT VARIABLES section.

     IdentityFile
             Specifies a file from which the user's DSA, ECDSA,
             authenticator-hosted ECDSA, Ed25519, authenticator-hosted
             Ed25519 or RSA authentication identity is read.  The
             default is ~/.ssh/id_dsa, ~/.ssh/id_ecdsa,
             ~/.ssh/id_ecdsa_sk, ~/.ssh/id_ed25519, ~/.ssh/id_ed25519_sk
             and ~/.ssh/id_rsa.  Additionally, any identities
             represented by the authentication agent will be used for
             authentication unless IdentitiesOnly is set.  If no
             certificates have been explicitly specified by
             CertificateFile, ssh(1) will try to load certificate
             information from the filename obtained by appending
             -cert.pub to the path of a specified IdentityFile.

             Arguments to IdentityFile may use the tilde syntax to refer
             to a user's home directory or the tokens described in the
             TOKENS section.

             It is possible to have multiple identity files specified in
             configuration files; all these identities will be tried in
             sequence.  Multiple IdentityFile directives will add to the
             list of identities tried (this behaviour differs from that
             of other configuration directives).

             IdentityFile may be used in conjunction with IdentitiesOnly
             to select which identities in an agent are offered during
             authentication.  IdentityFile may also be used in
             conjunction with CertificateFile in order to provide any
             certificate also needed for authentication with the
             identity.

     IgnoreUnknown
             Specifies a pattern-list of unknown options to be ignored
             if they are encountered in configuration parsing.  This may
             be used to suppress errors if ssh_config contains options
             that are unrecognised by ssh(1).  It is recommended that
             IgnoreUnknown be listed early in the configuration file as
             it will not be applied to unknown options that appear
             before it.

     Include
             Include the specified configuration file(s).  Multiple
             pathnames may be specified and each pathname may contain
             glob(7) wildcards and, for user configurations, shell-like
             ‘~’ references to user home directories.  Wildcards will be
             expanded and processed in lexical order.  Files without
             absolute paths are assumed to be in ~/.ssh if included in a
             user configuration file or /etc/ssh if included from the
             system configuration file.  Include directive may appear
             inside a Match or Host block to perform conditional
             inclusion.

     IPQoS   Specifies the IPv4 type-of-service or DSCP class for
             connections.  Accepted values are af11, af12, af13, af21,
             af22, af23, af31, af32, af33, af41, af42, af43, cs0, cs1,
             cs2, cs3, cs4, cs5, cs6, cs7, ef, le, lowdelay, throughput,
             reliability, a numeric value, or none to use the operating
             system default.  This option may take one or two arguments,
             separated by whitespace.  If one argument is specified, it
             is used as the packet class unconditionally.  If two values
             are specified, the first is automatically selected for
             interactive sessions and the second for non-interactive
             sessions.  The default is af21 (Low-Latency Data) for
             interactive sessions and cs1 (Lower Effort) for non-
             interactive sessions.

     KbdInteractiveAuthentication
             Specifies whether to use keyboard-interactive
             authentication.  The argument to this keyword must be yes
             (the default) or no.  ChallengeResponseAuthentication is a
             deprecated alias for this.

     KbdInteractiveDevices
             Specifies the list of methods to use in keyboard-
             interactive authentication.  Multiple method names must be
             comma-separated.  The default is to use the server
             specified list.  The methods available vary depending on
             what the server supports.  For an OpenSSH server, it may be
             zero or more of: bsdauth and pam.

     KexAlgorithms
             Specifies the available KEX (Key Exchange) algorithms.
             Multiple algorithms must be comma-separated.  If the
             specified list begins with a ‘+’ character, then the
             specified methods will be appended to the default set
             instead of replacing them.  If the specified list begins
             with a ‘-’ character, then the specified methods (including
             wildcards) will be removed from the default set instead of
             replacing them.  If the specified list begins with a ‘^’
             character, then the specified methods will be placed at the
             head of the default set.  The default is:

                   curve25519-sha256,curve25519-sha256@libssh.org,
                   ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
                   diffie-hellman-group-exchange-sha256,
                   diffie-hellman-group16-sha512,
                   diffie-hellman-group18-sha512,
                   diffie-hellman-group14-sha256

             The list of available key exchange algorithms may also be
             obtained using "ssh -Q kex".

     KnownHostsCommand
             Specifies a command to use to obtain a list of host keys,
             in addition to those listed in UserKnownHostsFile and
             GlobalKnownHostsFile.  This command is executed after the
             files have been read.  It may write host key lines to
             standard output in identical format to the usual files
             (described in the VERIFYING HOST KEYS section in ssh(1)).
             Arguments to KnownHostsCommand accept the tokens described
             in the TOKENS section.  The command may be invoked multiple
             times per connection: once when preparing the preference
             list of host key algorithms to use, again to obtain the
             host key for the requested host name and, if CheckHostIP is
             enabled, one more time to obtain the host key matching the
             server's address.  If the command exits abnormally or
             returns a non-zero exit status then the connection is
             terminated.

     LocalCommand
             Specifies a command to execute on the local machine after
             successfully connecting to the server.  The command string
             extends to the end of the line, and is executed with the
             user's shell.  Arguments to LocalCommand accept the tokens
             described in the TOKENS section.

             The command is run synchronously and does not have access
             to the session of the ssh(1) that spawned it.  It should
             not be used for interactive commands.

             This directive is ignored unless PermitLocalCommand has
             been enabled.

     LocalForward
             Specifies that a TCP port on the local machine be forwarded
             over the secure channel to the specified host and port from
             the remote machine.  The first argument specifies the
             listener and may be [bind_address:]port or a Unix domain
             socket path.  The second argument is the destination and
             may be host:hostport or a Unix domain socket path if the
             remote host supports it.

             IPv6 addresses can be specified by enclosing addresses in
             square brackets.  Multiple forwardings may be specified,
             and additional forwardings can be given on the command
             line.  Only the superuser can forward privileged ports.  By
             default, the local port is bound in accordance with the
             GatewayPorts setting.  However, an explicit bind_address
             may be used to bind the connection to a specific address.
             The bind_address of localhost indicates that the listening
             port be bound for local use only, while an empty address or
             ‘*’ indicates that the port should be available from all
             interfaces.  Unix domain socket paths may use the tokens
             described in the TOKENS section and environment variables
             as described in the ENVIRONMENT VARIABLES section.

     LogLevel
             Gives the verbosity level that is used when logging
             messages from ssh(1).  The possible values are: QUIET,
             FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and
             DEBUG3.  The default is INFO.  DEBUG and DEBUG1 are
             equivalent.  DEBUG2 and DEBUG3 each specify higher levels
             of verbose output.

     LogVerbose
             Specify one or more overrides to LogLevel.  An override
             consists of a pattern lists that matches the source file,
             function and line number to force detailed logging for.
             For example, an override pattern of:

                   kex.c:*:1000,*:kex_exchange_identification():*,packet.c:*

             would enable detailed logging for line 1000 of kex.c,
             everything in the kex_exchange_identification() function,
             and all code in the packet.c file.  This option is intended
             for debugging and no overrides are enabled by default.

     MACs    Specifies the MAC (message authentication code) algorithms
             in order of preference.  The MAC algorithm is used for data
             integrity protection.  Multiple algorithms must be comma-
             separated.  If the specified list begins with a ‘+’
             character, then the specified algorithms will be appended
             to the default set instead of replacing them.  If the
             specified list begins with a ‘-’ character, then the
             specified algorithms (including wildcards) will be removed
             from the default set instead of replacing them.  If the
             specified list begins with a ‘^’ character, then the
             specified algorithms will be placed at the head of the
             default set.

             The algorithms that contain "-etm" calculate the MAC after
             encryption (encrypt-then-mac).  These are considered safer
             and their use recommended.

             The default is:

                   umac-64-etm@openssh.com,umac-128-etm@openssh.com,
                   hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
                   hmac-sha1-etm@openssh.com,
                   umac-64@openssh.com,umac-128@openssh.com,
                   hmac-sha2-256,hmac-sha2-512,hmac-sha1

             The list of available MAC algorithms may also be obtained
             using "ssh -Q mac".

     NoHostAuthenticationForLocalhost
             Disable host authentication for localhost (loopback
             addresses).  The argument to this keyword must be yes or no
             (the default).

     NumberOfPasswordPrompts
             Specifies the number of password prompts before giving up.
             The argument to this keyword must be an integer.  The
             default is 3.

     PasswordAuthentication
             Specifies whether to use password authentication.  The
             argument to this keyword must be yes (the default) or no.

     PermitLocalCommand
             Allow local command execution via the LocalCommand option
             or using the !command escape sequence in ssh(1).  The
             argument must be yes or no (the default).

     PermitRemoteOpen
             Specifies the destinations to which remote TCP port
             forwarding is permitted when RemoteForward is used as a
             SOCKS proxy.  The forwarding specification must be one of
             the following forms:

                   PermitRemoteOpen host:port
                   PermitRemoteOpen IPv4_addr:port
                   PermitRemoteOpen [IPv6_addr]:port

             Multiple forwards may be specified by separating them with
             whitespace.  An argument of any can be used to remove all
             restrictions and permit any forwarding requests.  An
             argument of none can be used to prohibit all forwarding
             requests.  The wildcard ‘*’ can be used for host or port to
             allow all hosts or ports respectively.  Otherwise, no
             pattern matching or address lookups are performed on
             supplied names.

     PKCS11Provider
             Specifies which PKCS#11 provider to use or none to indicate
             that no provider should be used (the default).  The
             argument to this keyword is a path to the PKCS#11 shared
             library ssh(1) should use to communicate with a PKCS#11
             token providing keys for user authentication.

     Port    Specifies the port number to connect on the remote host.
             The default is 22.

     PreferredAuthentications
             Specifies the order in which the client should try
             authentication methods.  This allows a client to prefer one
             method (e.g. keyboard-interactive) over another method
             (e.g. password).  The default is:

                   gssapi-with-mic,hostbased,publickey,
                   keyboard-interactive,password

     ProxyCommand
             Specifies the command to use to connect to the server.  The
             command string extends to the end of the line, and is
             executed using the user's shell ‘exec’ directive to avoid a
             lingering shell process.

             Arguments to ProxyCommand accept the tokens described in
             the TOKENS section.  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 sshd -i
             somewhere.  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 none
             disables this option entirely.  Note that CheckHostIP is
             not available for connects with a proxy command.

             This directive is useful in conjunction with nc(1) and its
             proxy support.  For example, the following directive would
             connect via an HTTP proxy at 192.0.2.0:

                ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p

     ProxyJump
             Specifies one or more jump proxies as either
             [user@]host[:port] or an ssh URI.  Multiple proxies may be
             separated by comma characters and will be visited
             sequentially.  Setting this option will cause ssh(1) to
             connect to the target host by first making a ssh(1)
             connection to the specified ProxyJump host and then
             establishing a TCP forwarding to the ultimate target from
             there.  Setting the host to none disables this option
             entirely.

             Note that this option will compete with the ProxyCommand
             option - whichever is specified first will prevent later
             instances of the other from taking effect.

             Note also that the configuration for the destination host
             (either supplied via the command-line or the configuration
             file) is not generally applied to jump hosts.
             ~/.ssh/config should be used if specific configuration is
             required for jump hosts.

     ProxyUseFdpass
             Specifies that ProxyCommand will pass a connected file
             descriptor back to ssh(1) instead of continuing to execute
             and pass data.  The default is no.

     PubkeyAcceptedAlgorithms
             Specifies the signature algorithms that will be used for
             public key authentication as a comma-separated list of
             patterns.  If the specified list begins with a ‘+’
             character, then the algorithms after it will be appended to
             the default instead of replacing it.  If the specified list
             begins with a ‘-’ character, then the specified algorithms
             (including wildcards) will be removed from the default set
             instead of replacing them.  If the specified list begins
             with a ‘^’ character, then the specified algorithms will be
             placed at the head of the default set.  The default for
             this option is:

                ssh-ed25519-cert-v01@openssh.com,
                ecdsa-sha2-nistp256-cert-v01@openssh.com,
                ecdsa-sha2-nistp384-cert-v01@openssh.com,
                ecdsa-sha2-nistp521-cert-v01@openssh.com,
                sk-ssh-ed25519-cert-v01@openssh.com,
                sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
                rsa-sha2-512-cert-v01@openssh.com,
                rsa-sha2-256-cert-v01@openssh.com,
                ssh-rsa-cert-v01@openssh.com,
                ssh-ed25519,
                ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
                sk-ssh-ed25519@openssh.com,
                sk-ecdsa-sha2-nistp256@openssh.com,
                rsa-sha2-512,rsa-sha2-256,ssh-rsa

             The list of available signature algorithms may also be
             obtained using "ssh -Q PubkeyAcceptedAlgorithms".

     PubkeyAuthentication
             Specifies whether to try public key authentication.  The
             argument to this keyword must be yes (the default) or no.

     RekeyLimit
             Specifies the maximum amount of data that may be
             transmitted before the session key is renegotiated,
             optionally followed by a maximum amount of time that may
             pass before the session key is renegotiated.  The first
             argument is specified in bytes and may have a suffix of
             ‘K’, ‘M’, or ‘G’ to indicate Kilobytes, Megabytes, or
             Gigabytes, respectively.  The default is between ‘1G’ and
             ‘4G’, depending on the cipher.  The optional second value
             is specified in seconds and may use any of the units
             documented in the TIME FORMATS section of sshd_config(5).
             The default value for RekeyLimit is default none, which
             means that rekeying is performed after the cipher's default
             amount of data has been sent or received and no time based
             rekeying is done.

     RemoteCommand
             Specifies a command to execute on the remote machine after
             successfully connecting to the server.  The command string
             extends to the end of the line, and is executed with the
             user's shell.  Arguments to RemoteCommand accept the tokens
             described in the TOKENS section.

     RemoteForward
             Specifies that a TCP port on the remote machine be
             forwarded over the secure channel.  The remote port may
             either be forwarded to a specified host and port from the
             local machine, or may act as a SOCKS 4/5 proxy that allows
             a remote client to connect to arbitrary destinations from
             the local machine.  The first argument is the listening
             specification and may be [bind_address:]port or, if the
             remote host supports it, a Unix domain socket path.  If
             forwarding to a specific destination then the second
             argument must be host:hostport or a Unix domain socket
             path, otherwise if no destination argument is specified
             then the remote forwarding will be established as a SOCKS
             proxy.  When acting as a SOCKS proxy the destination of the
             connection can be restricted by PermitRemoteOpen.

             IPv6 addresses can be specified by enclosing addresses in
             square brackets.  Multiple forwardings may be specified,
             and additional forwardings can be given on the command
             line.  Privileged ports can be forwarded only when logging
             in as root on the remote machine.  Unix domain socket paths
             may use the tokens described in the TOKENS section and
             environment variables as described in the ENVIRONMENT
             VARIABLES section.

             If the port argument is 0, the listen port will be
             dynamically allocated on the server and reported to the
             client at run time.

             If the bind_address is not specified, the default is to
             only bind to loopback addresses.  If the bind_address is
             ‘*’ or an empty string, then the forwarding is requested to
             listen on all interfaces.  Specifying a remote bind_address
             will only succeed if the server's GatewayPorts option is
             enabled (see sshd_config(5)).

     RequestTTY
             Specifies whether to request a pseudo-tty for the session.
             The argument may be one of: no (never request a TTY), yes
             (always request a TTY when standard input is a TTY), force
             (always request a TTY) or auto (request a TTY when opening
             a login session).  This option mirrors the -t and -T flags
             for ssh(1).

     RevokedHostKeys
             Specifies revoked host public keys.  Keys listed in this
             file will be refused for host authentication.  Note that if
             this file does not exist or is not readable, then host
             authentication will be refused for all hosts.  Keys may be
             specified as a text file, listing one public key per line,
             or as an OpenSSH Key Revocation List (KRL) as generated by
             ssh-keygen(1).  For more information on KRLs, see the KEY
             REVOCATION LISTS section in ssh-keygen(1).

     SecurityKeyProvider
             Specifies a path to a library that will be used when
             loading any FIDO authenticator-hosted keys, overriding the
             default of using the built-in USB HID support.

             If the specified value begins with a ‘$’ character, then it
             will be treated as an environment variable containing the
             path to the library.

     SendEnv
             Specifies what variables from the local environ(7) should
             be sent to the server.  The server must also support it,
             and the server must be configured to accept these
             environment variables.  Note that the TERM environment
             variable is always sent whenever a pseudo-terminal is
             requested as it is required by the protocol.  Refer to
             AcceptEnv in sshd_config(5) for how to configure the
             server.  Variables are specified by name, which may contain
             wildcard characters.  Multiple environment variables may be
             separated by whitespace or spread across multiple SendEnv
             directives.

             See PATTERNS for more information on patterns.

             It is possible to clear previously set SendEnv variable
             names by prefixing patterns with -.  The default is not to
             send any environment variables.

     ServerAliveCountMax
             Sets the number of server alive messages (see below) which
             may be sent without ssh(1) receiving any messages back from
             the server.  If this threshold is reached while server
             alive messages are being sent, ssh will disconnect from the
             server, terminating the session.  It is important to note
             that the use of server alive messages is very different
             from TCPKeepAlive (below).  The server alive messages are
             sent through the encrypted channel and therefore will not
             be spoofable.  The TCP keepalive option enabled by
             TCPKeepAlive is spoofable.  The server alive mechanism is
             valuable when the client or server depend on knowing when a
             connection has become unresponsive.

             The default value is 3.  If, for example,
             ServerAliveInterval (see below) is set to 15 and
             ServerAliveCountMax is left at the default, if the server
             becomes unresponsive, ssh will disconnect after
             approximately 45 seconds.

     ServerAliveInterval
             Sets a timeout interval in seconds after which if no data
             has been received from the server, ssh(1) will send a
             message through the encrypted channel to request a response
             from the server.  The default is 0, indicating that these
             messages will not be sent to the server.

     SessionType
             May be used to either request invocation of a subsystem on
             the remote system, or to prevent the execution of a remote
             command at all.  The latter is useful for just forwarding
             ports.  The argument to this keyword must be none (same as
             the -N option), subsystem (same as the -s option) or
             default (shell or command execution).

     SetEnv  Directly specify one or more environment variables and
             their contents to be sent to the server.  Similarly to
             SendEnv, with the exception of the TERM variable, the
             server must be prepared to accept the environment variable.

     StdinNull
             Redirects stdin from /dev/null (actually, prevents reading
             from stdin).  Either this or the equivalent -n option must
             be used when ssh is run in the background.  The argument to
             this keyword must be yes (same as the -n option) or no (the
             default).

     StreamLocalBindMask
             Sets the octal file creation mode mask (umask) used when
             creating a Unix-domain socket file for local or remote port
             forwarding.  This option is only used for port forwarding
             to a Unix-domain socket file.

             The default value is 0177, which creates a Unix-domain
             socket file that is readable and writable only by the
             owner.  Note that not all operating systems honor the file
             mode on Unix-domain socket files.

     StreamLocalBindUnlink
             Specifies whether to remove an existing Unix-domain socket
             file for local or remote port forwarding before creating a
             new one.  If the socket file already exists and
             StreamLocalBindUnlink is not enabled, ssh will be unable to
             forward the port to the Unix-domain socket file.  This
             option is only used for port forwarding to a Unix-domain
             socket file.

             The argument must be yes or no (the default).

     StrictHostKeyChecking
             If this flag is set to yes, ssh(1) will never automatically
             add host keys to the ~/.ssh/known_hosts file, and refuses
             to connect to hosts whose host key has changed.  This
             provides maximum protection against man-in-the-middle
             (MITM) attacks, though it can be annoying when the
             /etc/ssh/ssh_known_hosts file is poorly maintained or when
             connections to new hosts are frequently made.  This option
             forces the user to manually add all new hosts.

             If this flag is set to “accept-new” then ssh will
             automatically add new host keys to the user's known_hosts
             file, but will not permit connections to hosts with changed
             host keys.  If this flag is set to “no” or “off”, ssh will
             automatically add new host keys to the user known hosts
             files and allow connections to hosts with changed hostkeys
             to proceed, subject to some restrictions.  If this flag is
             set to ask (the default), new host keys will be added to
             the user known host files only after the user has confirmed
             that is what they really want to do, and ssh will refuse to
             connect to hosts whose host key has changed.  The host keys
             of known hosts will be verified automatically in all cases.

     SyslogFacility
             Gives the facility code that is used when logging messages
             from ssh(1).  The possible values are: DAEMON, USER, AUTH,
             LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6,
             LOCAL7.  The default is USER.

     TCPKeepAlive
             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 temporarily, and some people find it
             annoying.

             The default is yes (to send TCP keepalive messages), 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 TCP keepalive messages, the value should be set
             to no.  See also ServerAliveInterval for protocol-level
             keepalives.

     Tunnel  Request tun(4) device forwarding between the client and the
             server.  The argument must be yes, point-to-point (layer
             3), ethernet (layer 2), or no (the default).  Specifying
             yes requests the default tunnel mode, which is
             point-to-point.

     TunnelDevice
             Specifies the tun(4) devices to open on the client
             (local_tun) and the server (remote_tun).

             The argument must be local_tun[:remote_tun].  The devices
             may be specified by numerical ID or the keyword any, which
             uses the next available tunnel device.  If remote_tun is
             not specified, it defaults to any.  The default is any:any.

     UpdateHostKeys
             Specifies whether ssh(1) should accept notifications of
             additional hostkeys from the server sent after
             authentication has completed and add them to
             UserKnownHostsFile.  The argument must be yes, no or ask.
             This option allows learning alternate hostkeys for a server
             and supports graceful key rotation by allowing a server to
             send replacement public keys before old ones are removed.

             Additional hostkeys are only accepted if the key used to
             authenticate the host was already trusted or explicitly
             accepted by the user, the host was authenticated via
             UserKnownHostsFile (i.e. not GlobalKnownHostsFile) and the
             host was authenticated using a plain key and not a
             certificate.

             UpdateHostKeys is enabled by default if the user has not
             overridden the default UserKnownHostsFile setting and has
             not enabled VerifyHostKeyDNS, otherwise UpdateHostKeys will
             be set to no.

             If UpdateHostKeys is set to ask, then the user is asked to
             confirm the modifications to the known_hosts file.
             Confirmation is currently incompatible with ControlPersist,
             and will be disabled if it is enabled.

             Presently, only sshd(8) from OpenSSH 6.8 and greater
             support the "hostkeys@openssh.com" protocol extension used
             to inform the client of all the server's hostkeys.

     User    Specifies the user to log in as.  This can be useful when a
             different user name is used on different machines.  This
             saves the trouble of having to remember to give the user
             name on the command line.

     UserKnownHostsFile
             Specifies one or more files to use for the user host key
             database, separated by whitespace.  Each filename may use
             tilde notation to refer to the user's home directory, the
             tokens described in the TOKENS section and environment
             variables as described in the ENVIRONMENT VARIABLES
             section.  The default is ~/.ssh/known_hosts,
             ~/.ssh/known_hosts2.

     VerifyHostKeyDNS
             Specifies whether to verify the remote key using DNS and
             SSHFP resource records.  If this option is set to yes, the
             client will implicitly trust keys that match a secure
             fingerprint from DNS.  Insecure fingerprints will be
             handled as if this option was set to ask.  If this option
             is set to ask, information on fingerprint match will be
             displayed, but the user will still need to confirm new host
             keys according to the StrictHostKeyChecking option.  The
             default is no.

             See also VERIFYING HOST KEYS in ssh(1).

     VisualHostKey
             If this flag is set to yes, an ASCII art representation of
             the remote host key fingerprint is printed in addition to
             the fingerprint string at login and for unknown host keys.
             If this flag is set to no (the default), no fingerprint
             strings are printed at login and only the fingerprint
             string will be printed for unknown host keys.

     XAuthLocation
             Specifies the full pathname of the xauth(1) program.  The
             default is /usr/X11R6/bin/xauth.

PATTERNS         top

     A pattern consists of zero or more non-whitespace characters, ‘*’
     (a wildcard that matches zero or more characters), or ‘?’ (a
     wildcard that matches exactly one character).  For example, to
     specify a set of declarations for any host in the ".co.uk" set of
     domains, the following pattern could be used:

           Host *.co.uk

     The following pattern would match any host in the 192.168.0.[0-9]
     network range:

           Host 192.168.0.?

     A pattern-list is a comma-separated list of patterns.  Patterns
     within pattern-lists may be negated by preceding them with an
     exclamation mark (‘!’).  For example, to allow a key to be used
     from anywhere within an organization except from the "dialup" pool,
     the following entry (in authorized_keys) could be used:

           from="!*.dialup.example.com,*.example.com"

     Note that a negated match will never produce a positive result by
     itself.  For example, attempting to match "host3" against the
     following pattern-list will fail:

           from="!host1,!host2"

     The solution here is to include a term that will yield a positive
     match, such as a wildcard:

           from="!host1,!host2,*"

TOKENS         top

     Arguments to some keywords can make use of tokens, which are
     expanded at runtime:

           %%    A literal ‘%’.
           %C    Hash of %l%h%p%r.
           %d    Local user's home directory.
           %f    The fingerprint of the server's host key.
           %H    The known_hosts hostname or address that is being
                 searched for.
           %h    The remote hostname.
           %I    A string describing the reason for a KnownHostsCommand
                 execution: either ADDRESS when looking up a host by
                 address (only when CheckHostIP is enabled), HOSTNAME
                 when searching by hostname, or ORDER when preparing the
                 host key algorithm preference list to use for the
                 destination host.
           %i    The local user ID.
           %K    The base64 encoded host key.
           %k    The host key alias if specified, otherwise the original
                 remote hostname given on the command line.
           %L    The local hostname.
           %l    The local hostname, including the domain name.
           %n    The original remote hostname, as given on the command
                 line.
           %p    The remote port.
           %r    The remote username.
           %T    The local tun(4) or tap(4) network interface assigned
                 if tunnel forwarding was requested, or "NONE"
                 otherwise.
           %t    The type of the server host key, e.g.  ssh-ed25519.
           %u    The local username.

     CertificateFile, ControlPath, IdentityAgent, IdentityFile,
     KnownHostsCommand, LocalForward, Match exec, RemoteCommand,
     RemoteForward, and UserKnownHostsFile accept the tokens %%, %C, %d,
     %h, %i, %k, %L, %l, %n, %p, %r, and %u.

     KnownHostsCommand additionally accepts the tokens %f, %H, %I, %K
     and %t.

     Hostname accepts the tokens %% and %h.

     LocalCommand accepts all tokens.

     ProxyCommand accepts the tokens %%, %h, %n, %p, and %r.

ENVIRONMENT VARIABLES         top

     Arguments to some keywords can be expanded at runtime from
     environment variables on the client by enclosing them in ${}, for
     example ${HOME}/.ssh would refer to the user's .ssh directory.  If
     a specified environment variable does not exist then an error will
     be returned and the setting for that keyword will be ignored.

     The keywords CertificateFile, ControlPath, IdentityAgent,
     IdentityFile, KnownHostsCommand, and UserKnownHostsFile support
     environment variables.  The keywords LocalForward and RemoteForward
     support environment variables only for Unix domain socket paths.

FILES         top

     ~/.ssh/config
             This is the per-user configuration file.  The format of
             this file is described above.  This file is used by the SSH
             client.  Because of the potential for abuse, this file must
             have strict permissions: read/write for the user, and not
             writable by others.

     /etc/ssh/ssh_config
             Systemwide configuration file.  This file provides defaults
             for those values that are not specified in the user's
             configuration file, and for those users who do not have a
             configuration file.  This file must be world-readable.

SEE ALSO         top

     ssh(1)

AUTHORS         top

     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, re-added
     newer features and created OpenSSH.  Markus Friedl contributed the
     support for SSH protocol versions 1.5 and 2.0.

COLOPHON         top

     This page is part of the openssh (Portable OpenSSH) project.
     Information about the project can be found at
     http://www.openssh.com/portable.html.  If you have a bug report for
     this manual page, see ⟨http://www.openssh.com/report.html⟩.  This
     page was obtained from the tarball openssh-8.7p1.tar.gz fetched
     from ⟨http://ftp.eu.openbsd.org/pub/OpenBSD/OpenSSH/portable/⟩ on
     2021-08-27.  If you discover any rendering problems in this HTML
     version of the page, or you believe there is a better or more up-
     to-date source for the page, or you have corrections or
     improvements to the information in this COLOPHON (which is not part
     of the original manual page), send a mail to man-pages@man7.org

BSD                          August 12, 2021                         BSD