ssh_config

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

NAME
     ssh_config — OpenSSH client configuration file

DESCRIPTION
     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.

             A single argument of "none" causes no CNAMEs to be considered for
             canonicalization.  This is the default behaviour.

     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-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

             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-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

             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 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 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-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

             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/bin/xauth.

PATTERNS
     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
     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
     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
     ~/.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
     ssh(1)

AUTHORS
     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.

BSD                            September 25, 2021                            BSD