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

NAME
     ssh_config -- OpenSSH SSH client configuration files

SYNOPSIS
     ~/.ssh/config
     /etc/ssh/ssh_config

DESCRIPTION
     ssh(1) obtains configuration data from the following sources in the fol-
     lowing 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 configu-
     ration 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-spe-
     cific 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 argu-
     ments 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 configu-
     ration options using the ssh, scp, and sftp -o option.

     The possible keywords and their meanings are as follows (note that key-
     words 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 excep-
	     tions).

	     A pattern entry may be negated by prefixing it with an exclama-
	     tion 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, exec,
	     host, originalhost, user, and localuser.  The all criteria must
	     appear alone or immediately after canonical.  Other criteria may
	     be combined arbitrarily.  All criteria but all and canonical
	     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 con-
	     ditions that work with canonical host names only.	The exec key-
	     word executes the specified command under the user's shell.  If
	     the command returns a zero exit status then the condition is con-
	     sidered 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-sep-
	     arated 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 sub-
	     stitution by the Hostname or CanonicalizeHostname options.	 The
	     originalhost keyword matches against the hostname as it was spec-
	     ified 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.	 The argument must be yes, confirm, ask, or no (the
	     default).

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

     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.  Note that this option does not work if
	     UsePrivilegedPort is set to yes.

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

     CanonicalizeFallbackLocal
	     Specifies whether to fail with an error when hostname canonical-
	     ization 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, 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 con-
	     nections too.

	     If this option is enabled, then the configuration files are pro-
	     cessed again using the new target name to pick up any new config-
	     uration in matching Host and Match stanzas.

     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 canonical-
	     ized to names in the "*.b.example.com" or "*.c.example.com"
	     domains.

     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.

	     Arguments to CertificateFile 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 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.

     ChallengeResponseAuthentication
	     Specifies whether to use challenge-response authentication.  The
	     argument to this keyword must be yes (the default) or no.

     CheckHostIP
	     If set to yes (the default), 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 check will not be executed.

     Cipher  Specifies the cipher to use for encrypting the session in proto-
	     col version 1.  Currently, blowfish, 3des (the default), and des
	     are supported, though des is only supported in the ssh(1) client
	     for interoperability with legacy protocol 1 implementations; its
	     use is strongly discouraged due to cryptographic weaknesses.

     Ciphers
	     Specifies the ciphers allowed for protocol version 2 in order of
	     preference.  Multiple ciphers must be comma-separated.  If the
	     specified value begins with a `+' character, then the specified
	     ciphers will be appended to the default set instead of replacing
	     them.

	     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
		   arcfour
		   arcfour128
		   arcfour256
		   blowfish-cbc
		   cast128-cbc
		   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,
		   aes128-cbc,aes192-cbc,aes256-cbc

	     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 configura-
	     tion 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).

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

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

     ConnectTimeout
	     Specifies the timeout (in seconds) used when connecting to the
	     SSH server, instead of using the default system TCP timeout.
	     This value is used only when the target is down or really
	     unreachable, not when it refuses the connection.

     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 connec-
	     tion rather than initiating new ones, but will fall back to con-
	     necting normally if the control socket does not exist, or is not
	     listening.

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

	     X11 and ssh-agent(1) forwarding is supported over these multi-
	     plexed connections, however the display and agent forwarded will
	     be the one belonging to the master connection i.e. it is not pos-
	     sible 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 shar-
	     ing 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 or the
	     tokens described in the TOKENS 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 connec-
	     tion has been closed.  If set to no, 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 indefi-
	     nitely (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 mas-
	     ter 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 set-
	     ting.  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 informa-
	     tion.

     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 lis-
	     ten 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 ulti-
	     mate forwarding destination fail.	The argument must be yes or no
	     (the default).

     FingerprintHash
	     Specifies the hash algorithms used when displaying key finger-
	     prints.  Valid options are: md5 and sha256.  The default is
	     sha256 md5.

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

	     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 redi-
	     rected 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 dis-
	     play 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.
	     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 tam-
	     pering 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 spec-
	     ify 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 data-
	     base, 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.

     GSSAPIClientIdentity
	     If set, specifies the GSSAPI client identity that ssh should use
	     when connecting to the server. The default is unset, which means
	     that the default identity will be used.

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

     GSSAPIKeyExchange
	     Specifies whether key exchange based on GSSAPI may be used. When
	     using GSSAPI key exchange the server need not have a host key.
	     The default is ``no''.

     GSSAPIRenewalForcesRekey
	     If set to ``yes'' then renewal of the client's GSSAPI credentials
	     will force the rekeying of the ssh connection. With a compatible
	     server, this can delegate the renewed credentials to a session on
	     the server.  The default is ``no''.

     GSSAPIServerIdentity
	     If set, specifies the GSSAPI server identity that ssh should
	     expect when connecting to the server. The default is unset, which
	     means that the expected GSSAPI server identity will be determined
	     from the target hostname.

     GSSAPITrustDns
	     Set to ``yes to indicate that the DNS is trusted to securely
	     canonicalize'' the name of the host being connected to. If ``no,
	     the hostname entered on the'' command line will be passed
	     untouched to the GSSAPI library.  The default is ``no''.

     GSSAPIKexAlgorithms
	     The list of key exchange algorithms that are offered for GSSAPI
	     key exchange. Possible values are

		gss-gex-sha1-,
		gss-group1-sha1-,
		gss-group14-sha1-

	     The default is
	     ``gss-gex-sha1-,gss-group1-sha1-,gss-group14-sha1-''.  This
	     option only applies to protocol version 2 connections using GSS-
	     API.

     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 reveal iden-
	     tifying information should the file's contents be disclosed.  The
	     default is no.  Note that existing names and addresses in known
	     hosts files will not be converted automatically, but may be manu-
	     ally hashed using ssh-keygen(1).

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

     HostbasedKeyTypes
	     Specifies the key types that will be used for hostbased authenti-
	     cation as a comma-separated pattern list.	Alternately if the
	     specified value begins with a `+' character, then the specified
	     key types will be appended to the default set instead of replac-
	     ing them.	The default for this option is:

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

	     The -Q option of ssh(1) may be used to list supported key types.

     HostKeyAlgorithms
	     Specifies the host key algorithms that the client wants to use in
	     order of preference.  Alternately if the specified value begins
	     with a `+' character, then the specified key types will be
	     appended to the default set instead of replacing them.  The
	     default for this option is:

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

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

	     The list of available key types may also be obtained using "ssh
	     -Q key".

     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 data-
	     base files.  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 authentication identity
	     and certificate files explicitly configured in the ssh_config
	     files or passed on the ssh(1) command-line, even if ssh-agent(1)
	     or a PKCS11Provider 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.

	     Arguments to IdentityAgent may use the tilde syntax to refer to a
	     user's home directory or the tokens described in the TOKENS sec-
	     tion.

     IdentityFile
	     Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA
	     authentication identity is read.  The default is ~/.ssh/identity
	     for protocol version 1, and ~/.ssh/id_dsa, ~/.ssh/id_ecdsa,
	     ~/.ssh/id_ed25519 and ~/.ssh/id_rsa for protocol version 2.
	     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 sec-
	     tion.

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

	     IdentityFile may be used in conjunction with IdentitiesOnly to
	     select which identities in an agent are offered during authenti-
	     cation.  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 unrecog-
	     nised 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(3) wildcards
	     and, for user configurations, shell-like `~' references to user
	     home directories.	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, lowdelay, throughput, reliability, or a numeric value.
	     This option may take one or two arguments, separated by white-
	     space.  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 lowdelay for inter-
	     active sessions and throughput for non-interactive sessions.

     KbdInteractiveAuthentication
	     Specifies whether to use keyboard-interactive authentication.
	     The argument to this keyword must be yes (the default) or no.

     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, pam, and
	     skey.

     KexAlgorithms
	     Specifies the available KEX (Key Exchange) algorithms.  Multiple
	     algorithms must be comma-separated.  Alternately if the specified
	     value begins with a `+' character, then the specified methods
	     will be appended to the default set instead of replacing them.
	     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-group-exchange-sha1,
		   diffie-hellman-group14-sha1,
		   diffie-hellman-group1-sha1

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

     LocalCommand
	     Specifies a command to execute on the local machine after suc-
	     cessfully 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 must be [bind_address:]port and the
	     second argument must be host:hostport.  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 privi-
	     leged 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.

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

     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-sepa-
	     rated.  If the specified value begins with a `+' character, then
	     the specified algorithms will be appended to the default set
	     instead of replacing them.

	     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
	     This option can be used if the home directory is shared across
	     machines.	In this case localhost will refer to a different
	     machine on each of the machines and the user will get many warn-
	     ings about changed host keys.  However, this option disables host
	     authentication for localhost.  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).

     PKCS11Provider
	     Specifies which PKCS#11 provider to use.  The argument to this
	     keyword is the PKCS#11 shared library ssh(1) should use to commu-
	     nicate with a PKCS#11 token providing the user's private RSA key.

     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

     Protocol
	     Specifies the protocol versions ssh(1) should support in order of
	     preference.  The possible values are 1 and 2.  Multiple versions
	     must be comma-separated.  When this option is set to 2,1 ssh will
	     try version 2 and fall back to version 1 if version 2 is not
	     available.	 The default is version 2.  Protocol 1 suffers from a
	     number of cryptographic weaknesses and should not be used.	 It is
	     only offered to support legacy devices.

     ProxyCommand
	     Specifies the command to use to connect to the server.  The com-
	     mand 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 manage-
	     ment 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 [user@]host[:port].	Multi-
	     ple proxies may be separated by comma characters and will be vis-
	     ited sequentially.	 Setting this option will cause ssh(1) to con-
	     nect to the target host by first making a ssh(1) connection to
	     the specified ProxyJump host and then establishing a TCP forward-
	     ing to the ultimate target from there.

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

     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.

     PubkeyAcceptedKeyTypes
	     Specifies the key types that will be used for public key authen-
	     tication as a comma-separated pattern list.  Alternately if the
	     specified value begins with a `+' character, then the key types
	     after it will be appended to the default instead of replacing it.
	     The default for this option is:

		ecdsa-sha2-nistp256-cert-v01@openssh.com,
		ecdsa-sha2-nistp384-cert-v01@openssh.com,
		ecdsa-sha2-nistp521-cert-v01@openssh.com,
		ssh-ed25519-cert-v01@openssh.com,
		ssh-rsa-cert-v01@openssh.com,
		ssh-dss-cert-v01@openssh.com,
		ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
		ssh-ed25519,ssh-rsa,ssh-dsa

	     The list of available key types may also be obtained using "ssh
	     -Q key".

     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 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 docu-
	     mented 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.

     RemoteForward
	     Specifies that a TCP port on the remote machine be forwarded over
	     the secure channel to the specified host and port from the local
	     machine.  The first argument must be [bind_address:]port and the
	     second argument must be host:hostport.  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.

	     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 inter-
	     faces.  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 ses-
	     sion).  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).

     RhostsRSAAuthentication
	     Specifies whether to try rhosts based authentication with RSA
	     host authentication.  The argument must be yes or no (the
	     default).	This option applies to protocol version 1 only and
	     requires ssh(1) to be setuid root.

     RSAAuthentication
	     Specifies whether to try RSA authentication.  The argument to
	     this keyword must be yes (the default) or no.  RSA authentication
	     will only be attempted if the identity file exists, or an authen-
	     tication agent is running.	 Note that this option applies to pro-
	     tocol version 1 only.

     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 wild-
	     card characters.  Multiple environment variables may be separated
	     by whitespace or spread across multiple SendEnv directives.  The
	     default is not to send any environment variables.

	     See PATTERNS for more information on patterns.

     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 there-
	     fore will not be spoofable.  The TCP keepalive option enabled by
	     TCPKeepAlive is spoofable.	 The server alive mechanism is valu-
	     able when the client or server depend on knowing when a connec-
	     tion has become inactive.

	     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.

     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 pro-
	     tection against trojan horse 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 no, ssh will automatically add new host keys to the user
	     known hosts files.	 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.

     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 tempo-
	     rarily, 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.

     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 addi-
	     tional hostkeys from the server sent after authentication has
	     completed and add them to UserKnownHostsFile.  The argument must
	     be yes, no (the default) or ask.  Enabling 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.  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.

     UsePrivilegedPort
	     Specifies whether to use a privileged port for outgoing connec-
	     tions.  The argument must be yes or no (the default).  If set to
	     yes, ssh(1) must be setuid root.  Note that this option must be
	     set to yes for RhostsRSAAuthentication with older servers.

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

     UserKnownHostsFile
	     Specifies one or more files to use for the user host key data-
	     base, separated by whitespace.  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 finger-
	     print 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 decla-
     rations for any host in the ".co.uk" set of domains, the following pat-
     tern 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"

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

	   %%	 A literal `%'.
	   %C	 Shorthand for %l%h%p%r.
	   %d	 Local user's home directory.
	   %h	 The remote hostname.
	   %i	 The local user ID.
	   %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.
	   %u	 The local username.

     Match exec accepts the tokens %%, %h, %L, %l, %n, %p, %r, and %u.

     CertificateFile accepts the tokens %%, %d, %h, %l, %r, and %u.

     ControlPath accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and
     %u.

     HostName accepts the tokens %% and %h.

     IdentityAgent and IdentityFile accept the tokens %%, %d, %h, %l, %r, and
     %u.

     LocalCommand accepts the tokens %%, %C, %d, %h, %l, %n, %p, %r, and %u.

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

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 accessible by oth-
	     ers.

     /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 cre-
     ated OpenSSH.  Markus Friedl contributed the support for SSH protocol
     versions 1.5 and 2.0.

BSD			       November 23, 2024			   BSD