2 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
3 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 .\" All rights reserved
6 .\" As far as I am concerned, the code I have written for this software
7 .\" can be used freely for any purpose. Any derived versions of this
8 .\" software must be clearly marked as such, and if the derived work is
9 .\" incompatible with the protocol description in the RFC file, it must be
10 .\" called by a name other than "ssh" or "Secure Shell".
12 .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
13 .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
14 .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
16 .\" Redistribution and use in source and binary forms, with or without
17 .\" modification, are permitted provided that the following conditions
19 .\" 1. Redistributions of source code must retain the above copyright
20 .\" notice, this list of conditions and the following disclaimer.
21 .\" 2. Redistributions in binary form must reproduce the above copyright
22 .\" notice, this list of conditions and the following disclaimer in the
23 .\" documentation and/or other materials provided with the distribution.
25 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
26 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
28 .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
29 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
30 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
31 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
32 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
33 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
34 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 .\" $OpenBSD: ssh_config.5,v 1.374 2022/09/17 10:33:18 djm Exp $
37 .Dd $Mdocdate: September 17 2022 $
42 .Nd OpenSSH client configuration file
45 obtains configuration data from the following sources in
48 .Bl -enum -offset indent -compact
52 user's configuration file
55 system-wide configuration file
56 .Pq Pa /etc/ssh/ssh_config
59 For each parameter, the first obtained value
61 The configuration files contain sections separated by
63 specifications, and that section is only applied for hosts that
64 match one of the patterns given in the specification.
65 The matched host name is usually the one given on the command line
67 .Cm CanonicalizeHostname
68 option for exceptions).
70 Since the first obtained value for each parameter is used, more
71 host-specific declarations should be given near the beginning of the
72 file, and general defaults at the end.
74 The file contains keyword-argument pairs, one per line.
77 and empty lines are interpreted as comments.
78 Arguments may optionally be enclosed in double quotes
80 in order to represent arguments containing spaces.
81 Configuration options may be separated by whitespace or
82 optional whitespace and exactly one
84 the latter format is useful to avoid the need to quote whitespace
85 when specifying configuration options using the
94 keywords and their meanings are as follows (note that
95 keywords are case-insensitive and arguments are case-sensitive):
98 Restricts the following declarations (up to the next
102 keyword) to be only for those hosts that match one of the patterns
103 given after the keyword.
104 If more than one pattern is provided, they should be separated by whitespace.
107 as a pattern can be used to provide global
108 defaults for all hosts.
109 The host is usually the
111 argument given on the command line
113 .Cm CanonicalizeHostname
114 keyword for exceptions).
116 A pattern entry may be negated by prefixing it with an exclamation mark
118 If a negated entry is matched, then the
120 entry is ignored, regardless of whether any other patterns on the line
122 Negated matches are therefore useful to provide exceptions for wildcard
127 for more information on patterns.
129 Restricts the following declarations (up to the next
133 keyword) to be used only when the conditions following the
135 keyword are satisfied.
136 Match conditions are specified using one or more criteria
139 which always matches.
140 The available criteria keywords are:
151 criteria must appear alone or immediately after
155 Other criteria may be combined arbitrarily.
162 Criteria may be negated by prepending an exclamation mark
167 keyword matches only when the configuration file is being re-parsed
168 after hostname canonicalization (see the
169 .Cm CanonicalizeHostname
171 This may be useful to specify conditions that work with canonical host
176 keyword requests that the configuration be re-parsed (regardless of whether
177 .Cm CanonicalizeHostname
178 is enabled), and matches only during this final pass.
180 .Cm CanonicalizeHostname
185 match during the same pass.
189 keyword executes the specified command under the user's shell.
190 If the command returns a zero exit status then the condition is considered true.
191 Commands containing whitespace characters must be quoted.
194 accept the tokens described in the
198 The other keywords' criteria must be single entries or comma-separated
199 lists and may use the wildcard and negation operators described in the
204 keyword are matched against the target hostname, after any substitution
208 .Cm CanonicalizeHostname
212 keyword matches against the hostname as it was specified on the command-line.
215 keyword matches against the target username on the remote host.
218 keyword matches against the name of the local user running
220 (this keyword may be useful in system-wide
223 .It Cm AddKeysToAgent
224 Specifies whether keys should be automatically added to a running
226 If this option is set to
228 and a key is loaded from a file, the key and its passphrase are added to
229 the agent with the default lifetime, as if by
231 If this option is set to
234 will require confirmation using the
236 program before adding a key (see
239 If this option is set to
241 each use of the key must be confirmed, as if the
243 option was specified to
245 If this option is set to
247 no keys are added to the agent.
248 Alternately, this option may be specified as a time interval
249 using the format described in the
253 to specify the key's lifetime in
255 after which it will automatically be removed.
261 (optionally followed by a time interval),
265 Specifies which address family to use when connecting.
276 user interaction such as password prompts and host key confirmation requests
278 This option is useful in scripts and other batch jobs where no user
279 is present to interact with
287 Use the specified address on the local machine as the source address of
289 Only useful on systems with more than one address.
291 Use the address of the specified interface on the local machine as the
292 source address of the connection.
293 .It Cm CanonicalDomains
295 .Cm CanonicalizeHostname
296 is enabled, this option specifies the list of domain suffixes in which to
297 search for the specified destination host.
298 .It Cm CanonicalizeFallbackLocal
299 Specifies whether to fail with an error when hostname canonicalization fails.
302 will attempt to look up the unqualified hostname using the system resolver's
309 .Cm CanonicalizeHostname
310 is enabled and the target hostname cannot be found in any of the domains
312 .Cm CanonicalDomains .
313 .It Cm CanonicalizeHostname
314 Controls whether explicit hostname canonicalization is performed.
317 is not to perform any name rewriting and let the system resolver handle all
321 then, for connections that do not use a
326 will attempt to canonicalize the hostname specified on the command line
330 .Cm CanonicalizePermittedCNAMEs
333 .Cm CanonicalizeHostname
336 then canonicalization is applied to proxied connections too.
338 If this option is enabled, then the configuration files are processed
339 again using the new target name to pick up any new configuration in matching
346 disables the use of a
349 .It Cm CanonicalizeMaxDots
350 Specifies the maximum number of dot characters in a hostname before
351 canonicalization is disabled.
353 allows a single dot (i.e. hostname.subdomain).
354 .It Cm CanonicalizePermittedCNAMEs
355 Specifies rules to determine whether CNAMEs should be followed when
356 canonicalizing hostnames.
357 The rules consist of one or more arguments of
358 .Ar source_domain_list : Ns Ar target_domain_list ,
360 .Ar source_domain_list
361 is a pattern-list of domains that may follow CNAMEs in canonicalization,
363 .Ar target_domain_list
364 is a pattern-list of domains that they may resolve to.
367 .Qq *.a.example.com:*.b.example.com,*.c.example.com
368 will allow hostnames matching
370 to be canonicalized to names in the
378 causes no CNAMEs to be considered for canonicalization.
379 This is the default behaviour.
380 .It Cm CASignatureAlgorithms
381 Specifies which algorithms are allowed for signing of certificates
382 by certificate authorities (CAs).
384 .Bd -literal -offset indent
385 ssh-ed25519,ecdsa-sha2-nistp256,
386 ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
387 sk-ssh-ed25519@openssh.com,
388 sk-ecdsa-sha2-nistp256@openssh.com,
389 rsa-sha2-512,rsa-sha2-256
392 If the specified list begins with a
394 character, then the specified algorithms will be appended to the default set
395 instead of replacing them.
396 If the specified list begins with a
398 character, then the specified algorithms (including wildcards) will be removed
399 from the default set instead of replacing them.
402 will not accept host certificates signed using algorithms other than those
404 .It Cm CertificateFile
405 Specifies a file from which the user's certificate is read.
406 A corresponding private key must be provided separately in order
407 to use this certificate either
419 .Cm SecurityKeyProvider .
423 may use the tilde syntax to refer to a user's home directory,
424 the tokens described in the
426 section and environment variables as described in the
427 .Sx ENVIRONMENT VARIABLES
430 It is possible to have multiple certificate files specified in
431 configuration files; these certificates will be tried in sequence.
434 directives will add to the list of certificates used for
440 will additionally check the host IP address in the
443 This allows it to detect if a host key changed due to DNS spoofing
444 and will add addresses of destination hosts to
445 .Pa ~/.ssh/known_hosts
446 in the process, regardless of the setting of
447 .Cm StrictHostKeyChecking .
448 If the option is set to
451 the check will not be executed.
455 Specifies the ciphers allowed and their order of preference.
456 Multiple ciphers must be comma-separated.
457 If the specified list begins with a
459 character, then the specified ciphers will be appended to the default set
460 instead of replacing them.
461 If the specified list begins with a
463 character, then the specified ciphers (including wildcards) will be removed
464 from the default set instead of replacing them.
465 If the specified list begins with a
467 character, then the specified ciphers will be placed at the head of the
470 The supported ciphers are:
471 .Bd -literal -offset indent
479 aes128-gcm@openssh.com
480 aes256-gcm@openssh.com
481 chacha20-poly1305@openssh.com
485 .Bd -literal -offset indent
486 chacha20-poly1305@openssh.com,
487 aes128-ctr,aes192-ctr,aes256-ctr,
488 aes128-gcm@openssh.com,aes256-gcm@openssh.com
491 The list of available ciphers may also be obtained using
493 .It Cm ClearAllForwardings
494 Specifies that all local, remote, and dynamic port forwardings
495 specified in the configuration files or on the command line be
497 This option is primarily useful when used from the
499 command line to clear port forwardings set in
500 configuration files, and is automatically set by
510 Specifies whether to use compression.
516 .It Cm ConnectionAttempts
517 Specifies the number of tries (one per second) to make before exiting.
518 The argument must be an integer.
519 This may be useful in scripts if the connection sometimes fails.
521 .It Cm ConnectTimeout
522 Specifies the timeout (in seconds) used when connecting to the
523 SSH server, instead of using the default system TCP timeout.
524 This timeout is applied both to establishing the connection and to performing
525 the initial SSH protocol handshake and key exchange.
527 Enables the sharing of multiple sessions over a single network connection.
531 will listen for connections on a control socket specified using the
534 Additional sessions can connect to this socket using the same
541 These sessions will try to reuse the master instance's network connection
542 rather than initiating new ones, but will fall back to connecting normally
543 if the control socket does not exist, or is not listening.
549 to listen for control connections, but require confirmation using
555 will continue without connecting to a master instance.
559 forwarding is supported over these multiplexed connections, however the
560 display and agent forwarded will be the one belonging to the master
561 connection i.e. it is not possible to forward multiple displays or agents.
563 Two additional options allow for opportunistic multiplexing: try to use a
564 master connection but fall back to creating a new one if one does not already
570 The latter requires confirmation like the
574 Specify the path to the control socket used for connection sharing as described
577 section above or the string
579 to disable connection sharing.
582 may use the tilde syntax to refer to a user's home directory,
583 the tokens described in the
585 section and environment variables as described in the
586 .Sx ENVIRONMENT VARIABLES
588 It is recommended that any
590 used for opportunistic connection sharing include
591 at least %h, %p, and %r (or alternatively %C) and be placed in a directory
592 that is not writable by other users.
593 This ensures that shared connections are uniquely identified.
594 .It Cm ControlPersist
595 When used in conjunction with
597 specifies that the master connection should remain open
598 in the background (waiting for future client connections)
599 after the initial client connection has been closed.
603 then the master connection will not be placed into the background,
604 and will close as soon as the initial client connection is closed.
608 then the master connection will remain in the background indefinitely
609 (until killed or closed via a mechanism such as the
611 If set to a time in seconds, or a time in any of the formats documented in
613 then the backgrounded master connection will automatically terminate
614 after it has remained idle (with no client connections) for the
616 .It Cm DynamicForward
617 Specifies that a TCP port on the local machine be forwarded
618 over the secure channel, and the application
619 protocol is then used to determine where to connect to from the
624 .Oo Ar bind_address : Oc Ar port .
626 IPv6 addresses can be specified by enclosing addresses in square brackets.
627 By default, the local port is bound in accordance with the
632 may be used to bind the connection to a specific address.
637 indicates that the listening port be bound for local use only, while an
640 indicates that the port should be available from all interfaces.
642 Currently the SOCKS4 and SOCKS5 protocols are supported, and
644 will act as a SOCKS server.
645 Multiple forwardings may be specified, and
646 additional forwardings can be given on the command line.
647 Only the superuser can forward privileged ports.
648 .It Cm EnableSSHKeysign
649 Setting this option to
651 in the global client configuration file
652 .Pa /etc/ssh/ssh_config
653 enables the use of the helper program
656 .Cm HostbasedAuthentication .
662 This option should be placed in the non-hostspecific section.
665 for more information.
667 Sets the escape character (default:
669 The escape character can also
670 be set on the command line.
671 The argument should be a single character,
673 followed by a letter, or
675 to disable the escape
676 character entirely (making the connection transparent for binary
678 .It Cm ExitOnForwardFailure
681 should terminate the connection if it cannot set up all requested
682 dynamic, tunnel, local, and remote port forwardings, (e.g.\&
683 if either end is unable to bind and listen on a specified port).
685 .Cm ExitOnForwardFailure
686 does not apply to connections made over port forwardings and will not,
689 to exit if TCP connections to the ultimate forwarding destination fail.
695 .It Cm FingerprintHash
696 Specifies the hash algorithm used when displaying key fingerprints.
702 .It Cm ForkAfterAuthentication
705 to go to background just before command execution.
708 is going to ask for passwords or passphrases, but the user
709 wants it in the background.
712 configuration option being set to
714 The recommended way to start X11 programs at a remote site is with
716 .Ic ssh -f host xterm ,
720 .Cm ForkAfterAuthentication
721 configuration option is set to
725 .Cm ExitOnForwardFailure
726 configuration option is set to
728 then a client started with the
729 .Cm ForkAfterAuthentication
730 configuration option being set to
732 will wait for all remote port forwards to be successfully established
733 before placing itself in the background.
734 The argument to this keyword must be
742 Specifies whether the connection to the authentication agent (if any)
743 will be forwarded to the remote machine.
748 an explicit path to an agent socket or the name of an environment variable
751 in which to find the path.
753 Agent forwarding should be enabled with caution.
754 Users with the ability to bypass file permissions on the remote host
755 (for the agent's Unix-domain socket)
756 can access the local agent through the forwarded connection.
757 An attacker cannot obtain key material from the agent,
758 however they can perform operations on the keys that enable them to
759 authenticate using the identities loaded into the agent.
761 Specifies whether X11 connections will be automatically redirected
762 over the secure channel and
771 X11 forwarding should be enabled with caution.
772 Users with the ability to bypass file permissions on the remote host
773 (for the user's X11 authorization database)
774 can access the local X11 display through the forwarded connection.
775 An attacker may then be able to perform activities such as keystroke monitoring
777 .Cm ForwardX11Trusted
778 option is also enabled.
779 .It Cm ForwardX11Timeout
780 Specify a timeout for untrusted X11 forwarding
781 using the format described in the
785 X11 connections received by
787 after this time will be refused.
789 .Cm ForwardX11Timeout
790 to zero will disable the timeout and permit X11 forwarding for the life
792 The default is to disable untrusted X11 forwarding after twenty minutes has
794 .It Cm ForwardX11Trusted
795 If this option is set to
797 remote X11 clients will have full access to the original X11 display.
799 If this option is set to
802 remote X11 clients will be considered untrusted and prevented
803 from stealing or tampering with data belonging to trusted X11
807 token used for the session will be set to expire after 20 minutes.
808 Remote clients will be refused access after this time.
810 See the X11 SECURITY extension specification for full details on
811 the restrictions imposed on untrusted clients.
813 Specifies whether remote hosts are allowed to connect to local
817 binds local port forwardings to the loopback address.
818 This prevents other remote hosts from connecting to forwarded ports.
820 can be used to specify that ssh
821 should bind local port forwardings to the wildcard address,
822 thus allowing remote hosts to connect to forwarded ports.
828 .It Cm GlobalKnownHostsFile
829 Specifies one or more files to use for the global
830 host key database, separated by whitespace.
832 .Pa /etc/ssh/ssh_known_hosts ,
833 .Pa /etc/ssh/ssh_known_hosts2 .
834 .It Cm GSSAPIAuthentication
835 Specifies whether user authentication based on GSSAPI is allowed.
838 .It Cm GSSAPIDelegateCredentials
839 Forward (delegate) credentials to the server.
842 .It Cm HashKnownHosts
845 should hash host names and addresses when they are added to
846 .Pa ~/.ssh/known_hosts .
847 These hashed names may be used normally by
851 but they do not visually reveal identifying information if the
852 file's contents are disclosed.
855 Note that existing names and addresses in known hosts files
856 will not be converted automatically,
857 but may be manually hashed using
859 .It Cm HostbasedAcceptedAlgorithms
860 Specifies the signature algorithms that will be used for hostbased
861 authentication as a comma-separated list of patterns.
862 Alternately if the specified list begins with a
864 character, then the specified signature algorithms will be appended
865 to the default set instead of replacing them.
866 If the specified list begins with a
868 character, then the specified signature algorithms (including wildcards)
869 will be removed from the default set instead of replacing them.
870 If the specified list begins with a
872 character, then the specified signature algorithms will be placed
873 at the head of the default set.
874 The default for this option is:
875 .Bd -literal -offset 3n
876 ssh-ed25519-cert-v01@openssh.com,
877 ecdsa-sha2-nistp256-cert-v01@openssh.com,
878 ecdsa-sha2-nistp384-cert-v01@openssh.com,
879 ecdsa-sha2-nistp521-cert-v01@openssh.com,
880 sk-ssh-ed25519-cert-v01@openssh.com,
881 sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
882 rsa-sha2-512-cert-v01@openssh.com,
883 rsa-sha2-256-cert-v01@openssh.com,
885 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
886 sk-ssh-ed25519@openssh.com,
887 sk-ecdsa-sha2-nistp256@openssh.com,
888 rsa-sha2-512,rsa-sha2-256
895 may be used to list supported signature algorithms.
896 This was formerly named HostbasedKeyTypes.
897 .It Cm HostbasedAuthentication
898 Specifies whether to try rhosts based authentication with public key
905 .It Cm HostKeyAlgorithms
906 Specifies the host key signature algorithms
907 that the client wants to use in order of preference.
908 Alternately if the specified list begins with a
910 character, then the specified signature algorithms will be appended to
911 the default set instead of replacing them.
912 If the specified list begins with a
914 character, then the specified signature algorithms (including wildcards)
915 will be removed from the default set instead of replacing them.
916 If the specified list begins with a
918 character, then the specified signature algorithms will be placed
919 at the head of the default set.
920 The default for this option is:
921 .Bd -literal -offset 3n
922 ssh-ed25519-cert-v01@openssh.com,
923 ecdsa-sha2-nistp256-cert-v01@openssh.com,
924 ecdsa-sha2-nistp384-cert-v01@openssh.com,
925 ecdsa-sha2-nistp521-cert-v01@openssh.com,
926 sk-ssh-ed25519-cert-v01@openssh.com,
927 sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
928 rsa-sha2-512-cert-v01@openssh.com,
929 rsa-sha2-256-cert-v01@openssh.com,
931 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
932 sk-ecdsa-sha2-nistp256@openssh.com,
933 sk-ssh-ed25519@openssh.com,
934 rsa-sha2-512,rsa-sha2-256
937 If hostkeys are known for the destination host then this default is modified
938 to prefer their algorithms.
940 The list of available signature algorithms may also be obtained using
941 .Qq ssh -Q HostKeyAlgorithms .
943 Specifies an alias that should be used instead of the
944 real host name when looking up or saving the host key
945 in the host key database files and when validating host certificates.
946 This option is useful for tunneling SSH connections
947 or for multiple servers running on a single host.
949 Specifies the real host name to log into.
950 This can be used to specify nicknames or abbreviations for hosts.
953 accept the tokens described in the
956 Numeric IP addresses are also permitted (both on the command line and in
959 The default is the name given on the command line.
960 .It Cm IdentitiesOnly
963 should only use the configured authentication identity and certificate files
964 (either the default files, or those explicitly configured in the
975 .Cm SecurityKeyProvider
976 offers more identities.
977 The argument to this keyword must be
982 This option is intended for situations where ssh-agent
983 offers many different identities.
987 socket used to communicate with the authentication agent.
989 This option overrides the
991 environment variable and can be used to select a specific agent.
992 Setting the socket name to
994 disables the use of an authentication agent.
997 is specified, the location of the socket will be read from the
999 environment variable.
1000 Otherwise if the specified value begins with a
1002 character, then it will be treated as an environment variable containing
1003 the location of the socket.
1007 may use the tilde syntax to refer to a user's home directory,
1008 the tokens described in the
1010 section and environment variables as described in the
1011 .Sx ENVIRONMENT VARIABLES
1014 Specifies a file from which the user's DSA, ECDSA, authenticator-hosted ECDSA,
1015 Ed25519, authenticator-hosted Ed25519 or RSA authentication identity is read.
1018 .Pa ~/.ssh/id_ecdsa ,
1019 .Pa ~/.ssh/id_ecdsa_sk ,
1020 .Pa ~/.ssh/id_ed25519 ,
1021 .Pa ~/.ssh/id_ed25519_sk
1024 Additionally, any identities represented by the authentication agent
1025 will be used for authentication unless
1028 If no certificates have been explicitly specified by
1029 .Cm CertificateFile ,
1031 will try to load certificate information from the filename obtained by
1034 to the path of a specified
1039 may use the tilde syntax to refer to a user's home directory
1040 or the tokens described in the
1044 It is possible to have
1045 multiple identity files specified in configuration files; all these
1046 identities will be tried in sequence.
1049 directives will add to the list of identities tried (this behaviour
1050 differs from that of other configuration directives).
1053 may be used in conjunction with
1055 to select which identities in an agent are offered during authentication.
1057 may also be used in conjunction with
1059 in order to provide any certificate also needed for authentication with
1061 .It Cm IgnoreUnknown
1062 Specifies a pattern-list of unknown options to be ignored if they are
1063 encountered in configuration parsing.
1064 This may be used to suppress errors if
1066 contains options that are unrecognised by
1068 It is recommended that
1070 be listed early in the configuration file as it will not be applied
1071 to unknown options that appear before it.
1073 Include the specified configuration file(s).
1074 Multiple pathnames may be specified and each pathname may contain
1076 wildcards and, for user configurations, shell-like
1078 references to user home directories.
1079 Wildcards will be expanded and processed in lexical order.
1080 Files without absolute paths are assumed to be in
1082 if included in a user configuration file or
1084 if included from the system configuration file.
1086 directive may appear inside a
1091 to perform conditional inclusion.
1093 Specifies the IPv4 type-of-service or DSCP class for connections.
1122 to use the operating system default.
1123 This option may take one or two arguments, separated by whitespace.
1124 If one argument is specified, it is used as the packet class unconditionally.
1125 If two values are specified, the first is automatically selected for
1126 interactive sessions and the second for non-interactive sessions.
1130 for interactive sessions and
1133 for non-interactive sessions.
1134 .It Cm KbdInteractiveAuthentication
1135 Specifies whether to use keyboard-interactive authentication.
1136 The argument to this keyword must be
1141 .Cm ChallengeResponseAuthentication
1142 is a deprecated alias for this.
1143 .It Cm KbdInteractiveDevices
1144 Specifies the list of methods to use in keyboard-interactive authentication.
1145 Multiple method names must be comma-separated.
1146 The default is to use the server specified list.
1147 The methods available vary depending on what the server supports.
1148 For an OpenSSH server,
1149 it may be zero or more of:
1153 .It Cm KexAlgorithms
1154 Specifies the available KEX (Key Exchange) algorithms.
1155 Multiple algorithms must be comma-separated.
1156 If the specified list begins with a
1158 character, then the specified algorithms will be appended to the default set
1159 instead of replacing them.
1160 If the specified list begins with a
1162 character, then the specified algorithms (including wildcards) will be removed
1163 from the default set instead of replacing them.
1164 If the specified list begins with a
1166 character, then the specified algorithms will be placed at the head of the
1169 .Bd -literal -offset indent
1170 sntrup761x25519-sha512@openssh.com,
1171 curve25519-sha256,curve25519-sha256@libssh.org,
1172 ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
1173 diffie-hellman-group-exchange-sha256,
1174 diffie-hellman-group16-sha512,
1175 diffie-hellman-group18-sha512,
1176 diffie-hellman-group14-sha256
1179 The list of available key exchange algorithms may also be obtained using
1181 .It Cm KnownHostsCommand
1182 Specifies a command to use to obtain a list of host keys, in addition to
1184 .Cm UserKnownHostsFile
1186 .Cm GlobalKnownHostsFile .
1187 This command is executed after the files have been read.
1188 It may write host key lines to standard output in identical format to the
1189 usual files (described in the
1190 .Sx VERIFYING HOST KEYS
1194 .Cm KnownHostsCommand
1195 accept the tokens described in the
1198 The command may be invoked multiple times per connection: once when preparing
1199 the preference list of host key algorithms to use, again to obtain the
1200 host key for the requested host name and, if
1202 is enabled, one more time to obtain the host key matching the server's
1204 If the command exits abnormally or returns a non-zero exit status then the
1205 connection is terminated.
1207 Specifies a command to execute on the local machine after successfully
1208 connecting to the server.
1209 The command string extends to the end of the line, and is executed with
1213 accept the tokens described in the
1217 The command is run synchronously and does not have access to the
1221 It should not be used for interactive commands.
1223 This directive is ignored unless
1224 .Cm PermitLocalCommand
1227 Specifies that a TCP port on the local machine be forwarded over
1228 the secure channel to the specified host and port from the remote machine.
1229 The first argument specifies the listener and may be
1231 .Oo Ar bind_address : Oc Ar port
1233 or a Unix domain socket path.
1234 The second argument is the destination and may be
1235 .Ar host : Ns Ar hostport
1236 or a Unix domain socket path if the remote host supports it.
1238 IPv6 addresses can be specified by enclosing addresses in square brackets.
1239 Multiple forwardings may be specified, and additional forwardings can be
1240 given on the command line.
1241 Only the superuser can forward privileged ports.
1242 By default, the local port is bound in accordance with the
1245 However, an explicit
1247 may be used to bind the connection to a specific address.
1252 indicates that the listening port be bound for local use only, while an
1255 indicates that the port should be available from all interfaces.
1256 Unix domain socket paths may use the tokens described in the
1258 section and environment variables as described in the
1259 .Sx ENVIRONMENT VARIABLES
1262 Gives the verbosity level that is used when logging messages from
1264 The possible values are:
1265 QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
1266 The default is INFO.
1267 DEBUG and DEBUG1 are equivalent.
1268 DEBUG2 and DEBUG3 each specify higher levels of verbose output.
1270 Specify one or more overrides to LogLevel.
1271 An override consists of a pattern lists that matches the source file, function
1272 and line number to force detailed logging for.
1273 For example, an override pattern of:
1274 .Bd -literal -offset indent
1275 kex.c:*:1000,*:kex_exchange_identification():*,packet.c:*
1278 would enable detailed logging for line 1000 of
1281 .Fn kex_exchange_identification
1282 function, and all code in the
1285 This option is intended for debugging and no overrides are enabled by default.
1287 Specifies the MAC (message authentication code) algorithms
1288 in order of preference.
1289 The MAC algorithm is used for data integrity protection.
1290 Multiple algorithms must be comma-separated.
1291 If the specified list begins with a
1293 character, then the specified algorithms will be appended to the default set
1294 instead of replacing them.
1295 If the specified list begins with a
1297 character, then the specified algorithms (including wildcards) will be removed
1298 from the default set instead of replacing them.
1299 If the specified list begins with a
1301 character, then the specified algorithms will be placed at the head of the
1304 The algorithms that contain
1306 calculate the MAC after encryption (encrypt-then-mac).
1307 These are considered safer and their use recommended.
1310 .Bd -literal -offset indent
1311 umac-64-etm@openssh.com,umac-128-etm@openssh.com,
1312 hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,
1313 hmac-sha1-etm@openssh.com,
1314 umac-64@openssh.com,umac-128@openssh.com,
1315 hmac-sha2-256,hmac-sha2-512,hmac-sha1
1318 The list of available MAC algorithms may also be obtained using
1320 .It Cm NoHostAuthenticationForLocalhost
1321 Disable host authentication for localhost (loopback addresses).
1322 The argument to this keyword must be
1327 .It Cm NumberOfPasswordPrompts
1328 Specifies the number of password prompts before giving up.
1329 The argument to this keyword must be an integer.
1331 .It Cm PasswordAuthentication
1332 Specifies whether to use password authentication.
1333 The argument to this keyword must be
1338 .It Cm PermitLocalCommand
1339 Allow local command execution via the
1342 .Ic !\& Ns Ar command
1345 The argument must be
1350 .It Cm PermitRemoteOpen
1351 Specifies the destinations to which remote TCP port forwarding is permitted when
1353 is used as a SOCKS proxy.
1354 The forwarding specification must be one of the following forms:
1356 .Bl -item -offset indent -compact
1358 .Cm PermitRemoteOpen
1363 .Cm PermitRemoteOpen
1365 .Ar IPv4_addr : port
1368 .Cm PermitRemoteOpen
1370 .Ar \&[ IPv6_addr \&] : port
1374 Multiple forwards may be specified by separating them with whitespace.
1377 can be used to remove all restrictions and permit any forwarding requests.
1380 can be used to prohibit all forwarding requests.
1383 can be used for host or port to allow all hosts or ports respectively.
1384 Otherwise, no pattern matching or address lookups are performed on supplied
1386 .It Cm PKCS11Provider
1387 Specifies which PKCS#11 provider to use or
1389 to indicate that no provider should be used (the default).
1390 The argument to this keyword is a path to the PKCS#11 shared library
1392 should use to communicate with a PKCS#11 token providing keys for user
1395 Specifies the port number to connect on the remote host.
1397 .It Cm PreferredAuthentications
1398 Specifies the order in which the client should try authentication methods.
1399 This allows a client to prefer one method (e.g.\&
1400 .Cm keyboard-interactive )
1401 over another method (e.g.\&
1404 .Bd -literal -offset indent
1405 gssapi-with-mic,hostbased,publickey,
1406 keyboard-interactive,password
1409 Specifies the command to use to connect to the server.
1411 string extends to the end of the line, and is executed
1412 using the user's shell
1414 directive to avoid a lingering shell process.
1418 accept the tokens described in the
1421 The command can be basically anything,
1422 and should read from its standard input and write to its standard output.
1423 It should eventually connect an
1425 server running on some machine, or execute
1428 Host key management will be done using the
1430 of the host being connected (defaulting to the name typed by the user).
1431 Setting the command to
1433 disables this option entirely.
1436 is not available for connects with a proxy command.
1438 This directive is useful in conjunction with
1440 and its proxy support.
1441 For example, the following directive would connect via an HTTP proxy at
1443 .Bd -literal -offset 3n
1444 ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
1447 Specifies one or more jump proxies as either
1456 Multiple proxies may be separated by comma characters and will be visited
1458 Setting this option will cause
1460 to connect to the target host by first making a
1462 connection to the specified
1464 host and then establishing a
1465 TCP forwarding to the ultimate target from there.
1468 disables this option entirely.
1470 Note that this option will compete with the
1472 option - whichever is specified first will prevent later instances of the
1473 other from taking effect.
1475 Note also that the configuration for the destination host (either supplied
1476 via the command-line or the configuration file) is not generally applied
1479 should be used if specific configuration is required for jump hosts.
1480 .It Cm ProxyUseFdpass
1483 will pass a connected file descriptor back to
1485 instead of continuing to execute and pass data.
1488 .It Cm PubkeyAcceptedAlgorithms
1489 Specifies the signature algorithms that will be used for public key
1490 authentication as a comma-separated list of patterns.
1491 If the specified list begins with a
1493 character, then the algorithms after it will be appended to the default
1494 instead of replacing it.
1495 If the specified list begins with a
1497 character, then the specified algorithms (including wildcards) will be removed
1498 from the default set instead of replacing them.
1499 If the specified list begins with a
1501 character, then the specified algorithms will be placed at the head of the
1503 The default for this option is:
1504 .Bd -literal -offset 3n
1505 ssh-ed25519-cert-v01@openssh.com,
1506 ecdsa-sha2-nistp256-cert-v01@openssh.com,
1507 ecdsa-sha2-nistp384-cert-v01@openssh.com,
1508 ecdsa-sha2-nistp521-cert-v01@openssh.com,
1509 sk-ssh-ed25519-cert-v01@openssh.com,
1510 sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
1511 rsa-sha2-512-cert-v01@openssh.com,
1512 rsa-sha2-256-cert-v01@openssh.com,
1514 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
1515 sk-ssh-ed25519@openssh.com,
1516 sk-ecdsa-sha2-nistp256@openssh.com,
1517 rsa-sha2-512,rsa-sha2-256
1520 The list of available signature algorithms may also be obtained using
1521 .Qq ssh -Q PubkeyAcceptedAlgorithms .
1522 .It Cm PubkeyAuthentication
1523 Specifies whether to try public key authentication.
1524 The argument to this keyword must be
1531 The final two options enable public key authentication while respectively
1532 disabling or enabling the OpenSSH host-bound authentication protocol
1533 extension required for restricted
1537 Specifies the maximum amount of data that may be transmitted or received
1538 before the session key is renegotiated, optionally followed by a maximum
1539 amount of time that may pass before the session key is renegotiated.
1540 The first argument is specified in bytes and may have a suffix of
1545 to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
1546 The default is between
1550 depending on the cipher.
1551 The optional second value is specified in seconds and may use any of the
1552 units documented in the TIME FORMATS section of
1554 The default value for
1558 which means that rekeying is performed after the cipher's default amount
1559 of data has been sent or received and no time based rekeying is done.
1560 .It Cm RemoteCommand
1561 Specifies a command to execute on the remote machine after successfully
1562 connecting to the server.
1563 The command string extends to the end of the line, and is executed with
1567 accept the tokens described in the
1570 .It Cm RemoteForward
1571 Specifies that a TCP port on the remote machine be forwarded over
1573 The remote port may either be forwarded to a specified host and port
1574 from the local machine, or may act as a SOCKS 4/5 proxy that allows a remote
1575 client to connect to arbitrary destinations from the local machine.
1576 The first argument is the listening specification and may be
1578 .Oo Ar bind_address : Oc Ar port
1580 or, if the remote host supports it, a Unix domain socket path.
1581 If forwarding to a specific destination then the second argument must be
1582 .Ar host : Ns Ar hostport
1583 or a Unix domain socket path,
1584 otherwise if no destination argument is specified then the remote forwarding
1585 will be established as a SOCKS proxy.
1586 When acting as a SOCKS proxy, the destination of the connection can be
1588 .Cm PermitRemoteOpen .
1590 IPv6 addresses can be specified by enclosing addresses in square brackets.
1591 Multiple forwardings may be specified, and additional
1592 forwardings can be given on the command line.
1593 Privileged ports can be forwarded only when
1594 logging in as root on the remote machine.
1595 Unix domain socket paths may use the tokens described in the
1597 section and environment variables as described in the
1598 .Sx ENVIRONMENT VARIABLES
1604 the listen port will be dynamically allocated on the server and reported
1605 to the client at run time.
1609 is not specified, the default is to only bind to loopback addresses.
1614 or an empty string, then the forwarding is requested to listen on all
1618 will only succeed if the server's
1620 option is enabled (see
1621 .Xr sshd_config 5 ) .
1623 Specifies whether to request a pseudo-tty for the session.
1624 The argument may be one of:
1626 (never request a TTY),
1628 (always request a TTY when standard input is a TTY),
1630 (always request a TTY) or
1632 (request a TTY when opening a login session).
1633 This option mirrors the
1639 .It Cm RequiredRSASize
1640 Specifies the minimum RSA key size (in bits) that
1643 User authentication keys smaller than this limit will be ignored.
1644 Servers that present host keys smaller than this limit will cause the
1645 connection to be terminated.
1649 Note that this limit may only be raised from the default.
1650 .It Cm RevokedHostKeys
1651 Specifies revoked host public keys.
1652 Keys listed in this file will be refused for host authentication.
1653 Note that if this file does not exist or is not readable,
1654 then host authentication will be refused for all hosts.
1655 Keys may be specified as a text file, listing one public key per line, or as
1656 an OpenSSH Key Revocation List (KRL) as generated by
1658 For more information on KRLs, see the KEY REVOCATION LISTS section in
1660 .It Cm SecurityKeyProvider
1661 Specifies a path to a library that will be used when loading any
1662 FIDO authenticator-hosted keys, overriding the default of using
1663 the built-in USB HID support.
1665 If the specified value begins with a
1667 character, then it will be treated as an environment variable containing
1668 the path to the library.
1670 Specifies what variables from the local
1672 should be sent to the server.
1673 The server must also support it, and the server must be configured to
1674 accept these environment variables.
1677 environment variable is always sent whenever a
1678 pseudo-terminal is requested as it is required by the protocol.
1683 for how to configure the server.
1684 Variables are specified by name, which may contain wildcard characters.
1685 Multiple environment variables may be separated by whitespace or spread
1692 for more information on patterns.
1694 It is possible to clear previously set
1696 variable names by prefixing patterns with
1698 The default is not to send any environment variables.
1699 .It Cm ServerAliveCountMax
1700 Sets the number of server alive messages (see below) which may be
1703 receiving any messages back from the server.
1704 If this threshold is reached while server alive messages are being sent,
1705 ssh will disconnect from the server, terminating the session.
1706 It is important to note that the use of server alive messages is very
1710 The server alive messages are sent through the encrypted channel
1711 and therefore will not be spoofable.
1712 The TCP keepalive option enabled by
1715 The server alive mechanism is valuable when the client or
1716 server depend on knowing when a connection has become unresponsive.
1718 The default value is 3.
1720 .Cm ServerAliveInterval
1721 (see below) is set to 15 and
1722 .Cm ServerAliveCountMax
1723 is left at the default, if the server becomes unresponsive,
1724 ssh will disconnect after approximately 45 seconds.
1725 .It Cm ServerAliveInterval
1726 Sets a timeout interval in seconds after which if no data has been received
1729 will send a message through the encrypted
1730 channel to request a response from the server.
1732 is 0, indicating that these messages will not be sent to the server.
1734 May be used to either request invocation of a subsystem on the remote system,
1735 or to prevent the execution of a remote command at all.
1736 The latter is useful for just forwarding ports.
1737 The argument to this keyword must be
1747 (shell or command execution).
1749 Directly specify one or more environment variables and their contents to
1750 be sent to the server.
1753 with the exception of the
1755 variable, the server must be prepared to accept the environment variable.
1757 Redirects stdin from
1759 (actually, prevents reading from stdin).
1760 Either this or the equivalent
1762 option must be used when
1764 is run in the background.
1765 The argument to this keyword must be
1772 .It Cm StreamLocalBindMask
1773 Sets the octal file creation mode mask
1775 used when creating a Unix-domain socket file for local or remote
1777 This option is only used for port forwarding to a Unix-domain socket file.
1779 The default value is 0177, which creates a Unix-domain socket file that is
1780 readable and writable only by the owner.
1781 Note that not all operating systems honor the file mode on Unix-domain
1783 .It Cm StreamLocalBindUnlink
1784 Specifies whether to remove an existing Unix-domain socket file for local
1785 or remote port forwarding before creating a new one.
1786 If the socket file already exists and
1787 .Cm StreamLocalBindUnlink
1790 will be unable to forward the port to the Unix-domain socket file.
1791 This option is only used for port forwarding to a Unix-domain socket file.
1793 The argument must be
1798 .It Cm StrictHostKeyChecking
1799 If this flag is set to
1802 will never automatically add host keys to the
1803 .Pa ~/.ssh/known_hosts
1804 file, and refuses to connect to hosts whose host key has changed.
1805 This provides maximum protection against man-in-the-middle (MITM) attacks,
1806 though it can be annoying when the
1807 .Pa /etc/ssh/ssh_known_hosts
1808 file is poorly maintained or when connections to new hosts are
1810 This option forces the user to manually
1813 If this flag is set to
1815 then ssh will automatically add new host keys to the user's
1817 file, but will not permit connections to hosts with
1819 If this flag is set to
1823 ssh will automatically add new host keys to the user known hosts files
1824 and allow connections to hosts with changed hostkeys to proceed,
1825 subject to some restrictions.
1826 If this flag is set to
1830 will be added to the user known host files only after the user
1831 has confirmed that is what they really want to do, and
1832 ssh will refuse to connect to hosts whose host key has changed.
1834 known hosts will be verified automatically in all cases.
1835 .It Cm SyslogFacility
1836 Gives the facility code that is used when logging messages from
1838 The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
1839 LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1840 The default is USER.
1842 Specifies whether the system should send TCP keepalive messages to the
1844 If they are sent, death of the connection or crash of one
1845 of the machines will be properly noticed.
1846 However, this means that
1847 connections will die if the route is down temporarily, and some people
1852 (to send TCP keepalive messages), and the client will notice
1853 if the network goes down or the remote host dies.
1854 This is important in scripts, and many users want it too.
1856 To disable TCP keepalive messages, the value should be set to
1859 .Cm ServerAliveInterval
1860 for protocol-level keepalives.
1864 device forwarding between the client and the server.
1865 The argument must be
1876 requests the default tunnel mode, which is
1877 .Cm point-to-point .
1881 devices to open on the client
1886 The argument must be
1888 .Ar local_tun Op : Ar remote_tun .
1890 The devices may be specified by numerical ID or the keyword
1892 which uses the next available tunnel device.
1895 is not specified, it defaults to
1899 .It Cm UpdateHostKeys
1902 should accept notifications of additional hostkeys from the server sent
1903 after authentication has completed and add them to
1904 .Cm UserKnownHostsFile .
1905 The argument must be
1910 This option allows learning alternate hostkeys for a server
1911 and supports graceful key rotation by allowing a server to send replacement
1912 public keys before old ones are removed.
1914 Additional hostkeys are only accepted if the key used to authenticate the
1915 host was already trusted or explicitly accepted by the user, the host was
1917 .Cm UserKnownHostsFile
1919 .Cm GlobalKnownHostsFile )
1920 and the host was authenticated using a plain key and not a certificate.
1923 is enabled by default if the user has not overridden the default
1924 .Cm UserKnownHostsFile
1925 setting and has not enabled
1926 .Cm VerifyHostKeyDNS ,
1936 then the user is asked to confirm the modifications to the known_hosts file.
1937 Confirmation is currently incompatible with
1938 .Cm ControlPersist ,
1939 and will be disabled if it is enabled.
1943 from OpenSSH 6.8 and greater support the
1944 .Qq hostkeys@openssh.com
1945 protocol extension used to inform the client of all the server's hostkeys.
1947 Specifies the user to log in as.
1948 This can be useful when a different user name is used on different machines.
1949 This saves the trouble of
1950 having to remember to give the user name on the command line.
1951 .It Cm UserKnownHostsFile
1952 Specifies one or more files to use for the user
1953 host key database, separated by whitespace.
1954 Each filename may use tilde notation to refer to the user's home directory,
1955 the tokens described in the
1957 section and environment variables as described in the
1958 .Sx ENVIRONMENT VARIABLES
1961 .Pa ~/.ssh/known_hosts ,
1962 .Pa ~/.ssh/known_hosts2 .
1963 .It Cm VerifyHostKeyDNS
1964 Specifies whether to verify the remote key using DNS and SSHFP resource
1966 If this option is set to
1968 the client will implicitly trust keys that match a secure fingerprint
1970 Insecure fingerprints will be handled as if this option was set to
1972 If this option is set to
1974 information on fingerprint match will be displayed, but the user will still
1975 need to confirm new host keys according to the
1976 .Cm StrictHostKeyChecking
1980 if compiled with LDNS and
1985 .Sx VERIFYING HOST KEYS
1988 .It Cm VisualHostKey
1989 If this flag is set to
1991 an ASCII art representation of the remote host key fingerprint is
1992 printed in addition to the fingerprint string at login and
1993 for unknown host keys.
1994 If this flag is set to
1997 no fingerprint strings are printed at login and
1998 only the fingerprint string will be printed for unknown host keys.
1999 .It Cm XAuthLocation
2000 Specifies the full pathname of the
2004 .Pa /usr/local/bin/xauth .
2009 consists of zero or more non-whitespace characters,
2011 (a wildcard that matches zero or more characters),
2014 (a wildcard that matches exactly one character).
2015 For example, to specify a set of declarations for any host in the
2018 the following pattern could be used:
2022 The following pattern
2023 would match any host in the 192.168.0.[0-9] network range:
2025 .Dl Host 192.168.0.?
2029 is a comma-separated list of patterns.
2030 Patterns within pattern-lists may be negated
2031 by preceding them with an exclamation mark
2034 to allow a key to be used from anywhere within an organization
2038 the following entry (in authorized_keys) could be used:
2040 .Dl from=\&"!*.dialup.example.com,*.example.com\&"
2042 Note that a negated match will never produce a positive result by itself.
2043 For example, attempting to match
2045 against the following pattern-list will fail:
2047 .Dl from=\&"!host1,!host2\&"
2049 The solution here is to include a term that will yield a positive match,
2052 .Dl from=\&"!host1,!host2,*\&"
2054 Arguments to some keywords can make use of tokens,
2055 which are expanded at runtime:
2057 .Bl -tag -width XXXX -offset indent -compact
2064 Local user's home directory.
2066 The fingerprint of the server's host key.
2070 hostname or address that is being searched for.
2072 The remote hostname.
2074 A string describing the reason for a
2075 .Cm KnownHostsCommand
2078 when looking up a host by address (only when
2082 when searching by hostname, or
2084 when preparing the host key algorithm preference list to use for the
2089 The base64 encoded host key.
2091 The host key alias if specified, otherwise the original remote hostname given
2092 on the command line.
2096 The local hostname, including the domain name.
2098 The original remote hostname, as given on the command line.
2102 The remote username.
2108 network interface assigned if
2109 tunnel forwarding was requested, or
2113 The type of the server host key, e.g.
2119 .Cm CertificateFile ,
2123 .Cm KnownHostsCommand ,
2129 .Cm UserKnownHostsFile
2130 accept the tokens %%, %C, %d, %h, %i, %k, %L, %l, %n, %p, %r, and %u.
2132 .Cm KnownHostsCommand
2133 additionally accepts the tokens %f, %H, %I, %K and %t.
2136 accepts the tokens %% and %h.
2144 accept the tokens %%, %h, %n, %p, and %r.
2145 .Sh ENVIRONMENT VARIABLES
2146 Arguments to some keywords can be expanded at runtime from environment
2147 variables on the client by enclosing them in
2151 would refer to the user's .ssh directory.
2152 If a specified environment variable does not exist then an error will be
2153 returned and the setting for that keyword will be ignored.
2156 .Cm CertificateFile ,
2160 .Cm KnownHostsCommand ,
2162 .Cm UserKnownHostsFile
2163 support environment variables.
2168 support environment variables only for Unix domain socket paths.
2171 .It Pa ~/.ssh/config
2172 This is the per-user configuration file.
2173 The format of this file is described above.
2174 This file is used by the SSH client.
2175 Because of the potential for abuse, this file must have strict permissions:
2176 read/write for the user, and not writable by others.
2177 .It Pa /etc/ssh/ssh_config
2178 Systemwide configuration file.
2179 This file provides defaults for those
2180 values that are not specified in the user's configuration file, and
2181 for those users who do not have a configuration file.
2182 This file must be world-readable.
2188 OpenSSH is a derivative of the original and free
2189 ssh 1.2.12 release by
2191 .An Aaron Campbell , Bob Beck , Markus Friedl ,
2192 .An Niels Provos , Theo de Raadt
2195 removed many bugs, re-added newer features and
2198 contributed the support for SSH protocol versions 1.5 and 2.0.
projects / FreeBSD / FreeBSD.git / blob