1SSH_CONFIG(5) BSD File Formats Manual SSH_CONFIG(5)
2
4 ssh_config — OpenSSH client configuration file
5
7 ssh(1) obtains configuration data from the following sources in the fol‐
8 lowing order:
9 1. command-line options
11 2. user's configuration file (~/.ssh/config)
12 3. GSSAPI configuration file ($HOME/.ssh/config.gssapi)
13 4. Kerberos configuration file ($HOME/.ssh/config.krb)
14 5. system-wide configuration file (/etc/gsissh/ssh_config)
15 For each parameter, the first obtained value will be used. The configu‐
17 ration files contain sections separated by Host specifications, and that
18 section is only applied for hosts that match one of the patterns given in
19 the specification. The matched host name is usually the one given on the
20 command line (see the CanonicalizeHostname option for exceptions).
21 Since the first obtained value for each parameter is used, more host-spe‐
23 cific declarations should be given near the beginning of the file, and
24 general defaults at the end.
25 The file contains keyword-argument pairs, one per line. Lines starting
27 with ‘#’ and empty lines are interpreted as comments. Arguments may
28 optionally be enclosed in double quotes (") in order to represent argu‐
29 ments containing spaces. Configuration options may be separated by
30 whitespace or optional whitespace and exactly one ‘=’; the latter format
31 is useful to avoid the need to quote whitespace when specifying configu‐
32 ration options using the ssh, scp, and sftp -o option.
33 The possible keywords and their meanings are as follows (note that key‐
35 words are case-insensitive and arguments are case-sensitive):
36 Host Restricts the following declarations (up to the next Host or
38 Match keyword) to be only for those hosts that match one of the
39 patterns given after the keyword. If more than one pattern is
40 provided, they should be separated by whitespace. A single ‘*’
41 as a pattern can be used to provide global defaults for all
42 hosts. The host is usually the hostname argument given on the
43 command line (see the CanonicalizeHostname keyword for excep‐
44 tions).
45 A pattern entry may be negated by prefixing it with an exclama‐
47 tion mark (‘!’). If a negated entry is matched, then the Host
48 entry is ignored, regardless of whether any other patterns on the
49 line match. Negated matches are therefore useful to provide
50 exceptions for wildcard matches.
51 See PATTERNS for more information on patterns.
53 Match Restricts the following declarations (up to the next Host or
55 Match keyword) to be used only when the conditions following the
56 Match keyword are satisfied. Match conditions are specified
57 using one or more criteria or the single token all which always
58 matches. The available criteria keywords are: canonical, final,
59 exec, host, originalhost, user, and localuser. The all criteria
60 must appear alone or immediately after canonical or final. Other
61 criteria may be combined arbitrarily. All criteria but all,
62 canonical, and final require an argument. Criteria may be
63 negated by prepending an exclamation mark (‘!’).
64 The canonical keyword matches only when the configuration file is
66 being re-parsed after hostname canonicalization (see the
67 CanonicalizeHostname option). This may be useful to specify con‐
68 ditions that work with canonical host names only.
69 The final keyword requests that the configuration be re-parsed
71 (regardless of whether CanonicalizeHostname is enabled), and
72 matches only during this final pass. If CanonicalizeHostname is
73 enabled, then canonical and final match during the same pass.
74 The exec keyword executes the specified command under the user's
76 shell. If the command returns a zero exit status then the condi‐
77 tion is considered true. Commands containing whitespace charac‐
78 ters must be quoted. Arguments to exec accept the tokens
79 described in the TOKENS section.
80 The other keywords' criteria must be single entries or comma-sep‐
82 arated lists and may use the wildcard and negation operators
83 described in the PATTERNS section. The criteria for the host
84 keyword are matched against the target hostname, after any sub‐
85 stitution by the Hostname or CanonicalizeHostname options. The
86 originalhost keyword matches against the hostname as it was spec‐
87 ified on the command-line. The user keyword matches against the
88 target username on the remote host. The localuser keyword
89 matches against the name of the local user running ssh(1) (this
90 keyword may be useful in system-wide ssh_config files).
91 AddKeysToAgent
93 Specifies whether keys should be automatically added to a running
94 ssh-agent(1). If this option is set to yes and a key is loaded
95 from a file, the key and its passphrase are added to the agent
96 with the default lifetime, as if by ssh-add(1). If this option
97 is set to ask, ssh(1) will require confirmation using the
98 SSH_ASKPASS program before adding a key (see ssh-add(1) for
99 details). If this option is set to confirm, each use of the key
100 must be confirmed, as if the -c option was specified to
101 ssh-add(1). If this option is set to no, no keys are added to
102 the agent. Alternately, this option may be specified as a time
103 interval using the format described in the TIME FORMATS section
104 of sshd_config(5) to specify the key's lifetime in ssh-agent(1),
105 after which it will automatically be removed. The argument must
106 be no (the default), yes, confirm (optionally followed by a time
107 interval), ask or a time interval.
108 AddressFamily
110 Specifies which address family to use when connecting. Valid
111 arguments are any (the default), inet (use IPv4 only), or inet6
112 (use IPv6 only).
113 BatchMode
115 If set to yes, user interaction such as password prompts and host
116 key confirmation requests will be disabled. This option is use‐
117 ful in scripts and other batch jobs where no user is present to
118 interact with ssh(1). The argument must be yes or no (the
119 default).
120 BindAddress
122 Use the specified address on the local machine as the source
123 address of the connection. Only useful on systems with more than
124 one address.
125 BindInterface
127 Use the address of the specified interface on the local machine
128 as the source address of the connection.
129 CanonicalDomains
131 When CanonicalizeHostname is enabled, this option specifies the
132 list of domain suffixes in which to search for the specified des‐
133 tination host.
134 CanonicalizeFallbackLocal
136 Specifies whether to fail with an error when hostname canonical‐
137 ization fails. The default, yes, will attempt to look up the
138 unqualified hostname using the system resolver's search rules. A
139 value of no will cause ssh(1) to fail instantly if
140 CanonicalizeHostname is enabled and the target hostname cannot be
141 found in any of the domains specified by CanonicalDomains.
142 CanonicalizeHostname
144 Controls whether explicit hostname canonicalization is performed.
145 The default, no, is not to perform any name rewriting and let the
146 system resolver handle all hostname lookups. If set to yes then,
147 for connections that do not use a ProxyCommand or ProxyJump,
148 ssh(1) will attempt to canonicalize the hostname specified on the
149 command line using the CanonicalDomains suffixes and
150 CanonicalizePermittedCNAMEs rules. If CanonicalizeHostname is
151 set to always, then canonicalization is applied to proxied con‐
152 nections too.
153 If this option is enabled, then the configuration files are pro‐
155 cessed again using the new target name to pick up any new config‐
156 uration in matching Host and Match stanzas.
157 CanonicalizeMaxDots
159 Specifies the maximum number of dot characters in a hostname
160 before canonicalization is disabled. The default, 1, allows a
161 single dot (i.e. hostname.subdomain).
162 CanonicalizePermittedCNAMEs
164 Specifies rules to determine whether CNAMEs should be followed
165 when canonicalizing hostnames. The rules consist of one or more
166 arguments of source_domain_list:target_domain_list, where
167 source_domain_list is a pattern-list of domains that may follow
168 CNAMEs in canonicalization, and target_domain_list is a pattern-
169 list of domains that they may resolve to.
170 For example, "*.a.example.com:*.b.example.com,*.c.example.com"
172 will allow hostnames matching "*.a.example.com" to be canonical‐
173 ized to names in the "*.b.example.com" or "*.c.example.com"
174 domains.
175 CASignatureAlgorithms
177 The default is handled system-wide by crypto-policies(7). To see
178 the defaults and how to modify this default, see manual page
179 update-crypto-policies(8).
180 Specifies which algorithms are allowed for signing of certifi‐
182 cates by certificate authorities (CAs). ssh(1) will not accept
183 host certificates signed using algorithms other than those speci‐
184 fied.
185 CertificateFile
187 Specifies a file from which the user's certificate is read. A
188 corresponding private key must be provided separately in order to
189 use this certificate either from an IdentityFile directive or -i
190 flag to ssh(1), via ssh-agent(1), or via a PKCS11Provider or
191 SecurityKeyProvider.
192 Arguments to CertificateFile may use the tilde syntax to refer to
194 a user's home directory, the tokens described in the TOKENS sec‐
195 tion and environment variables as described in the ENVIRONMENT
196 VARIABLES section.
197 It is possible to have multiple certificate files specified in
199 configuration files; these certificates will be tried in
200 sequence. Multiple CertificateFile directives will add to the
201 list of certificates used for authentication.
202 ChallengeResponseAuthentication
204 Specifies whether to use challenge-response authentication. The
205 argument to this keyword must be yes (the default) or no.
206 CheckHostIP
208 If set to yes (the default), ssh(1) will additionally check the
209 host IP address in the known_hosts file. This allows it to
210 detect if a host key changed due to DNS spoofing and will add
211 addresses of destination hosts to ~/.ssh/known_hosts in the
212 process, regardless of the setting of StrictHostKeyChecking. If
213 the option is set to no, the check will not be executed.
214 Ciphers
216 The default is handled system-wide by crypto-policies(7). To see
217 the defaults and how to modify this default, see manual page
218 update-crypto-policies(8).
219 Specifies the ciphers allowed and their order of preference.
221 Multiple ciphers must be comma-separated. If the specified list
222 begins with a ‘+’ character, then the specified ciphers will be
223 appended to the built-in openssh default set instead of replacing
224 them. If the specified list begins with a ‘-’ character, then
225 the specified ciphers (including wildcards) will be removed from
226 the built-in openssh default set instead of replacing them. If
227 the specified list begins with a ‘^’ character, then the speci‐
228 fied ciphers will be placed at the head of the built-in openssh
229 default set.
230 The supported ciphers are:
232 3des-cbc
234 aes128-cbc
235 aes192-cbc
236 aes256-cbc
237 aes128-ctr
238 aes192-ctr
239 aes256-ctr
240 aes128-gcm@openssh.com
241 aes256-gcm@openssh.com
242 chacha20-poly1305@openssh.com
243 The list of available ciphers may also be obtained using "ssh -Q
245 cipher".
246 ClearAllForwardings
248 Specifies that all local, remote, and dynamic port forwardings
249 specified in the configuration files or on the command line be
250 cleared. This option is primarily useful when used from the
251 ssh(1) command line to clear port forwardings set in configura‐
252 tion files, and is automatically set by scp(1) and sftp(1). The
253 argument must be yes or no (the default).
254 Compression
256 Specifies whether to use compression. The argument must be yes
257 or no (the default).
258 ConnectionAttempts
260 Specifies the number of tries (one per second) to make before
261 exiting. The argument must be an integer. This may be useful in
262 scripts if the connection sometimes fails. The default is 1.
263 ConnectTimeout
265 Specifies the timeout (in seconds) used when connecting to the
266 SSH server, instead of using the default system TCP timeout.
267 This timeout is applied both to establishing the connection and
268 to performing the initial SSH protocol handshake and key
269 exchange.
270 ControlMaster
272 Enables the sharing of multiple sessions over a single network
273 connection. When set to yes, ssh(1) will listen for connections
274 on a control socket specified using the ControlPath argument.
275 Additional sessions can connect to this socket using the same
276 ControlPath with ControlMaster set to no (the default). These
277 sessions will try to reuse the master instance's network connec‐
278 tion rather than initiating new ones, but will fall back to con‐
279 necting normally if the control socket does not exist, or is not
280 listening.
281 Setting this to ask will cause ssh(1) to listen for control con‐
283 nections, but require confirmation using ssh-askpass(1). If the
284 ControlPath cannot be opened, ssh(1) will continue without con‐
285 necting to a master instance.
286 X11 and ssh-agent(1) forwarding is supported over these multi‐
288 plexed connections, however the display and agent forwarded will
289 be the one belonging to the master connection i.e. it is not pos‐
290 sible to forward multiple displays or agents.
291 Two additional options allow for opportunistic multiplexing: try
293 to use a master connection but fall back to creating a new one if
294 one does not already exist. These options are: auto and autoask.
295 The latter requires confirmation like the ask option.
296 ControlPath
298 Specify the path to the control socket used for connection shar‐
299 ing as described in the ControlMaster section above or the string
300 none to disable connection sharing. Arguments to ControlPath may
301 use the tilde syntax to refer to a user's home directory, the
302 tokens described in the TOKENS section and environment variables
303 as described in the ENVIRONMENT VARIABLES section. It is recom‐
304 mended that any ControlPath used for opportunistic connection
305 sharing include at least %h, %p, and %r (or alternatively %C) and
306 be placed in a directory that is not writable by other users.
307 This ensures that shared connections are uniquely identified.
308 ControlPersist
310 When used in conjunction with ControlMaster, specifies that the
311 master connection should remain open in the background (waiting
312 for future client connections) after the initial client connec‐
313 tion has been closed. If set to no (the default), then the mas‐
314 ter connection will not be placed into the background, and will
315 close as soon as the initial client connection is closed. If set
316 to yes or 0, then the master connection will remain in the back‐
317 ground indefinitely (until killed or closed via a mechanism such
318 as the "ssh -O exit"). If set to a time in seconds, or a time in
319 any of the formats documented in sshd_config(5), then the back‐
320 grounded master connection will automatically terminate after it
321 has remained idle (with no client connections) for the specified
322 time.
323 DynamicForward
325 Specifies that a TCP port on the local machine be forwarded over
326 the secure channel, and the application protocol is then used to
327 determine where to connect to from the remote machine.
328 The argument must be [bind_address:]port. IPv6 addresses can be
330 specified by enclosing addresses in square brackets. By default,
331 the local port is bound in accordance with the GatewayPorts set‐
332 ting. However, an explicit bind_address may be used to bind the
333 connection to a specific address. The bind_address of localhost
334 indicates that the listening port be bound for local use only,
335 while an empty address or ‘*’ indicates that the port should be
336 available from all interfaces.
337 Currently the SOCKS4 and SOCKS5 protocols are supported, and
339 ssh(1) will act as a SOCKS server. Multiple forwardings may be
340 specified, and additional forwardings can be given on the command
341 line. Only the superuser can forward privileged ports.
342 EnableSSHKeysign
344 Setting this option to yes in the global client configuration
345 file /etc/gsissh/ssh_config enables the use of the helper program
346 ssh-keysign(8) during HostbasedAuthentication. The argument must
347 be yes or no (the default). This option should be placed in the
348 non-hostspecific section. See ssh-keysign(8) for more informa‐
349 tion.
350 EscapeChar
352 Sets the escape character (default: ‘~’). The escape character
353 can also be set on the command line. The argument should be a
354 single character, ‘^’ followed by a letter, or none to disable
355 the escape character entirely (making the connection transparent
356 for binary data).
357 ExitOnForwardFailure
359 Specifies whether ssh(1) should terminate the connection if it
360 cannot set up all requested dynamic, tunnel, local, and remote
361 port forwardings, (e.g. if either end is unable to bind and lis‐
362 ten on a specified port). Note that ExitOnForwardFailure does
363 not apply to connections made over port forwardings and will not,
364 for example, cause ssh(1) to exit if TCP connections to the ulti‐
365 mate forwarding destination fail. The argument must be yes or no
366 (the default).
367 FingerprintHash
369 Specifies the hash algorithm used when displaying key finger‐
370 prints. Valid options are: md5 and sha256 (the default).
371 ForwardAgent
373 Specifies whether the connection to the authentication agent (if
374 any) will be forwarded to the remote machine. The argument may
375 be yes, no (the default), an explicit path to an agent socket or
376 the name of an environment variable (beginning with ‘$’) in which
377 to find the path.
378 Agent forwarding should be enabled with caution. Users with the
380 ability to bypass file permissions on the remote host (for the
381 agent's Unix-domain socket) can access the local agent through
382 the forwarded connection. An attacker cannot obtain key material
383 from the agent, however they can perform operations on the keys
384 that enable them to authenticate using the identities loaded into
385 the agent.
386 ForwardX11
388 Specifies whether X11 connections will be automatically redi‐
389 rected over the secure channel and DISPLAY set. The argument
390 must be yes or no (the default).
391 X11 forwarding should be enabled with caution. Users with the
393 ability to bypass file permissions on the remote host (for the
394 user's X11 authorization database) can access the local X11 dis‐
395 play through the forwarded connection. An attacker may then be
396 able to perform activities such as keystroke monitoring if the
397 ForwardX11Trusted option is also enabled.
398 ForwardX11Timeout
400 Specify a timeout for untrusted X11 forwarding using the format
401 described in the TIME FORMATS section of sshd_config(5). X11
402 connections received by ssh(1) after this time will be refused.
403 Setting ForwardX11Timeout to zero will disable the timeout and
404 permit X11 forwarding for the life of the connection. The
405 default is to disable untrusted X11 forwarding after twenty min‐
406 utes has elapsed.
407 ForwardX11Trusted
409 If this option is set to yes, remote X11 clients will have full
410 access to the original X11 display.
411 If this option is set to no (the default), remote X11 clients
413 will be considered untrusted and prevented from stealing or tam‐
414 pering with data belonging to trusted X11 clients. Furthermore,
415 the xauth(1) token used for the session will be set to expire
416 after 20 minutes. Remote clients will be refused access after
417 this time.
418 See the X11 SECURITY extension specification for full details on
420 the restrictions imposed on untrusted clients.
421 GatewayPorts
423 Specifies whether remote hosts are allowed to connect to local
424 forwarded ports. By default, ssh(1) binds local port forwardings
425 to the loopback address. This prevents other remote hosts from
426 connecting to forwarded ports. GatewayPorts can be used to spec‐
427 ify that ssh should bind local port forwardings to the wildcard
428 address, thus allowing remote hosts to connect to forwarded
429 ports. The argument must be yes or no (the default).
430 GlobalKnownHostsFile
432 Specifies one or more files to use for the global host key data‐
433 base, separated by whitespace. The default is
434 /etc/gsissh/ssh_known_hosts, /etc/gsissh/ssh_known_hosts2.
435 GSSAPIAuthentication
437 Specifies whether user authentication based on GSSAPI is allowed.
438 The default is yes.
439 GSSAPIClientIdentity
441 If set, specifies the GSSAPI client identity that ssh should use
442 when connecting to the server. The default is unset, which means
443 that the default identity will be used.
444 GSSAPIDelegateCredentials
446 Forward (delegate) credentials to the server. The default is
447 yes.
448 GSSAPIKeyExchange
450 Specifies whether key exchange based on GSSAPI may be used. When
451 using GSSAPI key exchange the server need not have a host key.
452 The default is “yes”.
453 GSSAPIRenewalForcesRekey
455 If set to “yes” then renewal of the client's GSSAPI credentials
456 will force the rekeying of the ssh connection. With a compatible
457 server, this will delegate the renewed credentials to a session
458 on the server.
459 Checks are made to ensure that credentials are only propagated
461 when the new credentials match the old ones on the originating
462 client and where the receiving server still has the old set in
463 its cache.
464 The default is “no”.
466 For this to work GSSAPIKeyExchange needs to be enabled in the
468 server and also used by the client.
469 GSSAPIServerIdentity
471 If set, specifies the GSSAPI server identity that ssh should
472 expect when connecting to the server. The default is unset, which
473 means that the expected GSSAPI server identity will be determined
474 from the target hostname.
475 GSSAPITrustDns
477 Set to “yes” to indicate that the DNS is trusted to securely
478 canonicalize the name of the host being connected to. If “no”,
479 the hostname entered on the command line will be passed untouched
480 to the GSSAPI library. The default is “no”.
481 GSSAPIKexAlgorithms
483 The default is handled system-wide by crypto-policies(7). To see
484 the defaults and how to modify this default, see manual page
485 update-crypto-policies(8).
486 The list of key exchange algorithms that are offered for GSSAPI
488 key exchange. Possible values are
489 gss-gex-sha1-,
491 gss-group1-sha1-,
492 gss-group14-sha1-,
493 gss-group14-sha256-,
494 gss-group16-sha512-,
495 gss-nistp256-sha256-,
496 gss-curve25519-sha256-
497 This option only applies to connections using GSSAPI.
499 HashKnownHosts
501 Indicates that ssh(1) should hash host names and addresses when
502 they are added to ~/.ssh/known_hosts. These hashed names may be
503 used normally by ssh(1) and sshd(8), but they do not visually
504 reveal identifying information if the file's contents are dis‐
505 closed. The default is no. Note that existing names and
506 addresses in known hosts files will not be converted automati‐
507 cally, but may be manually hashed using ssh-keygen(1).
508 HostbasedAuthentication
510 Specifies whether to try rhosts based authentication with public
511 key authentication. The argument must be yes or no (the
512 default).
513 HostbasedKeyTypes
515 Specifies the key types that will be used for hostbased authenti‐
516 cation as a comma-separated list of patterns. Alternately if the
517 specified list begins with a ‘+’ character, then the specified
518 key types will be appended to the default set instead of replac‐
519 ing them. If the specified list begins with a ‘-’ character,
520 then the specified key types (including wildcards) will be
521 removed from the default set instead of replacing them. If the
522 specified list begins with a ‘^’ character, then the specified
523 key types will be placed at the head of the default set. The
524 default for this option is:
525 ecdsa-sha2-nistp256-cert-v01@openssh.com,
527 ecdsa-sha2-nistp384-cert-v01@openssh.com,
528 ecdsa-sha2-nistp521-cert-v01@openssh.com,
529 sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
530 ssh-ed25519-cert-v01@openssh.com,
531 sk-ssh-ed25519-cert-v01@openssh.com,
532 rsa-sha2-512-cert-v01@openssh.com,
533 rsa-sha2-256-cert-v01@openssh.com,
534 ssh-rsa-cert-v01@openssh.com,
535 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
536 sk-ecdsa-sha2-nistp256@openssh.com,
537 ssh-ed25519,sk-ssh-ed25519@openssh.com,
538 rsa-sha2-512,rsa-sha2-256,ssh-rsa
539 The -Q option of ssh(1) may be used to list supported key types.
541 HostKeyAlgorithms
543 Specifies the host key algorithms that the client wants to use in
544 order of preference. Alternately if the specified list begins
545 with a ‘+’ character, then the specified key types will be
546 appended to the default set instead of replacing them. If the
547 specified list begins with a ‘-’ character, then the specified
548 key types (including wildcards) will be removed from the default
549 set instead of replacing them. If the specified list begins with
550 a ‘^’ character, then the specified key types will be placed at
551 the head of the default set. The default for this option is:
552 ecdsa-sha2-nistp256-cert-v01@openssh.com,
554 ecdsa-sha2-nistp384-cert-v01@openssh.com,
555 ecdsa-sha2-nistp521-cert-v01@openssh.com,
556 sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
557 ssh-ed25519-cert-v01@openssh.com,
558 sk-ssh-ed25519-cert-v01@openssh.com,
559 rsa-sha2-512-cert-v01@openssh.com,
560 rsa-sha2-256-cert-v01@openssh.com,
561 ssh-rsa-cert-v01@openssh.com,
562 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
563 sk-ecdsa-sha2-nistp256@openssh.com,
564 ssh-ed25519,sk-ssh-ed25519@openssh.com,
565 rsa-sha2-512,rsa-sha2-256,ssh-rsa
566 If hostkeys are known for the destination host then this default
568 is modified to prefer their algorithms.
569 The list of available key types may also be obtained using "ssh
571 -Q HostKeyAlgorithms".
572 HostKeyAlias
574 Specifies an alias that should be used instead of the real host
575 name when looking up or saving the host key in the host key data‐
576 base files and when validating host certificates. This option is
577 useful for tunneling SSH connections or for multiple servers run‐
578 ning on a single host.
579 Hostname
581 Specifies the real host name to log into. This can be used to
582 specify nicknames or abbreviations for hosts. Arguments to
583 Hostname accept the tokens described in the TOKENS section.
584 Numeric IP addresses are also permitted (both on the command line
585 and in Hostname specifications). The default is the name given
586 on the command line.
587 IdentitiesOnly
589 Specifies that ssh(1) should only use the configured authentica‐
590 tion identity and certificate files (either the default files, or
591 those explicitly configured in the ssh_config files or passed on
592 the ssh(1) command-line), even if ssh-agent(1) or a
593 PKCS11Provider or SecurityKeyProvider offers more identities.
594 The argument to this keyword must be yes or no (the default).
595 This option is intended for situations where ssh-agent offers
596 many different identities.
597 IdentityAgent
599 Specifies the UNIX-domain socket used to communicate with the
600 authentication agent.
601 This option overrides the SSH_AUTH_SOCK environment variable and
603 can be used to select a specific agent. Setting the socket name
604 to none disables the use of an authentication agent. If the
605 string "SSH_AUTH_SOCK" is specified, the location of the socket
606 will be read from the SSH_AUTH_SOCK environment variable. Other‐
607 wise if the specified value begins with a ‘$’ character, then it
608 will be treated as an environment variable containing the loca‐
609 tion of the socket.
610 Arguments to IdentityAgent may use the tilde syntax to refer to a
612 user's home directory, the tokens described in the TOKENS section
613 and environment variables as described in the ENVIRONMENT
614 VARIABLES section.
615 IdentityFile
617 Specifies a file from which the user's DSA, ECDSA, authenticator-
618 hosted ECDSA, Ed25519, authenticator-hosted Ed25519 or RSA
619 authentication identity is read. The default is ~/.ssh/id_dsa,
620 ~/.ssh/id_ecdsa, ~/.ssh/id_ecdsa_sk, ~/.ssh/id_ed25519,
621 ~/.ssh/id_ed25519_sk and ~/.ssh/id_rsa. Additionally, any iden‐
622 tities represented by the authentication agent will be used for
623 authentication unless IdentitiesOnly is set. If no certificates
624 have been explicitly specified by CertificateFile, ssh(1) will
625 try to load certificate information from the filename obtained by
626 appending -cert.pub to the path of a specified IdentityFile.
627 Arguments to IdentityFile may use the tilde syntax to refer to a
629 user's home directory or the tokens described in the TOKENS sec‐
630 tion.
631 It is possible to have multiple identity files specified in con‐
633 figuration files; all these identities will be tried in sequence.
634 Multiple IdentityFile directives will add to the list of identi‐
635 ties tried (this behaviour differs from that of other configura‐
636 tion directives).
637 IdentityFile may be used in conjunction with IdentitiesOnly to
639 select which identities in an agent are offered during authenti‐
640 cation. IdentityFile may also be used in conjunction with
641 CertificateFile in order to provide any certificate also needed
642 for authentication with the identity.
643 The authentication identity can be also specified in a form of
645 PKCS#11 URI starting with a string pkcs11:. There is supported a
646 subset of the PKCS#11 URI as defined in RFC 7512 (implemented
647 path arguments id, manufacturer, object, token and query argu‐
648 ments module-path and pin-value ). The URI can not be in quotes.
649 IgnoreUnknown
651 Specifies a pattern-list of unknown options to be ignored if they
652 are encountered in configuration parsing. This may be used to
653 suppress errors if ssh_config contains options that are unrecog‐
654 nised by ssh(1). It is recommended that IgnoreUnknown be listed
655 early in the configuration file as it will not be applied to
656 unknown options that appear before it.
657 Include
659 Include the specified configuration file(s). Multiple pathnames
660 may be specified and each pathname may contain glob(7) wildcards
661 and, for user configurations, shell-like ‘~’ references to user
662 home directories. Wildcards will be expanded and processed in
663 lexical order. Files without absolute paths are assumed to be in
664 ~/.ssh if included in a user configuration file or /etc/ssh if
665 included from the system configuration file. Include directive
666 may appear inside a Match or Host block to perform conditional
667 inclusion.
668 IPQoS Specifies the IPv4 type-of-service or DSCP class for connections.
670 Accepted values are af11, af12, af13, af21, af22, af23, af31,
671 af32, af33, af41, af42, af43, cs0, cs1, cs2, cs3, cs4, cs5, cs6,
672 cs7, ef, le, lowdelay, throughput, reliability, a numeric value,
673 or none to use the operating system default. This option may
674 take one or two arguments, separated by whitespace. If one argu‐
675 ment is specified, it is used as the packet class uncondition‐
676 ally. If two values are specified, the first is automatically
677 selected for interactive sessions and the second for non-interac‐
678 tive sessions. The default is af21 (Low-Latency Data) for inter‐
679 active sessions and cs1 (Lower Effort) for non-interactive ses‐
680 sions.
681 KbdInteractiveAuthentication
683 Specifies whether to use keyboard-interactive authentication.
684 The argument to this keyword must be yes (the default) or no.
685 KbdInteractiveDevices
687 Specifies the list of methods to use in keyboard-interactive
688 authentication. Multiple method names must be comma-separated.
689 The default is to use the server specified list. The methods
690 available vary depending on what the server supports. For an
691 OpenSSH server, it may be zero or more of: bsdauth and pam.
692 KexAlgorithms
694 The default is handled system-wide by crypto-policies(7). To see
695 the defaults and how to modify this default, see manual page
696 update-crypto-policies(8).
697 Specifies the available KEX (Key Exchange) algorithms. Multiple
699 algorithms must be comma-separated. If the specified list begins
700 with a ‘+’ character, then the specified methods will be appended
701 to the built-in openssh default set instead of replacing them.
702 If the specified list begins with a ‘-’ character, then the spec‐
703 ified methods (including wildcards) will be removed from the
704 built-in openssh default set instead of replacing them. If the
705 specified list begins with a ‘^’ character, then the specified
706 methods will be placed at the head of the built-in openssh
707 default set.
708 The list of available key exchange algorithms may also be
710 obtained using "ssh -Q kex".
711 LocalCommand
713 Specifies a command to execute on the local machine after suc‐
714 cessfully connecting to the server. The command string extends
715 to the end of the line, and is executed with the user's shell.
716 Arguments to LocalCommand accept the tokens described in the
717 TOKENS section.
718 The command is run synchronously and does not have access to the
720 session of the ssh(1) that spawned it. It should not be used for
721 interactive commands.
722 This directive is ignored unless PermitLocalCommand has been
724 enabled.
725 LocalForward
727 Specifies that a TCP port on the local machine be forwarded over
728 the secure channel to the specified host and port from the remote
729 machine. The first argument specifies the listener and may be
730 [bind_address:]port or a Unix domain socket path. The second
731 argument is the destination and may be host:hostport or a Unix
732 domain socket path if the remote host supports it.
733 IPv6 addresses can be specified by enclosing addresses in square
735 brackets. Multiple forwardings may be specified, and additional
736 forwardings can be given on the command line. Only the superuser
737 can forward privileged ports. By default, the local port is
738 bound in accordance with the GatewayPorts setting. However, an
739 explicit bind_address may be used to bind the connection to a
740 specific address. The bind_address of localhost indicates that
741 the listening port be bound for local use only, while an empty
742 address or ‘*’ indicates that the port should be available from
743 all interfaces. Unix domain socket paths may use the tokens
744 described in the TOKENS section and environment variables as
745 described in the ENVIRONMENT VARIABLES section.
746 LogLevel
748 Gives the verbosity level that is used when logging messages from
749 ssh(1). The possible values are: QUIET, FATAL, ERROR, INFO, VER‐
750 BOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO.
751 DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify
752 higher levels of verbose output.
753 MACs The default is handled system-wide by crypto-policies(7). To see
755 the defaults and how to modify this default, see manual page
756 update-crypto-policies(8).
757 Specifies the MAC (message authentication code) algorithms in
759 order of preference. The MAC algorithm is used for data
760 integrity protection. Multiple algorithms must be comma-sepa‐
761 rated. If the specified list begins with a ‘+’ character, then
762 the specified algorithms will be appended to the built-in openssh
763 default set instead of replacing them. If the specified list
764 begins with a ‘-’ character, then the specified algorithms
765 (including wildcards) will be removed from the built-in openssh
766 default set instead of replacing them. If the specified list
767 begins with a ‘^’ character, then the specified algorithms will
768 be placed at the head of the built-in openssh default set.
769 The algorithms that contain "-etm" calculate the MAC after
771 encryption (encrypt-then-mac). These are considered safer and
772 their use recommended.
773 The list of available MAC algorithms may also be obtained using
775 "ssh -Q mac".
776 NoHostAuthenticationForLocalhost
778 Disable host authentication for localhost (loopback addresses).
779 The argument to this keyword must be yes or no (the default).
780 NumberOfPasswordPrompts
782 Specifies the number of password prompts before giving up. The
783 argument to this keyword must be an integer. The default is 3.
784 PasswordAuthentication
786 Specifies whether to use password authentication. The argument
787 to this keyword must be yes (the default) or no.
788 PermitLocalCommand
790 Allow local command execution via the LocalCommand option or
791 using the !command escape sequence in ssh(1). The argument must
792 be yes or no (the default).
793 PKCS11Provider
795 Specifies which PKCS#11 provider to use or none to indicate that
796 no provider should be used (the default). The argument to this
797 keyword is a path to the PKCS#11 shared library ssh(1) should use
798 to communicate with a PKCS#11 token providing keys for user
799 authentication.
800 Port Specifies the port number to connect on the remote host. The
802 default is 22.
803 PreferredAuthentications
805 Specifies the order in which the client should try authentication
806 methods. This allows a client to prefer one method (e.g.
807 keyboard-interactive) over another method (e.g. password). The
808 default is:
809 gssapi-keyex,gssapi-with-mic,hostbased,publickey,
811 keyboard-interactive,password
812 ProxyCommand
814 Specifies the command to use to connect to the server. The com‐
815 mand string extends to the end of the line, and is executed using
816 the user's shell ‘exec’ directive to avoid a lingering shell
817 process.
818 Arguments to ProxyCommand accept the tokens described in the
820 TOKENS section. The command can be basically anything, and
821 should read from its standard input and write to its standard
822 output. It should eventually connect an sshd(8) server running
823 on some machine, or execute sshd -i somewhere. Host key manage‐
824 ment will be done using the Hostname of the host being connected
825 (defaulting to the name typed by the user). Setting the command
826 to none disables this option entirely. Note that CheckHostIP is
827 not available for connects with a proxy command.
828 This directive is useful in conjunction with nc(1) and its proxy
830 support. For example, the following directive would connect via
831 an HTTP proxy at 192.0.2.0:
832 ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
834 ProxyJump
836 Specifies one or more jump proxies as either [user@]host[:port]
837 or an ssh URI. Multiple proxies may be separated by comma char‐
838 acters and will be visited sequentially. Setting this option
839 will cause ssh(1) to connect to the target host by first making a
840 ssh(1) connection to the specified ProxyJump host and then estab‐
841 lishing a TCP forwarding to the ultimate target from there.
842 Note that this option will compete with the ProxyCommand option -
844 whichever is specified first will prevent later instances of the
845 other from taking effect.
846 Note also that the configuration for the destination host (either
848 supplied via the command-line or the configuration file) is not
849 generally applied to jump hosts. ~/.ssh/config should be used if
850 specific configuration is required for jump hosts.
851 ProxyUseFdpass
853 Specifies that ProxyCommand will pass a connected file descriptor
854 back to ssh(1) instead of continuing to execute and pass data.
855 The default is no.
856 PubkeyAcceptedKeyTypes
858 The default is handled system-wide by crypto-policies(7). To see
859 the defaults and how to modify this default, see manual page
860 update-crypto-policies(8).
861 Specifies the key types that will be used for public key authen‐
863 tication as a comma-separated list of patterns. If the specified
864 list begins with a ‘+’ character, then the key types after it
865 will be appended to the built-in openssh default instead of
866 replacing it. If the specified list begins with a ‘-’ character,
867 then the specified key types (including wildcards) will be
868 removed from the built-in openssh default set instead of replac‐
869 ing them. If the specified list begins with a ‘^’ character,
870 then the specified key types will be placed at the head of the
871 built-in openssh default set.
872 The list of available key types may also be obtained using "ssh
874 -Q PubkeyAcceptedKeyTypes".
875 PubkeyAuthentication
877 Specifies whether to try public key authentication. The argument
878 to this keyword must be yes (the default) or no.
879 RekeyLimit
881 Specifies the maximum amount of data that may be transmitted
882 before the session key is renegotiated, optionally followed a
883 maximum amount of time that may pass before the session key is
884 renegotiated. The first argument is specified in bytes and may
885 have a suffix of ‘K’, ‘M’, or ‘G’ to indicate Kilobytes,
886 Megabytes, or Gigabytes, respectively. The default is between
887 ‘1G’ and ‘4G’, depending on the cipher. The optional second
888 value is specified in seconds and may use any of the units docu‐
889 mented in the TIME FORMATS section of sshd_config(5). The
890 default value for RekeyLimit is default none, which means that
891 rekeying is performed after the cipher's default amount of data
892 has been sent or received and no time based rekeying is done.
893 RemoteCommand
895 Specifies a command to execute on the remote machine after suc‐
896 cessfully connecting to the server. The command string extends
897 to the end of the line, and is executed with the user's shell.
898 Arguments to RemoteCommand accept the tokens described in the
899 TOKENS section.
900 RemoteForward
902 Specifies that a TCP port on the remote machine be forwarded over
903 the secure channel. The remote port may either be forwarded to a
904 specified host and port from the local machine, or may act as a
905 SOCKS 4/5 proxy that allows a remote client to connect to arbi‐
906 trary destinations from the local machine. The first argument is
907 the listening specification and may be [bind_address:]port or, if
908 the remote host supports it, a Unix domain socket path. If for‐
909 warding to a specific destination then the second argument must
910 be host:hostport or a Unix domain socket path, otherwise if no
911 destination argument is specified then the remote forwarding will
912 be established as a SOCKS proxy.
913 IPv6 addresses can be specified by enclosing addresses in square
915 brackets. Multiple forwardings may be specified, and additional
916 forwardings can be given on the command line. Privileged ports
917 can be forwarded only when logging in as root on the remote
918 machine. Unix domain socket paths may use the tokens described
919 in the TOKENS section and environment variables as described in
920 the ENVIRONMENT VARIABLES section.
921 If the port argument is 0, the listen port will be dynamically
923 allocated on the server and reported to the client at run time.
924 If the bind_address is not specified, the default is to only bind
926 to loopback addresses. If the bind_address is ‘*’ or an empty
927 string, then the forwarding is requested to listen on all inter‐
928 faces. Specifying a remote bind_address will only succeed if the
929 server's GatewayPorts option is enabled (see sshd_config(5)).
930 RequestTTY
932 Specifies whether to request a pseudo-tty for the session. The
933 argument may be one of: no (never request a TTY), yes (always
934 request a TTY when standard input is a TTY), force (always
935 request a TTY) or auto (request a TTY when opening a login ses‐
936 sion). This option mirrors the -t and -T flags for ssh(1).
937 RevokedHostKeys
939 Specifies revoked host public keys. Keys listed in this file
940 will be refused for host authentication. Note that if this file
941 does not exist or is not readable, then host authentication will
942 be refused for all hosts. Keys may be specified as a text file,
943 listing one public key per line, or as an OpenSSH Key Revocation
944 List (KRL) as generated by ssh-keygen(1). For more information
945 on KRLs, see the KEY REVOCATION LISTS section in ssh-keygen(1).
946 SecurityKeyProvider
948 Specifies a path to a library that will be used when loading any
949 FIDO authenticator-hosted keys, overriding the default of using
950 the built-in USB HID support.
951 If the specified value begins with a ‘$’ character, then it will
953 be treated as an environment variable containing the path to the
954 library.
955 SendEnv
957 Specifies what variables from the local environ(7) should be sent
958 to the server. The server must also support it, and the server
959 must be configured to accept these environment variables. Note
960 that the TERM environment variable is always sent whenever a
961 pseudo-terminal is requested as it is required by the protocol.
962 Refer to AcceptEnv in sshd_config(5) for how to configure the
963 server. Variables are specified by name, which may contain wild‐
964 card characters. Multiple environment variables may be separated
965 by whitespace or spread across multiple SendEnv directives.
966 See PATTERNS for more information on patterns.
968 It is possible to clear previously set SendEnv variable names by
970 prefixing patterns with -. The default is not to send any envi‐
971 ronment variables.
972 ServerAliveCountMax
974 Sets the number of server alive messages (see below) which may be
975 sent without ssh(1) receiving any messages back from the server.
976 If this threshold is reached while server alive messages are
977 being sent, ssh will disconnect from the server, terminating the
978 session. It is important to note that the use of server alive
979 messages is very different from TCPKeepAlive (below). The server
980 alive messages are sent through the encrypted channel and there‐
981 fore will not be spoofable. The TCP keepalive option enabled by
982 TCPKeepAlive is spoofable. The server alive mechanism is valu‐
983 able when the client or server depend on knowing when a connec‐
984 tion has become unresponsive.
985 The default value is 3. If, for example, ServerAliveInterval
987 (see below) is set to 15 and ServerAliveCountMax is left at the
988 default, if the server becomes unresponsive, ssh will disconnect
989 after approximately 45 seconds.
990 ServerAliveInterval
992 Sets a timeout interval in seconds after which if no data has
993 been received from the server, ssh(1) will send a message through
994 the encrypted channel to request a response from the server. The
995 default is 0, indicating that these messages will not be sent to
996 the server.
997 SetEnv Directly specify one or more environment variables and their con‐
999 tents to be sent to the server. Similarly to SendEnv, the server
1000 must be prepared to accept the environment variable.
1001 StreamLocalBindMask
1003 Sets the octal file creation mode mask (umask) used when creating
1004 a Unix-domain socket file for local or remote port forwarding.
1005 This option is only used for port forwarding to a Unix-domain
1006 socket file.
1007 The default value is 0177, which creates a Unix-domain socket
1009 file that is readable and writable only by the owner. Note that
1010 not all operating systems honor the file mode on Unix-domain
1011 socket files.
1012 StreamLocalBindUnlink
1014 Specifies whether to remove an existing Unix-domain socket file
1015 for local or remote port forwarding before creating a new one.
1016 If the socket file already exists and StreamLocalBindUnlink is
1017 not enabled, ssh will be unable to forward the port to the Unix-
1018 domain socket file. This option is only used for port forwarding
1019 to a Unix-domain socket file.
1020 The argument must be yes or no (the default).
1022 StrictHostKeyChecking
1024 If this flag is set to yes, ssh(1) will never automatically add
1025 host keys to the ~/.ssh/known_hosts file, and refuses to connect
1026 to hosts whose host key has changed. This provides maximum pro‐
1027 tection against man-in-the-middle (MITM) attacks, though it can
1028 be annoying when the /etc/gsissh/ssh_known_hosts file is poorly
1029 maintained or when connections to new hosts are frequently made.
1030 This option forces the user to manually add all new hosts.
1031 If this flag is set to “accept-new” then ssh will automatically
1033 add new host keys to the user known hosts files, but will not
1034 permit connections to hosts with changed host keys. If this flag
1035 is set to “no” or “off”, ssh will automatically add new host keys
1036 to the user known hosts files and allow connections to hosts with
1037 changed hostkeys to proceed, subject to some restrictions. If
1038 this flag is set to ask (the default), new host keys will be
1039 added to the user known host files only after the user has con‐
1040 firmed that is what they really want to do, and ssh will refuse
1041 to connect to hosts whose host key has changed. The host keys of
1042 known hosts will be verified automatically in all cases.
1043 SyslogFacility
1045 Gives the facility code that is used when logging messages from
1046 ssh(1). The possible values are: DAEMON, USER, AUTH, LOCAL0,
1047 LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The
1048 default is USER.
1049 TCPKeepAlive
1051 Specifies whether the system should send TCP keepalive messages
1052 to the other side. If they are sent, death of the connection or
1053 crash of one of the machines will be properly noticed. However,
1054 this means that connections will die if the route is down tempo‐
1055 rarily, and some people find it annoying.
1056 The default is yes (to send TCP keepalive messages), and the
1058 client will notice if the network goes down or the remote host
1059 dies. This is important in scripts, and many users want it too.
1060 To disable TCP keepalive messages, the value should be set to no.
1062 See also ServerAliveInterval for protocol-level keepalives.
1063 Tunnel Request tun(4) device forwarding between the client and the
1065 server. The argument must be yes, point-to-point (layer 3),
1066 ethernet (layer 2), or no (the default). Specifying yes requests
1067 the default tunnel mode, which is point-to-point.
1068 TunnelDevice
1070 Specifies the tun(4) devices to open on the client (local_tun)
1071 and the server (remote_tun).
1072 The argument must be local_tun[:remote_tun]. The devices may be
1074 specified by numerical ID or the keyword any, which uses the next
1075 available tunnel device. If remote_tun is not specified, it
1076 defaults to any. The default is any:any.
1077 UpdateHostKeys
1079 Specifies whether ssh(1) should accept notifications of addi‐
1080 tional hostkeys from the server sent after authentication has
1081 completed and add them to UserKnownHostsFile. The argument must
1082 be yes, no or ask. This option allows learning alternate
1083 hostkeys for a server and supports graceful key rotation by
1084 allowing a server to send replacement public keys before old ones
1085 are removed. Additional hostkeys are only accepted if the key
1086 used to authenticate the host was already trusted or explicitly
1087 accepted by the user.
1088 UpdateHostKeys is enabled by default if the user has not overrid‐
1090 den the default UserKnownHostsFile setting, otherwise
1091 UpdateHostKeys will be set to ask.
1092 If UpdateHostKeys is set to ask, then the user is asked to con‐
1094 firm the modifications to the known_hosts file. Confirmation is
1095 currently incompatible with ControlPersist, and will be disabled
1096 if it is enabled.
1097 Presently, only sshd(8) from OpenSSH 6.8 and greater support the
1099 "hostkeys@openssh.com" protocol extension used to inform the
1100 client of all the server's hostkeys.
1101 User Specifies the user to log in as. This can be useful when a dif‐
1103 ferent user name is used on different machines. This saves the
1104 trouble of having to remember to give the user name on the com‐
1105 mand line.
1106 UserKnownHostsFile
1108 Specifies one or more files to use for the user host key data‐
1109 base, separated by whitespace. Each filename may use tilde nota‐
1110 tion to refer to the user's home directory, the tokens described
1111 in the TOKENS section and environment variables as described in
1112 the ENVIRONMENT VARIABLES section. The default is
1113 ~/.ssh/known_hosts, ~/.ssh/known_hosts2.
1114 VerifyHostKeyDNS
1116 Specifies whether to verify the remote key using DNS and SSHFP
1117 resource records. If this option is set to yes, the client will
1118 implicitly trust keys that match a secure fingerprint from DNS.
1119 Insecure fingerprints will be handled as if this option was set
1120 to ask. If this option is set to ask, information on fingerprint
1121 match will be displayed, but the user will still need to confirm
1122 new host keys according to the StrictHostKeyChecking option. The
1123 default is no.
1124 See also VERIFYING HOST KEYS in ssh(1).
1126 VisualHostKey
1128 If this flag is set to yes, an ASCII art representation of the
1129 remote host key fingerprint is printed in addition to the finger‐
1130 print string at login and for unknown host keys. If this flag is
1131 set to no (the default), no fingerprint strings are printed at
1132 login and only the fingerprint string will be printed for unknown
1133 host keys.
1134 XAuthLocation
1136 Specifies the full pathname of the xauth(1) program. The default
1137 is /usr/bin/xauth.
1138
1140 A pattern consists of zero or more non-whitespace characters, ‘*’ (a
1141 wildcard that matches zero or more characters), or ‘?’ (a wildcard that
1142 matches exactly one character). For example, to specify a set of decla‐
1143 rations for any host in the ".co.uk" set of domains, the following pat‐
1144 tern could be used:
1145 Host *.co.uk
1147 The following pattern would match any host in the 192.168.0.[0-9] network
1149 range:
1150 Host 192.168.0.?
1152 A pattern-list is a comma-separated list of patterns. Patterns within
1154 pattern-lists may be negated by preceding them with an exclamation mark
1155 (‘!’). For example, to allow a key to be used from anywhere within an
1156 organization except from the "dialup" pool, the following entry (in
1157 authorized_keys) could be used:
1158 from="!*.dialup.example.com,*.example.com"
1160 Note that a negated match will never produce a positive result by itself.
1162 For example, attempting to match "host3" against the following pattern-
1163 list will fail:
1164 from="!host1,!host2"
1166 The solution here is to include a term that will yield a positive match,
1168 such as a wildcard:
1169 from="!host1,!host2,*"
1171
1173 Arguments to some keywords can make use of tokens, which are expanded at
1174 runtime:
1175 %% A literal ‘%’.
1177 %C Hash of %l%h%p%r.
1178 %d Local user's home directory.
1179 %h The remote hostname.
1180 %i The local user ID.
1181 %k The host key alias if specified, otherwise the orignal remote
1182 hostname given on the command line.
1183 %L The local hostname.
1184 %l The local hostname, including the domain name.
1185 %n The original remote hostname, as given on the command line.
1186 %p The remote port.
1187 %r The remote username.
1188 %T The local tun(4) or tap(4) network interface assigned if tun‐
1189 nel forwarding was requested, or "NONE" otherwise.
1190 %u The local username.
1191 CertificateFile, ControlPath, IdentityAgent, IdentityFile, LocalForward,
1193 Match exec, RemoteCommand, RemoteForward, and UserKnownHostsFile accept
1194 the tokens %%, %C, %d, %h, %i, %L, %l, %n, %p, %r, and %u.
1195 Hostname accepts the tokens %% and %h.
1197 LocalCommand accepts all tokens.
1199 ProxyCommand accepts the tokens %%, %h, %n, %p, and %r.
1201
1203 Arguments to some keywords can be expanded at runtime from environment
1204 variables on the client by enclosing them in ${}, for example
1205 ${HOME}/.ssh would refer to the user's .ssh directory. If a specified
1206 environment variable does not exist then an error will be returned and
1207 the setting for that keyword will be ignored.
1208 The keywords CertificateFile, ControlPath, IdentityAgent, IdentityFile
1210 and UserKnownHostsFile support environment variables. The keywords
1211 LocalForward and RemoteForward support environment variables only for
1212 Unix domain socket paths.
1213
1215 ~/.ssh/config
1216 This is the per-user configuration file. The format of this file
1217 is described above. This file is used by the SSH client.
1218 Because of the potential for abuse, this file must have strict
1219 permissions: read/write for the user, and not writable by others.
1220 /etc/gsissh/ssh_config
1222 Systemwide configuration file. This file provides defaults for
1223 those values that are not specified in the user's configuration
1224 file, and for those users who do not have a configuration file.
1225 This file must be world-readable.
1226
1228 ssh(1)
1229
1231 OpenSSH is a derivative of the original and free ssh 1.2.12 release by
1232 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
1233 de Raadt and Dug Song removed many bugs, re-added newer features and cre‐
1234 ated OpenSSH. Markus Friedl contributed the support for SSH protocol
1235 versions 1.5 and 2.0.
1236BSD August 11, 2020 BSD