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. system-wide configuration file (/etc/ssh/ssh_config)
13 For each parameter, the first obtained value will be used. The configu‐
15 ration files contain sections separated by Host specifications, and that
16 section is only applied for hosts that match one of the patterns given in
17 the specification. The matched host name is usually the one given on the
18 command line (see the CanonicalizeHostname option for exceptions).
19 Since the first obtained value for each parameter is used, more host-spe‐
21 cific declarations should be given near the beginning of the file, and
22 general defaults at the end.
23 The file contains keyword-argument pairs, one per line. Lines starting
25 with ‘#’ and empty lines are interpreted as comments. Arguments may
26 optionally be enclosed in double quotes (") in order to represent argu‐
27 ments containing spaces. Configuration options may be separated by
28 whitespace or optional whitespace and exactly one ‘=’; the latter format
29 is useful to avoid the need to quote whitespace when specifying configu‐
30 ration options using the ssh, scp, and sftp -o option.
31 The possible keywords and their meanings are as follows (note that key‐
33 words are case-insensitive and arguments are case-sensitive):
34 Host Restricts the following declarations (up to the next Host or
36 Match keyword) to be only for those hosts that match one of the
37 patterns given after the keyword. If more than one pattern is
38 provided, they should be separated by whitespace. A single ‘*’
39 as a pattern can be used to provide global defaults for all
40 hosts. The host is usually the hostname argument given on the
41 command line (see the CanonicalizeHostname keyword for excep‐
42 tions).
43 A pattern entry may be negated by prefixing it with an exclama‐
45 tion mark (‘!’). If a negated entry is matched, then the Host
46 entry is ignored, regardless of whether any other patterns on the
47 line match. Negated matches are therefore useful to provide
48 exceptions for wildcard matches.
49 See PATTERNS for more information on patterns.
51 Match Restricts the following declarations (up to the next Host or
53 Match keyword) to be used only when the conditions following the
54 Match keyword are satisfied. Match conditions are specified
55 using one or more criteria or the single token all which always
56 matches. The available criteria keywords are: canonical, final,
57 exec, host, originalhost, user, and localuser. The all criteria
58 must appear alone or immediately after canonical or final. Other
59 criteria may be combined arbitrarily. All criteria but all,
60 canonical, and final require an argument. Criteria may be
61 negated by prepending an exclamation mark (‘!’).
62 The canonical keyword matches only when the configuration file is
64 being re-parsed after hostname canonicalization (see the
65 CanonicalizeHostname option). This may be useful to specify con‐
66 ditions that work with canonical host names only.
67 The final keyword requests that the configuration be re-parsed
69 (regardless of whether CanonicalizeHostname is enabled), and
70 matches only during this final pass. If CanonicalizeHostname is
71 enabled, then canonical and final match during the same pass.
72 The exec keyword executes the specified command under the user's
74 shell. If the command returns a zero exit status then the condi‐
75 tion is considered true. Commands containing whitespace charac‐
76 ters must be quoted. Arguments to exec accept the tokens
77 described in the TOKENS section.
78 The other keywords' criteria must be single entries or comma-sep‐
80 arated lists and may use the wildcard and negation operators
81 described in the PATTERNS section. The criteria for the host
82 keyword are matched against the target hostname, after any sub‐
83 stitution by the Hostname or CanonicalizeHostname options. The
84 originalhost keyword matches against the hostname as it was spec‐
85 ified on the command-line. The user keyword matches against the
86 target username on the remote host. The localuser keyword
87 matches against the name of the local user running ssh(1) (this
88 keyword may be useful in system-wide ssh_config files).
89 AddKeysToAgent
91 Specifies whether keys should be automatically added to a running
92 ssh-agent(1). If this option is set to yes and a key is loaded
93 from a file, the key and its passphrase are added to the agent
94 with the default lifetime, as if by ssh-add(1). If this option
95 is set to ask, ssh(1) will require confirmation using the
96 SSH_ASKPASS program before adding a key (see ssh-add(1) for
97 details). If this option is set to confirm, each use of the key
98 must be confirmed, as if the -c option was specified to
99 ssh-add(1). If this option is set to no, no keys are added to
100 the agent. Alternately, this option may be specified as a time
101 interval using the format described in the TIME FORMATS section
102 of sshd_config(5) to specify the key's lifetime in ssh-agent(1),
103 after which it will automatically be removed. The argument must
104 be no (the default), yes, confirm (optionally followed by a time
105 interval), ask or a time interval.
106 AddressFamily
108 Specifies which address family to use when connecting. Valid
109 arguments are any (the default), inet (use IPv4 only), or inet6
110 (use IPv6 only).
111 BatchMode
113 If set to yes, user interaction such as password prompts and host
114 key confirmation requests will be disabled. This option is use‐
115 ful in scripts and other batch jobs where no user is present to
116 interact with ssh(1). The argument must be yes or no (the
117 default).
118 BindAddress
120 Use the specified address on the local machine as the source
121 address of the connection. Only useful on systems with more than
122 one address.
123 BindInterface
125 Use the address of the specified interface on the local machine
126 as the source address of the connection.
127 CanonicalDomains
129 When CanonicalizeHostname is enabled, this option specifies the
130 list of domain suffixes in which to search for the specified des‐
131 tination host.
132 CanonicalizeFallbackLocal
134 Specifies whether to fail with an error when hostname canonical‐
135 ization fails. The default, yes, will attempt to look up the
136 unqualified hostname using the system resolver's search rules. A
137 value of no will cause ssh(1) to fail instantly if
138 CanonicalizeHostname is enabled and the target hostname cannot be
139 found in any of the domains specified by CanonicalDomains.
140 CanonicalizeHostname
142 Controls whether explicit hostname canonicalization is performed.
143 The default, no, is not to perform any name rewriting and let the
144 system resolver handle all hostname lookups. If set to yes then,
145 for connections that do not use a ProxyCommand or ProxyJump,
146 ssh(1) will attempt to canonicalize the hostname specified on the
147 command line using the CanonicalDomains suffixes and
148 CanonicalizePermittedCNAMEs rules. If CanonicalizeHostname is
149 set to always, then canonicalization is applied to proxied con‐
150 nections too.
151 If this option is enabled, then the configuration files are pro‐
153 cessed again using the new target name to pick up any new config‐
154 uration in matching Host and Match stanzas.
155 CanonicalizeMaxDots
157 Specifies the maximum number of dot characters in a hostname
158 before canonicalization is disabled. The default, 1, allows a
159 single dot (i.e. hostname.subdomain).
160 CanonicalizePermittedCNAMEs
162 Specifies rules to determine whether CNAMEs should be followed
163 when canonicalizing hostnames. The rules consist of one or more
164 arguments of source_domain_list:target_domain_list, where
165 source_domain_list is a pattern-list of domains that may follow
166 CNAMEs in canonicalization, and target_domain_list is a pattern-
167 list of domains that they may resolve to.
168 For example, "*.a.example.com:*.b.example.com,*.c.example.com"
170 will allow hostnames matching "*.a.example.com" to be canonical‐
171 ized to names in the "*.b.example.com" or "*.c.example.com"
172 domains.
173 CASignatureAlgorithms
175 The default is handled system-wide by crypto-policies(7). To see
176 the defaults and how to modify this default, see manual page
177 update-crypto-policies(8).
178 Specifies which algorithms are allowed for signing of certifi‐
180 cates by certificate authorities (CAs). ssh(1) will not accept
181 host certificates signed using algorithms other than those speci‐
182 fied.
183 CertificateFile
185 Specifies a file from which the user's certificate is read. A
186 corresponding private key must be provided separately in order to
187 use this certificate either from an IdentityFile directive or -i
188 flag to ssh(1), via ssh-agent(1), or via a PKCS11Provider or
189 SecurityKeyProvider.
190 Arguments to CertificateFile may use the tilde syntax to refer to
192 a user's home directory, the tokens described in the TOKENS sec‐
193 tion and environment variables as described in the ENVIRONMENT
194 VARIABLES section.
195 It is possible to have multiple certificate files specified in
197 configuration files; these certificates will be tried in
198 sequence. Multiple CertificateFile directives will add to the
199 list of certificates used for authentication.
200 ChallengeResponseAuthentication
202 Specifies whether to use challenge-response authentication. The
203 argument to this keyword must be yes (the default) or no.
204 CheckHostIP
206 If set to yes (the default), ssh(1) will additionally check the
207 host IP address in the known_hosts file. This allows it to
208 detect if a host key changed due to DNS spoofing and will add
209 addresses of destination hosts to ~/.ssh/known_hosts in the
210 process, regardless of the setting of StrictHostKeyChecking. If
211 the option is set to no, the check will not be executed.
212 Ciphers
214 The default is handled system-wide by crypto-policies(7). To see
215 the defaults and how to modify this default, see manual page
216 update-crypto-policies(8).
217 Specifies the ciphers allowed and their order of preference.
219 Multiple ciphers must be comma-separated. If the specified list
220 begins with a ‘+’ character, then the specified ciphers will be
221 appended to the built-in openssh default set instead of replacing
222 them. If the specified list begins with a ‘-’ character, then
223 the specified ciphers (including wildcards) will be removed from
224 the built-in openssh default set instead of replacing them. If
225 the specified list begins with a ‘^’ character, then the speci‐
226 fied ciphers will be placed at the head of the built-in openssh
227 default set.
228 The supported ciphers are:
230 3des-cbc
232 aes128-cbc
233 aes192-cbc
234 aes256-cbc
235 aes128-ctr
236 aes192-ctr
237 aes256-ctr
238 aes128-gcm@openssh.com
239 aes256-gcm@openssh.com
240 chacha20-poly1305@openssh.com
241 The list of available ciphers may also be obtained using "ssh -Q
243 cipher".
244 ClearAllForwardings
246 Specifies that all local, remote, and dynamic port forwardings
247 specified in the configuration files or on the command line be
248 cleared. This option is primarily useful when used from the
249 ssh(1) command line to clear port forwardings set in configura‐
250 tion files, and is automatically set by scp(1) and sftp(1). The
251 argument must be yes or no (the default).
252 Compression
254 Specifies whether to use compression. The argument must be yes
255 or no (the default).
256 ConnectionAttempts
258 Specifies the number of tries (one per second) to make before
259 exiting. The argument must be an integer. This may be useful in
260 scripts if the connection sometimes fails. The default is 1.
261 ConnectTimeout
263 Specifies the timeout (in seconds) used when connecting to the
264 SSH server, instead of using the default system TCP timeout.
265 This timeout is applied both to establishing the connection and
266 to performing the initial SSH protocol handshake and key
267 exchange.
268 ControlMaster
270 Enables the sharing of multiple sessions over a single network
271 connection. When set to yes, ssh(1) will listen for connections
272 on a control socket specified using the ControlPath argument.
273 Additional sessions can connect to this socket using the same
274 ControlPath with ControlMaster set to no (the default). These
275 sessions will try to reuse the master instance's network connec‐
276 tion rather than initiating new ones, but will fall back to con‐
277 necting normally if the control socket does not exist, or is not
278 listening.
279 Setting this to ask will cause ssh(1) to listen for control con‐
281 nections, but require confirmation using ssh-askpass(1). If the
282 ControlPath cannot be opened, ssh(1) will continue without con‐
283 necting to a master instance.
284 X11 and ssh-agent(1) forwarding is supported over these multi‐
286 plexed connections, however the display and agent forwarded will
287 be the one belonging to the master connection i.e. it is not pos‐
288 sible to forward multiple displays or agents.
289 Two additional options allow for opportunistic multiplexing: try
291 to use a master connection but fall back to creating a new one if
292 one does not already exist. These options are: auto and autoask.
293 The latter requires confirmation like the ask option.
294 ControlPath
296 Specify the path to the control socket used for connection shar‐
297 ing as described in the ControlMaster section above or the string
298 none to disable connection sharing. Arguments to ControlPath may
299 use the tilde syntax to refer to a user's home directory, the
300 tokens described in the TOKENS section and environment variables
301 as described in the ENVIRONMENT VARIABLES section. It is recom‐
302 mended that any ControlPath used for opportunistic connection
303 sharing include at least %h, %p, and %r (or alternatively %C) and
304 be placed in a directory that is not writable by other users.
305 This ensures that shared connections are uniquely identified.
306 ControlPersist
308 When used in conjunction with ControlMaster, specifies that the
309 master connection should remain open in the background (waiting
310 for future client connections) after the initial client connec‐
311 tion has been closed. If set to no (the default), then the mas‐
312 ter connection will not be placed into the background, and will
313 close as soon as the initial client connection is closed. If set
314 to yes or 0, then the master connection will remain in the back‐
315 ground indefinitely (until killed or closed via a mechanism such
316 as the "ssh -O exit"). If set to a time in seconds, or a time in
317 any of the formats documented in sshd_config(5), then the back‐
318 grounded master connection will automatically terminate after it
319 has remained idle (with no client connections) for the specified
320 time.
321 DynamicForward
323 Specifies that a TCP port on the local machine be forwarded over
324 the secure channel, and the application protocol is then used to
325 determine where to connect to from the remote machine.
326 The argument must be [bind_address:]port. IPv6 addresses can be
328 specified by enclosing addresses in square brackets. By default,
329 the local port is bound in accordance with the GatewayPorts set‐
330 ting. However, an explicit bind_address may be used to bind the
331 connection to a specific address. The bind_address of localhost
332 indicates that the listening port be bound for local use only,
333 while an empty address or ‘*’ indicates that the port should be
334 available from all interfaces.
335 Currently the SOCKS4 and SOCKS5 protocols are supported, and
337 ssh(1) will act as a SOCKS server. Multiple forwardings may be
338 specified, and additional forwardings can be given on the command
339 line. Only the superuser can forward privileged ports.
340 EnableSSHKeysign
342 Setting this option to yes in the global client configuration
343 file /etc/ssh/ssh_config enables the use of the helper program
344 ssh-keysign(8) during HostbasedAuthentication. The argument must
345 be yes or no (the default). This option should be placed in the
346 non-hostspecific section. See ssh-keysign(8) for more informa‐
347 tion.
348 EscapeChar
350 Sets the escape character (default: ‘~’). The escape character
351 can also be set on the command line. The argument should be a
352 single character, ‘^’ followed by a letter, or none to disable
353 the escape character entirely (making the connection transparent
354 for binary data).
355 ExitOnForwardFailure
357 Specifies whether ssh(1) should terminate the connection if it
358 cannot set up all requested dynamic, tunnel, local, and remote
359 port forwardings, (e.g. if either end is unable to bind and lis‐
360 ten on a specified port). Note that ExitOnForwardFailure does
361 not apply to connections made over port forwardings and will not,
362 for example, cause ssh(1) to exit if TCP connections to the ulti‐
363 mate forwarding destination fail. The argument must be yes or no
364 (the default).
365 FingerprintHash
367 Specifies the hash algorithm used when displaying key finger‐
368 prints. Valid options are: md5 and sha256 (the default).
369 ForwardAgent
371 Specifies whether the connection to the authentication agent (if
372 any) will be forwarded to the remote machine. The argument may
373 be yes, no (the default), an explicit path to an agent socket or
374 the name of an environment variable (beginning with ‘$’) in which
375 to find the path.
376 Agent forwarding should be enabled with caution. Users with the
378 ability to bypass file permissions on the remote host (for the
379 agent's Unix-domain socket) can access the local agent through
380 the forwarded connection. An attacker cannot obtain key material
381 from the agent, however they can perform operations on the keys
382 that enable them to authenticate using the identities loaded into
383 the agent.
384 ForwardX11
386 Specifies whether X11 connections will be automatically redi‐
387 rected over the secure channel and DISPLAY set. The argument
388 must be yes or no (the default).
389 X11 forwarding should be enabled with caution. Users with the
391 ability to bypass file permissions on the remote host (for the
392 user's X11 authorization database) can access the local X11 dis‐
393 play through the forwarded connection. An attacker may then be
394 able to perform activities such as keystroke monitoring if the
395 ForwardX11Trusted option is also enabled.
396 ForwardX11Timeout
398 Specify a timeout for untrusted X11 forwarding using the format
399 described in the TIME FORMATS section of sshd_config(5). X11
400 connections received by ssh(1) after this time will be refused.
401 Setting ForwardX11Timeout to zero will disable the timeout and
402 permit X11 forwarding for the life of the connection. The
403 default is to disable untrusted X11 forwarding after twenty min‐
404 utes has elapsed.
405 ForwardX11Trusted
407 If this option is set to yes, remote X11 clients will have full
408 access to the original X11 display.
409 If this option is set to no (the default), remote X11 clients
411 will be considered untrusted and prevented from stealing or tam‐
412 pering with data belonging to trusted X11 clients. Furthermore,
413 the xauth(1) token used for the session will be set to expire
414 after 20 minutes. Remote clients will be refused access after
415 this time.
416 See the X11 SECURITY extension specification for full details on
418 the restrictions imposed on untrusted clients.
419 GatewayPorts
421 Specifies whether remote hosts are allowed to connect to local
422 forwarded ports. By default, ssh(1) binds local port forwardings
423 to the loopback address. This prevents other remote hosts from
424 connecting to forwarded ports. GatewayPorts can be used to spec‐
425 ify that ssh should bind local port forwardings to the wildcard
426 address, thus allowing remote hosts to connect to forwarded
427 ports. The argument must be yes or no (the default).
428 GlobalKnownHostsFile
430 Specifies one or more files to use for the global host key data‐
431 base, separated by whitespace. The default is
432 /etc/ssh/ssh_known_hosts, /etc/ssh/ssh_known_hosts2.
433 GSSAPIAuthentication
435 Specifies whether user authentication based on GSSAPI is allowed.
436 The default is no.
437 GSSAPIClientIdentity
439 If set, specifies the GSSAPI client identity that ssh should use
440 when connecting to the server. The default is unset, which means
441 that the default identity will be used.
442 GSSAPIDelegateCredentials
444 Forward (delegate) credentials to the server. The default is no.
445 GSSAPIKeyExchange
447 Specifies whether key exchange based on GSSAPI may be used. When
448 using GSSAPI key exchange the server need not have a host key.
449 The default is “no”.
450 GSSAPIRenewalForcesRekey
452 If set to “yes” then renewal of the client's GSSAPI credentials
453 will force the rekeying of the ssh connection. With a compatible
454 server, this will delegate the renewed credentials to a session
455 on the server.
456 Checks are made to ensure that credentials are only propagated
458 when the new credentials match the old ones on the originating
459 client and where the receiving server still has the old set in
460 its cache.
461 The default is “no”.
463 For this to work GSSAPIKeyExchange needs to be enabled in the
465 server and also used by the client.
466 GSSAPIServerIdentity
468 If set, specifies the GSSAPI server identity that ssh should
469 expect when connecting to the server. The default is unset, which
470 means that the expected GSSAPI server identity will be determined
471 from the target hostname.
472 GSSAPITrustDns
474 Set to “yes” to indicate that the DNS is trusted to securely
475 canonicalize the name of the host being connected to. If “no”,
476 the hostname entered on the command line will be passed untouched
477 to the GSSAPI library. The default is “no”.
478 GSSAPIKexAlgorithms
480 The default is handled system-wide by crypto-policies(7). To see
481 the defaults and how to modify this default, see manual page
482 update-crypto-policies(8).
483 The list of key exchange algorithms that are offered for GSSAPI
485 key exchange. Possible values are
486 gss-gex-sha1-,
488 gss-group1-sha1-,
489 gss-group14-sha1-,
490 gss-group14-sha256-,
491 gss-group16-sha512-,
492 gss-nistp256-sha256-,
493 gss-curve25519-sha256-
494 This option only applies to connections using GSSAPI.
496 HashKnownHosts
498 Indicates that ssh(1) should hash host names and addresses when
499 they are added to ~/.ssh/known_hosts. These hashed names may be
500 used normally by ssh(1) and sshd(8), but they do not visually
501 reveal identifying information if the file's contents are dis‐
502 closed. The default is no. Note that existing names and
503 addresses in known hosts files will not be converted automati‐
504 cally, but may be manually hashed using ssh-keygen(1).
505 HostbasedAuthentication
507 Specifies whether to try rhosts based authentication with public
508 key authentication. The argument must be yes or no (the
509 default).
510 HostbasedKeyTypes
512 Specifies the key types that will be used for hostbased authenti‐
513 cation as a comma-separated list of patterns. Alternately if the
514 specified list begins with a ‘+’ character, then the specified
515 key types will be appended to the default set instead of replac‐
516 ing them. If the specified list begins with a ‘-’ character,
517 then the specified key types (including wildcards) will be
518 removed from the default set instead of replacing them. If the
519 specified list begins with a ‘^’ character, then the specified
520 key types will be placed at the head of the default set. The
521 default for this option is:
522 ecdsa-sha2-nistp256-cert-v01@openssh.com,
524 ecdsa-sha2-nistp384-cert-v01@openssh.com,
525 ecdsa-sha2-nistp521-cert-v01@openssh.com,
526 sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
527 ssh-ed25519-cert-v01@openssh.com,
528 sk-ssh-ed25519-cert-v01@openssh.com,
529 rsa-sha2-512-cert-v01@openssh.com,
530 rsa-sha2-256-cert-v01@openssh.com,
531 ssh-rsa-cert-v01@openssh.com,
532 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
533 sk-ecdsa-sha2-nistp256@openssh.com,
534 ssh-ed25519,sk-ssh-ed25519@openssh.com,
535 rsa-sha2-512,rsa-sha2-256,ssh-rsa
536 The -Q option of ssh(1) may be used to list supported key types.
538 HostKeyAlgorithms
540 Specifies the host key algorithms that the client wants to use in
541 order of preference. Alternately if the specified list begins
542 with a ‘+’ character, then the specified key types will be
543 appended to the default set instead of replacing them. If the
544 specified list begins with a ‘-’ character, then the specified
545 key types (including wildcards) will be removed from the default
546 set instead of replacing them. If the specified list begins with
547 a ‘^’ character, then the specified key types will be placed at
548 the head of the default set. The default for this option is:
549 ecdsa-sha2-nistp256-cert-v01@openssh.com,
551 ecdsa-sha2-nistp384-cert-v01@openssh.com,
552 ecdsa-sha2-nistp521-cert-v01@openssh.com,
553 sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
554 ssh-ed25519-cert-v01@openssh.com,
555 sk-ssh-ed25519-cert-v01@openssh.com,
556 rsa-sha2-512-cert-v01@openssh.com,
557 rsa-sha2-256-cert-v01@openssh.com,
558 ssh-rsa-cert-v01@openssh.com,
559 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
560 sk-ecdsa-sha2-nistp256@openssh.com,
561 ssh-ed25519,sk-ssh-ed25519@openssh.com,
562 rsa-sha2-512,rsa-sha2-256,ssh-rsa
563 If hostkeys are known for the destination host then this default
565 is modified to prefer their algorithms.
566 The list of available key types may also be obtained using "ssh
568 -Q HostKeyAlgorithms".
569 HostKeyAlias
571 Specifies an alias that should be used instead of the real host
572 name when looking up or saving the host key in the host key data‐
573 base files and when validating host certificates. This option is
574 useful for tunneling SSH connections or for multiple servers run‐
575 ning on a single host.
576 Hostname
578 Specifies the real host name to log into. This can be used to
579 specify nicknames or abbreviations for hosts. Arguments to
580 Hostname accept the tokens described in the TOKENS section.
581 Numeric IP addresses are also permitted (both on the command line
582 and in Hostname specifications). The default is the name given
583 on the command line.
584 IdentitiesOnly
586 Specifies that ssh(1) should only use the configured authentica‐
587 tion identity and certificate files (either the default files, or
588 those explicitly configured in the ssh_config files or passed on
589 the ssh(1) command-line), even if ssh-agent(1) or a
590 PKCS11Provider or SecurityKeyProvider offers more identities.
591 The argument to this keyword must be yes or no (the default).
592 This option is intended for situations where ssh-agent offers
593 many different identities.
594 IdentityAgent
596 Specifies the UNIX-domain socket used to communicate with the
597 authentication agent.
598 This option overrides the SSH_AUTH_SOCK environment variable and
600 can be used to select a specific agent. Setting the socket name
601 to none disables the use of an authentication agent. If the
602 string "SSH_AUTH_SOCK" is specified, the location of the socket
603 will be read from the SSH_AUTH_SOCK environment variable. Other‐
604 wise if the specified value begins with a ‘$’ character, then it
605 will be treated as an environment variable containing the loca‐
606 tion of the socket.
607 Arguments to IdentityAgent may use the tilde syntax to refer to a
609 user's home directory, the tokens described in the TOKENS section
610 and environment variables as described in the ENVIRONMENT
611 VARIABLES section.
612 IdentityFile
614 Specifies a file from which the user's DSA, ECDSA, authenticator-
615 hosted ECDSA, Ed25519, authenticator-hosted Ed25519 or RSA
616 authentication identity is read. The default is ~/.ssh/id_dsa,
617 ~/.ssh/id_ecdsa, ~/.ssh/id_ecdsa_sk, ~/.ssh/id_ed25519,
618 ~/.ssh/id_ed25519_sk and ~/.ssh/id_rsa. Additionally, any iden‐
619 tities represented by the authentication agent will be used for
620 authentication unless IdentitiesOnly is set. If no certificates
621 have been explicitly specified by CertificateFile, ssh(1) will
622 try to load certificate information from the filename obtained by
623 appending -cert.pub to the path of a specified IdentityFile.
624 Arguments to IdentityFile may use the tilde syntax to refer to a
626 user's home directory or the tokens described in the TOKENS sec‐
627 tion.
628 It is possible to have multiple identity files specified in con‐
630 figuration files; all these identities will be tried in sequence.
631 Multiple IdentityFile directives will add to the list of identi‐
632 ties tried (this behaviour differs from that of other configura‐
633 tion directives).
634 IdentityFile may be used in conjunction with IdentitiesOnly to
636 select which identities in an agent are offered during authenti‐
637 cation. IdentityFile may also be used in conjunction with
638 CertificateFile in order to provide any certificate also needed
639 for authentication with the identity.
640 The authentication identity can be also specified in a form of
642 PKCS#11 URI starting with a string pkcs11:. There is supported a
643 subset of the PKCS#11 URI as defined in RFC 7512 (implemented
644 path arguments id, manufacturer, object, token and query argu‐
645 ments module-path and pin-value ). The URI can not be in quotes.
646 IgnoreUnknown
648 Specifies a pattern-list of unknown options to be ignored if they
649 are encountered in configuration parsing. This may be used to
650 suppress errors if ssh_config contains options that are unrecog‐
651 nised by ssh(1). It is recommended that IgnoreUnknown be listed
652 early in the configuration file as it will not be applied to
653 unknown options that appear before it.
654 Include
656 Include the specified configuration file(s). Multiple pathnames
657 may be specified and each pathname may contain glob(7) wildcards
658 and, for user configurations, shell-like ‘~’ references to user
659 home directories. Wildcards will be expanded and processed in
660 lexical order. Files without absolute paths are assumed to be in
661 ~/.ssh if included in a user configuration file or /etc/ssh if
662 included from the system configuration file. Include directive
663 may appear inside a Match or Host block to perform conditional
664 inclusion.
665 IPQoS Specifies the IPv4 type-of-service or DSCP class for connections.
667 Accepted values are af11, af12, af13, af21, af22, af23, af31,
668 af32, af33, af41, af42, af43, cs0, cs1, cs2, cs3, cs4, cs5, cs6,
669 cs7, ef, le, lowdelay, throughput, reliability, a numeric value,
670 or none to use the operating system default. This option may
671 take one or two arguments, separated by whitespace. If one argu‐
672 ment is specified, it is used as the packet class uncondition‐
673 ally. If two values are specified, the first is automatically
674 selected for interactive sessions and the second for non-interac‐
675 tive sessions. The default is af21 (Low-Latency Data) for inter‐
676 active sessions and cs1 (Lower Effort) for non-interactive ses‐
677 sions.
678 KbdInteractiveAuthentication
680 Specifies whether to use keyboard-interactive authentication.
681 The argument to this keyword must be yes (the default) or no.
682 KbdInteractiveDevices
684 Specifies the list of methods to use in keyboard-interactive
685 authentication. Multiple method names must be comma-separated.
686 The default is to use the server specified list. The methods
687 available vary depending on what the server supports. For an
688 OpenSSH server, it may be zero or more of: bsdauth and pam.
689 KexAlgorithms
691 The default is handled system-wide by crypto-policies(7). To see
692 the defaults and how to modify this default, see manual page
693 update-crypto-policies(8).
694 Specifies the available KEX (Key Exchange) algorithms. Multiple
696 algorithms must be comma-separated. If the specified list begins
697 with a ‘+’ character, then the specified methods will be appended
698 to the built-in openssh default set instead of replacing them.
699 If the specified list begins with a ‘-’ character, then the spec‐
700 ified methods (including wildcards) will be removed from the
701 built-in openssh default set instead of replacing them. If the
702 specified list begins with a ‘^’ character, then the specified
703 methods will be placed at the head of the built-in openssh
704 default set.
705 The list of available key exchange algorithms may also be
707 obtained using "ssh -Q kex".
708 LocalCommand
710 Specifies a command to execute on the local machine after suc‐
711 cessfully connecting to the server. The command string extends
712 to the end of the line, and is executed with the user's shell.
713 Arguments to LocalCommand accept the tokens described in the
714 TOKENS section.
715 The command is run synchronously and does not have access to the
717 session of the ssh(1) that spawned it. It should not be used for
718 interactive commands.
719 This directive is ignored unless PermitLocalCommand has been
721 enabled.
722 LocalForward
724 Specifies that a TCP port on the local machine be forwarded over
725 the secure channel to the specified host and port from the remote
726 machine. The first argument specifies the listener and may be
727 [bind_address:]port or a Unix domain socket path. The second
728 argument is the destination and may be host:hostport or a Unix
729 domain socket path if the remote host supports it.
730 IPv6 addresses can be specified by enclosing addresses in square
732 brackets. Multiple forwardings may be specified, and additional
733 forwardings can be given on the command line. Only the superuser
734 can forward privileged ports. By default, the local port is
735 bound in accordance with the GatewayPorts setting. However, an
736 explicit bind_address may be used to bind the connection to a
737 specific address. The bind_address of localhost indicates that
738 the listening port be bound for local use only, while an empty
739 address or ‘*’ indicates that the port should be available from
740 all interfaces. Unix domain socket paths may use the tokens
741 described in the TOKENS section and environment variables as
742 described in the ENVIRONMENT VARIABLES section.
743 LogLevel
745 Gives the verbosity level that is used when logging messages from
746 ssh(1). The possible values are: QUIET, FATAL, ERROR, INFO, VER‐
747 BOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO.
748 DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify
749 higher levels of verbose output.
750 MACs The default is handled system-wide by crypto-policies(7). To see
752 the defaults and how to modify this default, see manual page
753 update-crypto-policies(8).
754 Specifies the MAC (message authentication code) algorithms in
756 order of preference. The MAC algorithm is used for data
757 integrity protection. Multiple algorithms must be comma-sepa‐
758 rated. If the specified list begins with a ‘+’ character, then
759 the specified algorithms will be appended to the built-in openssh
760 default set instead of replacing them. If the specified list
761 begins with a ‘-’ character, then the specified algorithms
762 (including wildcards) will be removed from the built-in openssh
763 default set instead of replacing them. If the specified list
764 begins with a ‘^’ character, then the specified algorithms will
765 be placed at the head of the built-in openssh default set.
766 The algorithms that contain "-etm" calculate the MAC after
768 encryption (encrypt-then-mac). These are considered safer and
769 their use recommended.
770 The list of available MAC algorithms may also be obtained using
772 "ssh -Q mac".
773 NoHostAuthenticationForLocalhost
775 Disable host authentication for localhost (loopback addresses).
776 The argument to this keyword must be yes or no (the default).
777 NumberOfPasswordPrompts
779 Specifies the number of password prompts before giving up. The
780 argument to this keyword must be an integer. The default is 3.
781 PasswordAuthentication
783 Specifies whether to use password authentication. The argument
784 to this keyword must be yes (the default) or no.
785 PermitLocalCommand
787 Allow local command execution via the LocalCommand option or
788 using the !command escape sequence in ssh(1). The argument must
789 be yes or no (the default).
790 PKCS11Provider
792 Specifies which PKCS#11 provider to use or none to indicate that
793 no provider should be used (the default). The argument to this
794 keyword is a path to the PKCS#11 shared library ssh(1) should use
795 to communicate with a PKCS#11 token providing keys for user
796 authentication.
797 Port Specifies the port number to connect on the remote host. The
799 default is 22.
800 PreferredAuthentications
802 Specifies the order in which the client should try authentication
803 methods. This allows a client to prefer one method (e.g.
804 keyboard-interactive) over another method (e.g. password). The
805 default is:
806 gssapi-with-mic,hostbased,publickey,
808 keyboard-interactive,password
809 ProxyCommand
811 Specifies the command to use to connect to the server. The com‐
812 mand string extends to the end of the line, and is executed using
813 the user's shell ‘exec’ directive to avoid a lingering shell
814 process.
815 Arguments to ProxyCommand accept the tokens described in the
817 TOKENS section. The command can be basically anything, and
818 should read from its standard input and write to its standard
819 output. It should eventually connect an sshd(8) server running
820 on some machine, or execute sshd -i somewhere. Host key manage‐
821 ment will be done using the Hostname of the host being connected
822 (defaulting to the name typed by the user). Setting the command
823 to none disables this option entirely. Note that CheckHostIP is
824 not available for connects with a proxy command.
825 This directive is useful in conjunction with nc(1) and its proxy
827 support. For example, the following directive would connect via
828 an HTTP proxy at 192.0.2.0:
829 ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
831 ProxyJump
833 Specifies one or more jump proxies as either [user@]host[:port]
834 or an ssh URI. Multiple proxies may be separated by comma char‐
835 acters and will be visited sequentially. Setting this option
836 will cause ssh(1) to connect to the target host by first making a
837 ssh(1) connection to the specified ProxyJump host and then estab‐
838 lishing a TCP forwarding to the ultimate target from there.
839 Note that this option will compete with the ProxyCommand option -
841 whichever is specified first will prevent later instances of the
842 other from taking effect.
843 Note also that the configuration for the destination host (either
845 supplied via the command-line or the configuration file) is not
846 generally applied to jump hosts. ~/.ssh/config should be used if
847 specific configuration is required for jump hosts.
848 ProxyUseFdpass
850 Specifies that ProxyCommand will pass a connected file descriptor
851 back to ssh(1) instead of continuing to execute and pass data.
852 The default is no.
853 PubkeyAcceptedKeyTypes
855 The default is handled system-wide by crypto-policies(7). To see
856 the defaults and how to modify this default, see manual page
857 update-crypto-policies(8).
858 Specifies the key types that will be used for public key authen‐
860 tication as a comma-separated list of patterns. If the specified
861 list begins with a ‘+’ character, then the key types after it
862 will be appended to the built-in openssh default instead of
863 replacing it. If the specified list begins with a ‘-’ character,
864 then the specified key types (including wildcards) will be
865 removed from the built-in openssh default set instead of replac‐
866 ing them. If the specified list begins with a ‘^’ character,
867 then the specified key types will be placed at the head of the
868 built-in openssh default set.
869 The list of available key types may also be obtained using "ssh
871 -Q PubkeyAcceptedKeyTypes".
872 PubkeyAuthentication
874 Specifies whether to try public key authentication. The argument
875 to this keyword must be yes (the default) or no.
876 RekeyLimit
878 Specifies the maximum amount of data that may be transmitted
879 before the session key is renegotiated, optionally followed a
880 maximum amount of time that may pass before the session key is
881 renegotiated. The first argument is specified in bytes and may
882 have a suffix of ‘K’, ‘M’, or ‘G’ to indicate Kilobytes,
883 Megabytes, or Gigabytes, respectively. The default is between
884 ‘1G’ and ‘4G’, depending on the cipher. The optional second
885 value is specified in seconds and may use any of the units docu‐
886 mented in the TIME FORMATS section of sshd_config(5). The
887 default value for RekeyLimit is default none, which means that
888 rekeying is performed after the cipher's default amount of data
889 has been sent or received and no time based rekeying is done.
890 RemoteCommand
892 Specifies a command to execute on the remote machine after suc‐
893 cessfully connecting to the server. The command string extends
894 to the end of the line, and is executed with the user's shell.
895 Arguments to RemoteCommand accept the tokens described in the
896 TOKENS section.
897 RemoteForward
899 Specifies that a TCP port on the remote machine be forwarded over
900 the secure channel. The remote port may either be forwarded to a
901 specified host and port from the local machine, or may act as a
902 SOCKS 4/5 proxy that allows a remote client to connect to arbi‐
903 trary destinations from the local machine. The first argument is
904 the listening specification and may be [bind_address:]port or, if
905 the remote host supports it, a Unix domain socket path. If for‐
906 warding to a specific destination then the second argument must
907 be host:hostport or a Unix domain socket path, otherwise if no
908 destination argument is specified then the remote forwarding will
909 be established as a SOCKS proxy.
910 IPv6 addresses can be specified by enclosing addresses in square
912 brackets. Multiple forwardings may be specified, and additional
913 forwardings can be given on the command line. Privileged ports
914 can be forwarded only when logging in as root on the remote
915 machine. Unix domain socket paths may use the tokens described
916 in the TOKENS section and environment variables as described in
917 the ENVIRONMENT VARIABLES section.
918 If the port argument is 0, the listen port will be dynamically
920 allocated on the server and reported to the client at run time.
921 If the bind_address is not specified, the default is to only bind
923 to loopback addresses. If the bind_address is ‘*’ or an empty
924 string, then the forwarding is requested to listen on all inter‐
925 faces. Specifying a remote bind_address will only succeed if the
926 server's GatewayPorts option is enabled (see sshd_config(5)).
927 RequestTTY
929 Specifies whether to request a pseudo-tty for the session. The
930 argument may be one of: no (never request a TTY), yes (always
931 request a TTY when standard input is a TTY), force (always
932 request a TTY) or auto (request a TTY when opening a login ses‐
933 sion). This option mirrors the -t and -T flags for ssh(1).
934 RevokedHostKeys
936 Specifies revoked host public keys. Keys listed in this file
937 will be refused for host authentication. Note that if this file
938 does not exist or is not readable, then host authentication will
939 be refused for all hosts. Keys may be specified as a text file,
940 listing one public key per line, or as an OpenSSH Key Revocation
941 List (KRL) as generated by ssh-keygen(1). For more information
942 on KRLs, see the KEY REVOCATION LISTS section in ssh-keygen(1).
943 SecurityKeyProvider
945 Specifies a path to a library that will be used when loading any
946 FIDO authenticator-hosted keys, overriding the default of using
947 the built-in USB HID support.
948 If the specified value begins with a ‘$’ character, then it will
950 be treated as an environment variable containing the path to the
951 library.
952 SendEnv
954 Specifies what variables from the local environ(7) should be sent
955 to the server. The server must also support it, and the server
956 must be configured to accept these environment variables. Note
957 that the TERM environment variable is always sent whenever a
958 pseudo-terminal is requested as it is required by the protocol.
959 Refer to AcceptEnv in sshd_config(5) for how to configure the
960 server. Variables are specified by name, which may contain wild‐
961 card characters. Multiple environment variables may be separated
962 by whitespace or spread across multiple SendEnv directives.
963 See PATTERNS for more information on patterns.
965 It is possible to clear previously set SendEnv variable names by
967 prefixing patterns with -. The default is not to send any envi‐
968 ronment variables.
969 ServerAliveCountMax
971 Sets the number of server alive messages (see below) which may be
972 sent without ssh(1) receiving any messages back from the server.
973 If this threshold is reached while server alive messages are
974 being sent, ssh will disconnect from the server, terminating the
975 session. It is important to note that the use of server alive
976 messages is very different from TCPKeepAlive (below). The server
977 alive messages are sent through the encrypted channel and there‐
978 fore will not be spoofable. The TCP keepalive option enabled by
979 TCPKeepAlive is spoofable. The server alive mechanism is valu‐
980 able when the client or server depend on knowing when a connec‐
981 tion has become unresponsive.
982 The default value is 3. If, for example, ServerAliveInterval
984 (see below) is set to 15 and ServerAliveCountMax is left at the
985 default, if the server becomes unresponsive, ssh will disconnect
986 after approximately 45 seconds.
987 ServerAliveInterval
989 Sets a timeout interval in seconds after which if no data has
990 been received from the server, ssh(1) will send a message through
991 the encrypted channel to request a response from the server. The
992 default is 0, indicating that these messages will not be sent to
993 the server.
994 SetEnv Directly specify one or more environment variables and their con‐
996 tents to be sent to the server. Similarly to SendEnv, the server
997 must be prepared to accept the environment variable.
998 StreamLocalBindMask
1000 Sets the octal file creation mode mask (umask) used when creating
1001 a Unix-domain socket file for local or remote port forwarding.
1002 This option is only used for port forwarding to a Unix-domain
1003 socket file.
1004 The default value is 0177, which creates a Unix-domain socket
1006 file that is readable and writable only by the owner. Note that
1007 not all operating systems honor the file mode on Unix-domain
1008 socket files.
1009 StreamLocalBindUnlink
1011 Specifies whether to remove an existing Unix-domain socket file
1012 for local or remote port forwarding before creating a new one.
1013 If the socket file already exists and StreamLocalBindUnlink is
1014 not enabled, ssh will be unable to forward the port to the Unix-
1015 domain socket file. This option is only used for port forwarding
1016 to a Unix-domain socket file.
1017 The argument must be yes or no (the default).
1019 StrictHostKeyChecking
1021 If this flag is set to yes, ssh(1) will never automatically add
1022 host keys to the ~/.ssh/known_hosts file, and refuses to connect
1023 to hosts whose host key has changed. This provides maximum pro‐
1024 tection against man-in-the-middle (MITM) attacks, though it can
1025 be annoying when the /etc/ssh/ssh_known_hosts file is poorly
1026 maintained or when connections to new hosts are frequently made.
1027 This option forces the user to manually add all new hosts.
1028 If this flag is set to “accept-new” then ssh will automatically
1030 add new host keys to the user known hosts files, but will not
1031 permit connections to hosts with changed host keys. If this flag
1032 is set to “no” or “off”, ssh will automatically add new host keys
1033 to the user known hosts files and allow connections to hosts with
1034 changed hostkeys to proceed, subject to some restrictions. If
1035 this flag is set to ask (the default), new host keys will be
1036 added to the user known host files only after the user has con‐
1037 firmed that is what they really want to do, and ssh will refuse
1038 to connect to hosts whose host key has changed. The host keys of
1039 known hosts will be verified automatically in all cases.
1040 SyslogFacility
1042 Gives the facility code that is used when logging messages from
1043 ssh(1). The possible values are: DAEMON, USER, AUTH, LOCAL0,
1044 LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The
1045 default is USER.
1046 TCPKeepAlive
1048 Specifies whether the system should send TCP keepalive messages
1049 to the other side. If they are sent, death of the connection or
1050 crash of one of the machines will be properly noticed. However,
1051 this means that connections will die if the route is down tempo‐
1052 rarily, and some people find it annoying.
1053 The default is yes (to send TCP keepalive messages), and the
1055 client will notice if the network goes down or the remote host
1056 dies. This is important in scripts, and many users want it too.
1057 To disable TCP keepalive messages, the value should be set to no.
1059 See also ServerAliveInterval for protocol-level keepalives.
1060 Tunnel Request tun(4) device forwarding between the client and the
1062 server. The argument must be yes, point-to-point (layer 3),
1063 ethernet (layer 2), or no (the default). Specifying yes requests
1064 the default tunnel mode, which is point-to-point.
1065 TunnelDevice
1067 Specifies the tun(4) devices to open on the client (local_tun)
1068 and the server (remote_tun).
1069 The argument must be local_tun[:remote_tun]. The devices may be
1071 specified by numerical ID or the keyword any, which uses the next
1072 available tunnel device. If remote_tun is not specified, it
1073 defaults to any. The default is any:any.
1074 UpdateHostKeys
1076 Specifies whether ssh(1) should accept notifications of addi‐
1077 tional hostkeys from the server sent after authentication has
1078 completed and add them to UserKnownHostsFile. The argument must
1079 be yes, no or ask. This option allows learning alternate
1080 hostkeys for a server and supports graceful key rotation by
1081 allowing a server to send replacement public keys before old ones
1082 are removed. Additional hostkeys are only accepted if the key
1083 used to authenticate the host was already trusted or explicitly
1084 accepted by the user.
1085 UpdateHostKeys is enabled by default if the user has not overrid‐
1087 den the default UserKnownHostsFile setting, otherwise
1088 UpdateHostKeys will be set to ask.
1089 If UpdateHostKeys is set to ask, then the user is asked to con‐
1091 firm the modifications to the known_hosts file. Confirmation is
1092 currently incompatible with ControlPersist, and will be disabled
1093 if it is enabled.
1094 Presently, only sshd(8) from OpenSSH 6.8 and greater support the
1096 "hostkeys@openssh.com" protocol extension used to inform the
1097 client of all the server's hostkeys.
1098 User Specifies the user to log in as. This can be useful when a dif‐
1100 ferent user name is used on different machines. This saves the
1101 trouble of having to remember to give the user name on the com‐
1102 mand line.
1103 UserKnownHostsFile
1105 Specifies one or more files to use for the user host key data‐
1106 base, separated by whitespace. Each filename may use tilde nota‐
1107 tion to refer to the user's home directory, the tokens described
1108 in the TOKENS section and environment variables as described in
1109 the ENVIRONMENT VARIABLES section. The default is
1110 ~/.ssh/known_hosts, ~/.ssh/known_hosts2.
1111 VerifyHostKeyDNS
1113 Specifies whether to verify the remote key using DNS and SSHFP
1114 resource records. If this option is set to yes, the client will
1115 implicitly trust keys that match a secure fingerprint from DNS.
1116 Insecure fingerprints will be handled as if this option was set
1117 to ask. If this option is set to ask, information on fingerprint
1118 match will be displayed, but the user will still need to confirm
1119 new host keys according to the StrictHostKeyChecking option. The
1120 default is no.
1121 See also VERIFYING HOST KEYS in ssh(1).
1123 VisualHostKey
1125 If this flag is set to yes, an ASCII art representation of the
1126 remote host key fingerprint is printed in addition to the finger‐
1127 print string at login and for unknown host keys. If this flag is
1128 set to no (the default), no fingerprint strings are printed at
1129 login and only the fingerprint string will be printed for unknown
1130 host keys.
1131 XAuthLocation
1133 Specifies the full pathname of the xauth(1) program. The default
1134 is /usr/bin/xauth.
1135
1137 A pattern consists of zero or more non-whitespace characters, ‘*’ (a
1138 wildcard that matches zero or more characters), or ‘?’ (a wildcard that
1139 matches exactly one character). For example, to specify a set of decla‐
1140 rations for any host in the ".co.uk" set of domains, the following pat‐
1141 tern could be used:
1142 Host *.co.uk
1144 The following pattern would match any host in the 192.168.0.[0-9] network
1146 range:
1147 Host 192.168.0.?
1149 A pattern-list is a comma-separated list of patterns. Patterns within
1151 pattern-lists may be negated by preceding them with an exclamation mark
1152 (‘!’). For example, to allow a key to be used from anywhere within an
1153 organization except from the "dialup" pool, the following entry (in
1154 authorized_keys) could be used:
1155 from="!*.dialup.example.com,*.example.com"
1157 Note that a negated match will never produce a positive result by itself.
1159 For example, attempting to match "host3" against the following pattern-
1160 list will fail:
1161 from="!host1,!host2"
1163 The solution here is to include a term that will yield a positive match,
1165 such as a wildcard:
1166 from="!host1,!host2,*"
1168
1170 Arguments to some keywords can make use of tokens, which are expanded at
1171 runtime:
1172 %% A literal ‘%’.
1174 %C Hash of %l%h%p%r.
1175 %d Local user's home directory.
1176 %h The remote hostname.
1177 %i The local user ID.
1178 %k The host key alias if specified, otherwise the orignal remote
1179 hostname given on the command line.
1180 %L The local hostname.
1181 %l The local hostname, including the domain name.
1182 %n The original remote hostname, as given on the command line.
1183 %p The remote port.
1184 %r The remote username.
1185 %T The local tun(4) or tap(4) network interface assigned if tun‐
1186 nel forwarding was requested, or "NONE" otherwise.
1187 %u The local username.
1188 CertificateFile, ControlPath, IdentityAgent, IdentityFile, LocalForward,
1190 Match exec, RemoteCommand, RemoteForward, and UserKnownHostsFile accept
1191 the tokens %%, %C, %d, %h, %i, %L, %l, %n, %p, %r, and %u.
1192 Hostname accepts the tokens %% and %h.
1194 LocalCommand accepts all tokens.
1196 ProxyCommand accepts the tokens %%, %h, %n, %p, and %r.
1198
1200 Arguments to some keywords can be expanded at runtime from environment
1201 variables on the client by enclosing them in ${}, for example
1202 ${HOME}/.ssh would refer to the user's .ssh directory. If a specified
1203 environment variable does not exist then an error will be returned and
1204 the setting for that keyword will be ignored.
1205 The keywords CertificateFile, ControlPath, IdentityAgent, IdentityFile
1207 and UserKnownHostsFile support environment variables. The keywords
1208 LocalForward and RemoteForward support environment variables only for
1209 Unix domain socket paths.
1210
1212 ~/.ssh/config
1213 This is the per-user configuration file. The format of this file
1214 is described above. This file is used by the SSH client.
1215 Because of the potential for abuse, this file must have strict
1216 permissions: read/write for the user, and not writable by others.
1217 /etc/ssh/ssh_config
1219 Systemwide configuration file. This file provides defaults for
1220 those values that are not specified in the user's configuration
1221 file, and for those users who do not have a configuration file.
1222 This file must be world-readable.
1223
1225 ssh(1)
1226
1228 OpenSSH is a derivative of the original and free ssh 1.2.12 release by
1229 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
1230 de Raadt and Dug Song removed many bugs, re-added newer features and cre‐
1231 ated OpenSSH. Markus Friedl contributed the support for SSH protocol
1232 versions 1.5 and 2.0.
1233BSD August 11, 2020 BSD