1SSHD_CONFIG(5) BSD File Formats Manual SSHD_CONFIG(5)
2
4 sshd_config — OpenSSH daemon configuration file
5
7 sshd(8) reads configuration data from /etc/ssh/sshd_config (or the file
8 specified with -f on the command line). The file contains keyword-argu‐
9 ment pairs, one per line. For each keyword, the first obtained value
10 will be used. Lines starting with ‘#’ and empty lines are interpreted as
11 comments. Arguments may optionally be enclosed in double quotes (") in
12 order to represent arguments containing spaces.
13 The possible keywords and their meanings are as follows (note that key‐
15 words are case-insensitive and arguments are case-sensitive):
16 AcceptEnv
18 Specifies what environment variables sent by the client will be
19 copied into the session's environ(7). See SendEnv and SetEnv in
20 ssh_config(5) for how to configure the client. The TERM environ‐
21 ment variable is always accepted whenever the client requests a
22 pseudo-terminal as it is required by the protocol. Variables are
23 specified by name, which may contain the wildcard characters ‘*’
24 and ‘?’. Multiple environment variables may be separated by
25 whitespace or spread across multiple AcceptEnv directives. Be
26 warned that some environment variables could be used to bypass
27 restricted user environments. For this reason, care should be
28 taken in the use of this directive. The default is not to accept
29 any environment variables.
30 AddressFamily
32 Specifies which address family should be used by sshd(8). Valid
33 arguments are any (the default), inet (use IPv4 only), or inet6
34 (use IPv6 only).
35 AllowAgentForwarding
37 Specifies whether ssh-agent(1) forwarding is permitted. The de‐
38 fault is yes. Note that disabling agent forwarding does not im‐
39 prove security unless users are also denied shell access, as they
40 can always install their own forwarders.
41 AllowGroups
43 This keyword can be followed by a list of group name patterns,
44 separated by spaces. If specified, login is allowed only for
45 users whose primary group or supplementary group list matches one
46 of the patterns. Only group names are valid; a numerical group
47 ID is not recognized. By default, login is allowed for all
48 groups. The allow/deny groups directives are processed in the
49 following order: DenyGroups, AllowGroups.
50 See PATTERNS in ssh_config(5) for more information on patterns.
52 AllowStreamLocalForwarding
54 Specifies whether StreamLocal (Unix-domain socket) forwarding is
55 permitted. The available options are yes (the default) or all to
56 allow StreamLocal forwarding, no to prevent all StreamLocal for‐
57 warding, local to allow local (from the perspective of ssh(1))
58 forwarding only or remote to allow remote forwarding only. Note
59 that disabling StreamLocal forwarding does not improve security
60 unless users are also denied shell access, as they can always in‐
61 stall their own forwarders.
62 AllowTcpForwarding
64 Specifies whether TCP forwarding is permitted. The available op‐
65 tions are yes (the default) or all to allow TCP forwarding, no to
66 prevent all TCP forwarding, local to allow local (from the per‐
67 spective of ssh(1)) forwarding only or remote to allow remote
68 forwarding only. Note that disabling TCP forwarding does not im‐
69 prove security unless users are also denied shell access, as they
70 can always install their own forwarders.
71 AllowUsers
73 This keyword can be followed by a list of user name patterns,
74 separated by spaces. If specified, login is allowed only for
75 user names that match one of the patterns. Only user names are
76 valid; a numerical user ID is not recognized. By default, login
77 is allowed for all users. If the pattern takes the form
78 USER@HOST then USER and HOST are separately checked, restricting
79 logins to particular users from particular hosts. HOST criteria
80 may additionally contain addresses to match in CIDR ad‐
81 dress/masklen format. The allow/deny users directives are pro‐
82 cessed in the following order: DenyUsers, AllowUsers.
83 See PATTERNS in ssh_config(5) for more information on patterns.
85 AuthenticationMethods
87 Specifies the authentication methods that must be successfully
88 completed for a user to be granted access. This option must be
89 followed by one or more lists of comma-separated authentication
90 method names, or by the single string any to indicate the default
91 behaviour of accepting any single authentication method. If the
92 default is overridden, then successful authentication requires
93 completion of every method in at least one of these lists.
94 For example, "publickey,password publickey,keyboard-interactive"
96 would require the user to complete public key authentication,
97 followed by either password or keyboard interactive authentica‐
98 tion. Only methods that are next in one or more lists are of‐
99 fered at each stage, so for this example it would not be possible
100 to attempt password or keyboard-interactive authentication before
101 public key.
102 For keyboard interactive authentication it is also possible to
104 restrict authentication to a specific device by appending a colon
105 followed by the device identifier bsdauth or pam. depending on
106 the server configuration. For example,
107 "keyboard-interactive:bsdauth" would restrict keyboard interac‐
108 tive authentication to the bsdauth device.
109 If the publickey method is listed more than once, sshd(8) veri‐
111 fies that keys that have been used successfully are not reused
112 for subsequent authentications. For example,
113 "publickey,publickey" requires successful authentication using
114 two different public keys.
115 Note that each authentication method listed should also be ex‐
117 plicitly enabled in the configuration.
118 The available authentication methods are: "gssapi-with-mic",
120 "hostbased", "keyboard-interactive", "none" (used for access to
121 password-less accounts when PermitEmptyPasswords is enabled),
122 "password" and "publickey".
123 AuthorizedKeysCommand
125 Specifies a program to be used to look up the user's public keys.
126 The program must be owned by root, not writable by group or oth‐
127 ers and specified by an absolute path. Arguments to
128 AuthorizedKeysCommand accept the tokens described in the TOKENS
129 section. If no arguments are specified then the username of the
130 target user is used.
131 The program should produce on standard output zero or more lines
133 of authorized_keys output (see AUTHORIZED_KEYS in sshd(8)).
134 AuthorizedKeysCommand is tried after the usual AuthorizedKeysFile
135 files and will not be executed if a matching key is found there.
136 By default, no AuthorizedKeysCommand is run.
137 AuthorizedKeysCommandUser
139 Specifies the user under whose account the AuthorizedKeysCommand
140 is run. It is recommended to use a dedicated user that has no
141 other role on the host than running authorized keys commands. If
142 AuthorizedKeysCommand is specified but AuthorizedKeysCommandUser
143 is not, then sshd(8) will refuse to start.
144 AuthorizedKeysFile
146 Specifies the file that contains the public keys used for user
147 authentication. The format is described in the AUTHORIZED_KEYS
148 FILE FORMAT section of sshd(8). Arguments to AuthorizedKeysFile
149 accept the tokens described in the TOKENS section. After expan‐
150 sion, AuthorizedKeysFile is taken to be an absolute path or one
151 relative to the user's home directory. Multiple files may be
152 listed, separated by whitespace. Alternately this option may be
153 set to none to skip checking for user keys in files. The default
154 is ".ssh/authorized_keys .ssh/authorized_keys2".
155 AuthorizedPrincipalsCommand
157 Specifies a program to be used to generate the list of allowed
158 certificate principals as per AuthorizedPrincipalsFile. The pro‐
159 gram must be owned by root, not writable by group or others and
160 specified by an absolute path. Arguments to
161 AuthorizedPrincipalsCommand accept the tokens described in the
162 TOKENS section. If no arguments are specified then the username
163 of the target user is used.
164 The program should produce on standard output zero or more lines
166 of AuthorizedPrincipalsFile output. If either
167 AuthorizedPrincipalsCommand or AuthorizedPrincipalsFile is speci‐
168 fied, then certificates offered by the client for authentication
169 must contain a principal that is listed. By default, no
170 AuthorizedPrincipalsCommand is run.
171 AuthorizedPrincipalsCommandUser
173 Specifies the user under whose account the
174 AuthorizedPrincipalsCommand is run. It is recommended to use a
175 dedicated user that has no other role on the host than running
176 authorized principals commands. If AuthorizedPrincipalsCommand
177 is specified but AuthorizedPrincipalsCommandUser is not, then
178 sshd(8) will refuse to start.
179 AuthorizedPrincipalsFile
181 Specifies a file that lists principal names that are accepted for
182 certificate authentication. When using certificates signed by a
183 key listed in TrustedUserCAKeys, this file lists names, one of
184 which must appear in the certificate for it to be accepted for
185 authentication. Names are listed one per line preceded by key
186 options (as described in AUTHORIZED_KEYS FILE FORMAT in sshd(8)).
187 Empty lines and comments starting with ‘#’ are ignored.
188 Arguments to AuthorizedPrincipalsFile accept the tokens described
190 in the TOKENS section. After expansion, AuthorizedPrincipalsFile
191 is taken to be an absolute path or one relative to the user's
192 home directory. The default is none, i.e. not to use a princi‐
193 pals file – in this case, the username of the user must appear in
194 a certificate's principals list for it to be accepted.
195 Note that AuthorizedPrincipalsFile is only used when authentica‐
197 tion proceeds using a CA listed in TrustedUserCAKeys and is not
198 consulted for certification authorities trusted via
199 ~/.ssh/authorized_keys, though the principals= key option offers
200 a similar facility (see sshd(8) for details).
201 Banner The contents of the specified file are sent to the remote user
203 before authentication is allowed. If the argument is none then
204 no banner is displayed. By default, no banner is displayed.
205 CASignatureAlgorithms
207 The default is handled system-wide by crypto-policies(7). Infor‐
208 mation about defaults, how to modify the defaults and how to cus‐
209 tomize existing policies with sub-policies are present in manual
210 page update-crypto-policies(8).
211 Specifies which algorithms are allowed for signing of certifi‐
213 cates by certificate authorities (CAs). If the specified list
214 begins with a ‘+’ character, then the specified algorithms will
215 be appended to the default set instead of replacing them. If the
216 specified list begins with a ‘-’ character, then the specified
217 algorithms (including wildcards) will be removed from the default
218 set instead of replacing them.
219 Certificates signed using other algorithms will not be accepted
221 for public key or host-based authentication.
222 ChrootDirectory
224 Specifies the pathname of a directory to chroot(2) to after au‐
225 thentication. At session startup sshd(8) checks that all compo‐
226 nents of the pathname are root-owned directories which are not
227 writable by any other user or group. After the chroot, sshd(8)
228 changes the working directory to the user's home directory. Ar‐
229 guments to ChrootDirectory accept the tokens described in the
230 TOKENS section.
231 The ChrootDirectory must contain the necessary files and directo‐
233 ries to support the user's session. For an interactive session
234 this requires at least a shell, typically sh(1), and basic /dev
235 nodes such as null(4), zero(4), stdin(4), stdout(4), stderr(4),
236 and tty(4) devices. For file transfer sessions using SFTP no ad‐
237 ditional configuration of the environment is necessary if the in-
238 process sftp-server is used, though sessions which use logging
239 may require /dev/log inside the chroot directory on some operat‐
240 ing systems (see sftp-server(8) for details).
241 For safety, it is very important that the directory hierarchy be
243 prevented from modification by other processes on the system (es‐
244 pecially those outside the jail). Misconfiguration can lead to
245 unsafe environments which sshd(8) cannot detect.
246 The default is none, indicating not to chroot(2).
248 Ciphers
250 The default is handled system-wide by crypto-policies(7). Infor‐
251 mation about defaults, how to modify the defaults and how to cus‐
252 tomize existing policies with sub-policies are present in manual
253 page update-crypto-policies(8).
254 Specifies the ciphers allowed. Multiple ciphers must be comma-
256 separated. If the specified list begins with a ‘+’ character,
257 then the specified ciphers will be appended to the built-in
258 openssh default set instead of replacing them. If the specified
259 list begins with a ‘-’ character, then the specified ciphers (in‐
260 cluding wildcards) will be removed from the built-in openssh de‐
261 fault set instead of replacing them. If the specified list be‐
262 gins with a ‘^’ character, then the specified ciphers will be
263 placed at the head of the built-in openssh default set.
264 The supported ciphers are:
266 3des-cbc
268 aes128-cbc
269 aes192-cbc
270 aes256-cbc
271 aes128-ctr
272 aes192-ctr
273 aes256-ctr
274 aes128-gcm@openssh.com
275 aes256-gcm@openssh.com
276 chacha20-poly1305@openssh.com
277 The list of available ciphers may also be obtained using "ssh -Q
279 cipher".
280 ClientAliveCountMax
282 Sets the number of client alive messages which may be sent with‐
283 out sshd(8) receiving any messages back from the client. If this
284 threshold is reached while client alive messages are being sent,
285 sshd will disconnect the client, terminating the session. It is
286 important to note that the use of client alive messages is very
287 different from TCPKeepAlive. The client alive messages are sent
288 through the encrypted channel and therefore will not be spoofa‐
289 ble. The TCP keepalive option enabled by TCPKeepAlive is spoofa‐
290 ble. The client alive mechanism is valuable when the client or
291 server depend on knowing when a connection has become unrespon‐
292 sive.
293 The default value is 3. If ClientAliveInterval is set to 15, and
295 ClientAliveCountMax is left at the default, unresponsive SSH
296 clients will be disconnected after approximately 45 seconds.
297 Setting a zero ClientAliveCountMax disables connection termina‐
298 tion.
299 ClientAliveInterval
301 Sets a timeout interval in seconds after which if no data has
302 been received from the client, sshd(8) will send a message
303 through the encrypted channel to request a response from the
304 client. The default is 0, indicating that these messages will
305 not be sent to the client.
306 Compression
308 Specifies whether compression is enabled after the user has au‐
309 thenticated successfully. The argument must be yes, delayed (a
310 legacy synonym for yes) or no. The default is yes.
311 DenyGroups
313 This keyword can be followed by a list of group name patterns,
314 separated by spaces. Login is disallowed for users whose primary
315 group or supplementary group list matches one of the patterns.
316 Only group names are valid; a numerical group ID is not recog‐
317 nized. By default, login is allowed for all groups. The al‐
318 low/deny groups directives are processed in the following order:
319 DenyGroups, AllowGroups.
320 See PATTERNS in ssh_config(5) for more information on patterns.
322 DenyUsers
324 This keyword can be followed by a list of user name patterns,
325 separated by spaces. Login is disallowed for user names that
326 match one of the patterns. Only user names are valid; a numeri‐
327 cal user ID is not recognized. By default, login is allowed for
328 all users. If the pattern takes the form USER@HOST then USER and
329 HOST are separately checked, restricting logins to particular
330 users from particular hosts. HOST criteria may additionally con‐
331 tain addresses to match in CIDR address/masklen format. The al‐
332 low/deny users directives are processed in the following order:
333 DenyUsers, AllowUsers.
334 See PATTERNS in ssh_config(5) for more information on patterns.
336 DisableForwarding
338 Disables all forwarding features, including X11, ssh-agent(1),
339 TCP and StreamLocal. This option overrides all other forwarding-
340 related options and may simplify restricted configurations.
341 ExposeAuthInfo
343 Writes a temporary file containing a list of authentication meth‐
344 ods and public credentials (e.g. keys) used to authenticate the
345 user. The location of the file is exposed to the user session
346 through the SSH_USER_AUTH environment variable. The default is
347 no.
348 FingerprintHash
350 Specifies the hash algorithm used when logging key fingerprints.
351 Valid options are: md5 and sha256. The default is sha256.
352 ForceCommand
354 Forces the execution of the command specified by ForceCommand,
355 ignoring any command supplied by the client and ~/.ssh/rc if
356 present. The command is invoked by using the user's login shell
357 with the -c option. This applies to shell, command, or subsystem
358 execution. It is most useful inside a Match block. The command
359 originally supplied by the client is available in the
360 SSH_ORIGINAL_COMMAND environment variable. Specifying a command
361 of internal-sftp will force the use of an in-process SFTP server
362 that requires no support files when used with ChrootDirectory.
363 The default is none.
364 GatewayPorts
366 Specifies whether remote hosts are allowed to connect to ports
367 forwarded for the client. By default, sshd(8) binds remote port
368 forwardings to the loopback address. This prevents other remote
369 hosts from connecting to forwarded ports. GatewayPorts can be
370 used to specify that sshd should allow remote port forwardings to
371 bind to non-loopback addresses, thus allowing other hosts to con‐
372 nect. The argument may be no to force remote port forwardings to
373 be available to the local host only, yes to force remote port
374 forwardings to bind to the wildcard address, or clientspecified
375 to allow the client to select the address to which the forwarding
376 is bound. The default is no.
377 GSSAPIAuthentication
379 Specifies whether user authentication based on GSSAPI is allowed.
380 The default is no.
381 GSSAPICleanupCredentials
383 Specifies whether to automatically destroy the user's credentials
384 cache on logout. The default is yes.
385 GSSAPIEnablek5users
387 Specifies whether to look at .k5users file for GSSAPI authentica‐
388 tion access control. Further details are described in ksu(1).
389 The default is no.
390 GSSAPIKeyExchange
392 Specifies whether key exchange based on GSSAPI is allowed. GSSAPI
393 key exchange doesn't rely on ssh keys to verify host identity.
394 The default is no.
395 GSSAPIStrictAcceptorCheck
397 Determines whether to be strict about the identity of the GSSAPI
398 acceptor a client authenticates against. If set to yes then the
399 client must authenticate against the host service on the current
400 hostname. If set to no then the client may authenticate against
401 any service key stored in the machine's default store. This fa‐
402 cility is provided to assist with operation on multi homed ma‐
403 chines. The default is yes.
404 GSSAPIStoreCredentialsOnRekey
406 Controls whether the user's GSSAPI credentials should be updated
407 following a successful connection rekeying. This option can be
408 used to accepted renewed or updated credentials from a compatible
409 client. The default is “no”.
410 For this to work GSSAPIKeyExchange needs to be enabled in the
412 server and also used by the client.
413 GSSAPIKexAlgorithms
415 The default is handled system-wide by crypto-policies(7). Infor‐
416 mation about defaults, how to modify the defaults and how to cus‐
417 tomize existing policies with sub-policies are present in manual
418 page update-crypto-policies(8).
419 The list of key exchange algorithms that are accepted by GSSAPI
421 key exchange. Possible values are
422 gss-gex-sha1-
424 gss-group1-sha1-
425 gss-group14-sha1-
426 gss-group14-sha256-
427 gss-group16-sha512-
428 gss-nistp256-sha256-
429 gss-curve25519-sha256-
430 This option only applies to connections using GSSAPI.
431 HostbasedAcceptedAlgorithms
433 Specifies the signature algorithms that will be accepted for
434 hostbased authentication as a list of comma-separated patterns.
435 Alternately if the specified list begins with a ‘+’ character,
436 then the specified signature algorithms will be appended to the
437 default set instead of replacing them. If the specified list be‐
438 gins with a ‘-’ character, then the specified signature algo‐
439 rithms (including wildcards) will be removed from the default set
440 instead of replacing them. If the specified list begins with a
441 ‘^’ character, then the specified signature algorithms will be
442 placed at the head of the default set. The default for this op‐
443 tion is:
444 ssh-ed25519-cert-v01@openssh.com,
446 ecdsa-sha2-nistp256-cert-v01@openssh.com,
447 ecdsa-sha2-nistp384-cert-v01@openssh.com,
448 ecdsa-sha2-nistp521-cert-v01@openssh.com,
449 sk-ssh-ed25519-cert-v01@openssh.com,
450 sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
451 rsa-sha2-512-cert-v01@openssh.com,
452 rsa-sha2-256-cert-v01@openssh.com,
453 ssh-rsa-cert-v01@openssh.com,
454 ssh-ed25519,
455 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
456 sk-ssh-ed25519@openssh.com,
457 sk-ecdsa-sha2-nistp256@openssh.com,
458 rsa-sha2-512,rsa-sha2-256,ssh-rsa
459 The list of available signature algorithms may also be obtained
461 using "ssh -Q HostbasedAcceptedAlgorithms". This was formerly
462 named HostbasedAcceptedKeyTypes.
463 HostbasedAuthentication
465 Specifies whether rhosts or /etc/hosts.equiv authentication to‐
466 gether with successful public key client host authentication is
467 allowed (host-based authentication). The default is no.
468 HostbasedUsesNameFromPacketOnly
470 Specifies whether or not the server will attempt to perform a re‐
471 verse name lookup when matching the name in the ~/.shosts,
472 ~/.rhosts, and /etc/hosts.equiv files during
473 HostbasedAuthentication. A setting of yes means that sshd(8)
474 uses the name supplied by the client rather than attempting to
475 resolve the name from the TCP connection itself. The default is
476 no.
477 HostCertificate
479 Specifies a file containing a public host certificate. The cer‐
480 tificate's public key must match a private host key already spec‐
481 ified by HostKey. The default behaviour of sshd(8) is not to
482 load any certificates.
483 HostKey
485 Specifies a file containing a private host key used by SSH. The
486 defaults are /etc/ssh/ssh_host_ecdsa_key,
487 /etc/ssh/ssh_host_ed25519_key and /etc/ssh/ssh_host_rsa_key.
488 Note that sshd(8) will refuse to use a file if it is group/world-
490 accessible and that the HostKeyAlgorithms option restricts which
491 of the keys are actually used by sshd(8).
492 It is possible to have multiple host key files. It is also pos‐
494 sible to specify public host key files instead. In this case op‐
495 erations on the private key will be delegated to an ssh-agent(1).
496 HostKeyAgent
498 Identifies the UNIX-domain socket used to communicate with an
499 agent that has access to the private host keys. If the string
500 "SSH_AUTH_SOCK" is specified, the location of the socket will be
501 read from the SSH_AUTH_SOCK environment variable.
502 HostKeyAlgorithms
504 The default is handled system-wide by crypto-policies(7). Infor‐
505 mation about defaults, how to modify the defaults and how to cus‐
506 tomize existing policies with sub-policies are present in manual
507 page update-crypto-policies(8).
508 Specifies the host key signature algorithms that the server of‐
510 fers. The list of available signature algorithms may also be ob‐
511 tained using "ssh -Q HostKeyAlgorithms".
512 IgnoreRhosts
514 Specifies whether to ignore per-user .rhosts and .shosts files
515 during HostbasedAuthentication. The system-wide /etc/hosts.equiv
516 and /etc/ssh/shosts.equiv are still used regardless of this set‐
517 ting.
518 Accepted values are yes (the default) to ignore all per-user
520 files, shosts-only to allow the use of .shosts but to ignore
521 .rhosts or no to allow both .shosts and rhosts.
522 IgnoreUserKnownHosts
524 Specifies whether sshd(8) should ignore the user's
525 ~/.ssh/known_hosts during HostbasedAuthentication and use only
526 the system-wide known hosts file /etc/ssh/known_hosts. The de‐
527 fault is “no”.
528 Include
530 Include the specified configuration file(s). Multiple pathnames
531 may be specified and each pathname may contain glob(7) wildcards
532 that will be expanded and processed in lexical order. Files
533 without absolute paths are assumed to be in /etc/ssh. An Include
534 directive may appear inside a Match block to perform conditional
535 inclusion.
536 IPQoS Specifies the IPv4 type-of-service or DSCP class for the connec‐
538 tion. Accepted values are af11, af12, af13, af21, af22, af23,
539 af31, af32, af33, af41, af42, af43, cs0, cs1, cs2, cs3, cs4, cs5,
540 cs6, cs7, ef, le, lowdelay, throughput, reliability, a numeric
541 value, or none to use the operating system default. This option
542 may take one or two arguments, separated by whitespace. If one
543 argument is specified, it is used as the packet class uncondi‐
544 tionally. If two values are specified, the first is automati‐
545 cally selected for interactive sessions and the second for non-
546 interactive sessions. The default is af21 (Low-Latency Data) for
547 interactive sessions and cs1 (Lower Effort) for non-interactive
548 sessions.
549 KbdInteractiveAuthentication
551 Specifies whether to allow keyboard-interactive authentication.
552 All authentication styles from login.conf(5) are supported. The
553 default is yes. The argument to this keyword must be yes or no.
554 ChallengeResponseAuthentication is a deprecated alias for this.
555 KerberosAuthentication
557 Specifies whether the password provided by the user for
558 PasswordAuthentication will be validated through the Kerberos
559 KDC. To use this option, the server needs a Kerberos servtab
560 which allows the verification of the KDC's identity. The default
561 is no.
562 KerberosGetAFSToken
564 If AFS is active and the user has a Kerberos 5 TGT, attempt to
565 acquire an AFS token before accessing the user's home directory.
566 The default is no.
567 KerberosOrLocalPasswd
569 If password authentication through Kerberos fails then the pass‐
570 word will be validated via any additional local mechanism such as
571 /etc/passwd. The default is yes.
572 KerberosTicketCleanup
574 Specifies whether to automatically destroy the user's ticket
575 cache file on logout. The default is yes.
576 KerberosUniqueCCache
578 Specifies whether to store the acquired tickets in the per-ses‐
579 sion credential cache under /tmp/ or whether to use per-user cre‐
580 dential cache as configured in /etc/krb5.conf. The default value
581 no can lead to overwriting previous tickets by subseqent connec‐
582 tions to the same user account.
583 KerberosUseKuserok
585 Specifies whether to look at .k5login file for user's aliases.
586 The default is yes.
587 KexAlgorithms
589 The default is handled system-wide by crypto-policies(7). Infor‐
590 mation about defaults, how to modify the defaults and how to cus‐
591 tomize existing policies with sub-policies are present in manual
592 page update-crypto-policies(8).
593 Specifies the available KEX (Key Exchange) algorithms. Multiple
595 algorithms must be comma-separated. Alternately if the specified
596 list begins with a ‘+’ character, then the specified methods will
597 be appended to the built-in openssh default set instead of re‐
598 placing them. If the specified list begins with a ‘-’ character,
599 then the specified algorithms (including wildcards) will be re‐
600 moved from the built-in openssh default set instead of replacing
601 them. If the specified list begins with a ‘^’ character, then
602 the specified algorithms will be placed at the head of the built-
603 in openssh default set. The supported algorithms are:
604 curve25519-sha256
606 curve25519-sha256@libssh.org
607 diffie-hellman-group1-sha1
608 diffie-hellman-group14-sha1
609 diffie-hellman-group14-sha256
610 diffie-hellman-group16-sha512
611 diffie-hellman-group18-sha512
612 diffie-hellman-group-exchange-sha1
613 diffie-hellman-group-exchange-sha256
614 ecdh-sha2-nistp256
615 ecdh-sha2-nistp384
616 ecdh-sha2-nistp521
617 sntrup761x25519-sha512@openssh.com
618 The list of available key exchange algorithms may also be ob‐
620 tained using "ssh -Q KexAlgorithms".
621 ListenAddress
623 Specifies the local addresses sshd(8) should listen on. The fol‐
624 lowing forms may be used:
625 ListenAddress hostname|address [rdomain domain]
627 ListenAddress hostname:port [rdomain domain]
628 ListenAddress IPv4_address:port [rdomain domain]
629 ListenAddress [hostname|address]:port [rdomain domain]
630 The optional rdomain qualifier requests sshd(8) listen in an ex‐
632 plicit routing domain. If port is not specified, sshd will lis‐
633 ten on the address and all Port options specified. The default
634 is to listen on all local addresses on the current default rout‐
635 ing domain. Multiple ListenAddress options are permitted. For
636 more information on routing domains, see rdomain(4).
637 LoginGraceTime
639 The server disconnects after this time if the user has not suc‐
640 cessfully logged in. If the value is 0, there is no time limit.
641 The default is 120 seconds.
642 LogLevel
644 Gives the verbosity level that is used when logging messages from
645 sshd(8). The possible values are: QUIET, FATAL, ERROR, INFO,
646 VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO.
647 DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify
648 higher levels of debugging output. Logging with a DEBUG level
649 violates the privacy of users and is not recommended.
650 LogVerbose
652 Specify one or more overrides to LogLevel. An override consists
653 of a pattern lists that matches the source file, function and
654 line number to force detailed logging for. For example, an over‐
655 ride pattern of:
656 kex.c:*:1000,*:kex_exchange_identification():*,packet.c:*
658 would enable detailed logging for line 1000 of kex.c, everything
660 in the kex_exchange_identification() function, and all code in
661 the packet.c file. This option is intended for debugging and no
662 overrides are enabled by default.
663 MACs The default is handled system-wide by crypto-policies(7). Infor‐
665 mation about defaults, how to modify the defaults and how to cus‐
666 tomize existing policies with sub-policies are present in manual
667 page update-crypto-policies(8).
668 Specifies the available MAC (message authentication code) algo‐
670 rithms. The MAC algorithm is used for data integrity protection.
671 Multiple algorithms must be comma-separated. If the specified
672 list begins with a ‘+’ character, then the specified algorithms
673 will be appended to the built-in openssh default set instead of
674 replacing them. If the specified list begins with a ‘-’ charac‐
675 ter, then the specified algorithms (including wildcards) will be
676 removed from the built-in openssh default set instead of replac‐
677 ing them. If the specified list begins with a ‘^’ character,
678 then the specified algorithms will be placed at the head of the
679 built-in openssh default set.
680 The algorithms that contain "-etm" calculate the MAC after en‐
682 cryption (encrypt-then-mac). These are considered safer and
683 their use recommended. The supported MACs are:
684 hmac-md5
686 hmac-md5-96
687 hmac-sha1
688 hmac-sha1-96
689 hmac-sha2-256
690 hmac-sha2-512
691 umac-64@openssh.com
692 umac-128@openssh.com
693 hmac-md5-etm@openssh.com
694 hmac-md5-96-etm@openssh.com
695 hmac-sha1-etm@openssh.com
696 hmac-sha1-96-etm@openssh.com
697 hmac-sha2-256-etm@openssh.com
698 hmac-sha2-512-etm@openssh.com
699 umac-64-etm@openssh.com
700 umac-128-etm@openssh.com
701 The list of available MAC algorithms may also be obtained using
703 "ssh -Q mac".
704 Match Introduces a conditional block. If all of the criteria on the
706 Match line are satisfied, the keywords on the following lines
707 override those set in the global section of the config file, un‐
708 til either another Match line or the end of the file. If a key‐
709 word appears in multiple Match blocks that are satisfied, only
710 the first instance of the keyword is applied.
711 The arguments to Match are one or more criteria-pattern pairs or
713 the single token All which matches all criteria. The available
714 criteria are User, Group, Host, LocalAddress, LocalPort, RDomain,
715 and Address (with RDomain representing the rdomain(4) on which
716 the connection was received).
717 The match patterns may consist of single entries or comma-sepa‐
719 rated lists and may use the wildcard and negation operators de‐
720 scribed in the PATTERNS section of ssh_config(5).
721 The patterns in an Address criteria may additionally contain ad‐
723 dresses to match in CIDR address/masklen format, such as
724 192.0.2.0/24 or 2001:db8::/32. Note that the mask length pro‐
725 vided must be consistent with the address - it is an error to
726 specify a mask length that is too long for the address or one
727 with bits set in this host portion of the address. For example,
728 192.0.2.0/33 and 192.0.2.0/8, respectively.
729 Only a subset of keywords may be used on the lines following a
731 Match keyword. Available keywords are AcceptEnv,
732 AllowAgentForwarding, AllowGroups, AllowStreamLocalForwarding,
733 AllowTcpForwarding, AllowUsers, AuthenticationMethods,
734 AuthorizedKeysCommand, AuthorizedKeysCommandUser,
735 AuthorizedKeysFile, AuthorizedPrincipalsCommand,
736 AuthorizedPrincipalsCommandUser, AuthorizedPrincipalsFile,
737 Banner, ChrootDirectory, ClientAliveCountMax,
738 ClientAliveInterval, DenyGroups, DenyUsers, DisableForwarding,
739 ForceCommand, GatewayPorts, GSSAPIAuthentication,
740 HostbasedAcceptedAlgorithms, HostbasedAuthentication,
741 HostbasedUsesNameFromPacketOnly, IgnoreRhosts, Include, IPQoS,
742 KbdInteractiveAuthentication, KerberosAuthentication,
743 KerberosUseKuserok, LogLevel, MaxAuthTries, MaxSessions,
744 PasswordAuthentication, PermitEmptyPasswords, PermitListen,
745 PermitOpen, PermitRootLogin, PermitTTY, PermitTunnel,
746 PermitUserRC, PubkeyAcceptedAlgorithms, PubkeyAuthentication,
747 RekeyLimit, RevokedKeys, RDomain, SetEnv, StreamLocalBindMask,
748 StreamLocalBindUnlink, TrustedUserCAKeys, X11DisplayOffset,
749 X11MaxDisplays, X11Forwarding and X11UseLocalhost.
750 MaxAuthTries
752 Specifies the maximum number of authentication attempts permitted
753 per connection. Once the number of failures reaches half this
754 value, additional failures are logged. The default is 6.
755 MaxSessions
757 Specifies the maximum number of open shell, login or subsystem
758 (e.g. sftp) sessions permitted per network connection. Multiple
759 sessions may be established by clients that support connection
760 multiplexing. Setting MaxSessions to 1 will effectively disable
761 session multiplexing, whereas setting it to 0 will prevent all
762 shell, login and subsystem sessions while still permitting for‐
763 warding. The default is 10.
764 MaxStartups
766 Specifies the maximum number of concurrent unauthenticated con‐
767 nections to the SSH daemon. Additional connections will be
768 dropped until authentication succeeds or the LoginGraceTime ex‐
769 pires for a connection. The default is 10:30:100.
770 Alternatively, random early drop can be enabled by specifying the
772 three colon separated values start:rate:full (e.g. "10:30:60").
773 sshd(8) will refuse connection attempts with a probability of
774 rate/100 (30%) if there are currently start (10) unauthenticated
775 connections. The probability increases linearly and all connec‐
776 tion attempts are refused if the number of unauthenticated con‐
777 nections reaches full (60).
778 ModuliFile
780 Specifies the moduli(5) file that contains the Diffie-Hellman
781 groups used for the “diffie-hellman-group-exchange-sha1” and
782 “diffie-hellman-group-exchange-sha256” key exchange methods. The
783 default is /etc/ssh/moduli.
784 PasswordAuthentication
786 Specifies whether password authentication is allowed. The de‐
787 fault is yes.
788 PermitEmptyPasswords
790 When password authentication is allowed, it specifies whether the
791 server allows login to accounts with empty password strings. The
792 default is no.
793 PermitListen
795 Specifies the addresses/ports on which a remote TCP port forward‐
796 ing may listen. The listen specification must be one of the fol‐
797 lowing forms:
798 PermitListen port
800 PermitListen host:port
801 Multiple permissions may be specified by separating them with
803 whitespace. An argument of any can be used to remove all re‐
804 strictions and permit any listen requests. An argument of none
805 can be used to prohibit all listen requests. The host name may
806 contain wildcards as described in the PATTERNS section in
807 ssh_config(5). The wildcard ‘*’ can also be used in place of a
808 port number to allow all ports. By default all port forwarding
809 listen requests are permitted. Note that the GatewayPorts option
810 may further restrict which addresses may be listened on. Note
811 also that ssh(1) will request a listen host of “localhost” if no
812 listen host was specifically requested, and this name is treated
813 differently to explicit localhost addresses of “127.0.0.1” and
814 “::1”.
815 PermitOpen
817 Specifies the destinations to which TCP port forwarding is per‐
818 mitted. The forwarding specification must be one of the follow‐
819 ing forms:
820 PermitOpen host:port
822 PermitOpen IPv4_addr:port
823 PermitOpen [IPv6_addr]:port
824 Multiple forwards may be specified by separating them with white‐
826 space. An argument of any can be used to remove all restrictions
827 and permit any forwarding requests. An argument of none can be
828 used to prohibit all forwarding requests. The wildcard ‘*’ can
829 be used for host or port to allow all hosts or ports respec‐
830 tively. Otherwise, no pattern matching or address lookups are
831 performed on supplied names. By default all port forwarding re‐
832 quests are permitted.
833 PermitRootLogin
835 Specifies whether root can log in using ssh(1). The argument
836 must be yes, prohibit-password, forced-commands-only, or no. The
837 default is prohibit-password.
838 If this option is set to prohibit-password (or its deprecated
840 alias, without-password), password and keyboard-interactive au‐
841 thentication are disabled for root.
842 If this option is set to forced-commands-only, root login with
844 public key authentication will be allowed, but only if the
845 command option has been specified (which may be useful for taking
846 remote backups even if root login is normally not allowed). All
847 other authentication methods are disabled for root.
848 If this option is set to no, root is not allowed to log in.
850 PermitTTY
852 Specifies whether pty(4) allocation is permitted. The default is
853 yes.
854 PermitTunnel
856 Specifies whether tun(4) device forwarding is allowed. The argu‐
857 ment must be yes, point-to-point (layer 3), ethernet (layer 2),
858 or no. Specifying yes permits both point-to-point and ethernet.
859 The default is no.
860 Independent of this setting, the permissions of the selected
862 tun(4) device must allow access to the user.
863 PermitUserEnvironment
865 Specifies whether ~/.ssh/environment and environment= options in
866 ~/.ssh/authorized_keys are processed by sshd(8). Valid options
867 are yes, no or a pattern-list specifying which environment vari‐
868 able names to accept (for example "LANG,LC_*"). The default is
869 no. Enabling environment processing may enable users to bypass
870 access restrictions in some configurations using mechanisms such
871 as LD_PRELOAD.
872 PermitUserRC
874 Specifies whether any ~/.ssh/rc file is executed. The default is
875 yes.
876 PerSourceMaxStartups
878 Specifies the number of unauthenticated connections allowed from
879 a given source address, or “none” if there is no limit. This
880 limit is applied in addition to MaxStartups, whichever is lower.
881 The default is none.
882 PerSourceNetBlockSize
884 Specifies the number of bits of source address that are grouped
885 together for the purposes of applying PerSourceMaxStartups lim‐
886 its. Values for IPv4 and optionally IPv6 may be specified, sepa‐
887 rated by a colon. The default is 32:128, which means each ad‐
888 dress is considered individually.
889 PidFile
891 Specifies the file that contains the process ID of the SSH dae‐
892 mon, or none to not write one. The default is /var/run/sshd.pid.
893 Port Specifies the port number that sshd(8) listens on. The default
895 is 22. Multiple options of this type are permitted. See also
896 ListenAddress.
897 PrintLastLog
899 Specifies whether sshd(8) should print the date and time of the
900 last user login when a user logs in interactively. The default
901 is yes.
902 PrintMotd
904 Specifies whether sshd(8) should print /etc/motd when a user logs
905 in interactively. (On some systems it is also printed by the
906 shell, /etc/profile, or equivalent.) The default is yes.
907 PubkeyAcceptedAlgorithms
909 The default is handled system-wide by crypto-policies(7). Infor‐
910 mation about defaults, how to modify the defaults and how to cus‐
911 tomize existing policies with sub-policies are present in manual
912 page update-crypto-policies(8).
913 Specifies the signature algorithms that will be accepted for pub‐
915 lic key authentication as a list of comma-separated patterns.
916 Alternately if the specified list begins with a ‘+’ character,
917 then the specified algorithms will be appended to the built-in
918 openssh default set instead of replacing them. If the specified
919 list begins with a ‘-’ character, then the specified algorithms
920 (including wildcards) will be removed from the built-in openssh
921 default set instead of replacing them. If the specified list be‐
922 gins with a ‘^’ character, then the specified algorithms will be
923 placed at the head of the built-in openssh default set.
924 The list of available signature algorithms may also be obtained
926 using "ssh -Q PubkeyAcceptedAlgorithms".
927 PubkeyAuthOptions
929 Sets one or more public key authentication options. The sup‐
930 ported keywords are: none (the default; indicating no additional
931 options are enabled), touch-required and verify-required.
932 The touch-required option causes public key authentication using
934 a FIDO authenticator algorithm (i.e. ecdsa-sk or ed25519-sk) to
935 always require the signature to attest that a physically present
936 user explicitly confirmed the authentication (usually by touching
937 the authenticator). By default, sshd(8) requires user presence
938 unless overridden with an authorized_keys option. The
939 touch-required flag disables this override.
940 The verify-required option requires a FIDO key signature attest
942 that the user was verified, e.g. via a PIN.
943 Neither the touch-required or verify-required options have any
945 effect for other, non-FIDO, public key types.
946 PubkeyAuthentication
948 Specifies whether public key authentication is allowed. The de‐
949 fault is yes.
950 RekeyLimit
952 Specifies the maximum amount of data that may be transmitted be‐
953 fore the session key is renegotiated, optionally followed by a
954 maximum amount of time that may pass before the session key is
955 renegotiated. The first argument is specified in bytes and may
956 have a suffix of ‘K’, ‘M’, or ‘G’ to indicate Kilobytes,
957 Megabytes, or Gigabytes, respectively. The default is between
958 ‘1G’ and ‘4G’, depending on the cipher. The optional second
959 value is specified in seconds and may use any of the units docu‐
960 mented in the TIME FORMATS section. The default value for
961 RekeyLimit is default none, which means that rekeying is per‐
962 formed after the cipher's default amount of data has been sent or
963 received and no time based rekeying is done.
964 RequiredRSASize
966 Specifies the minimum RSA key size (in bits) that sshd(8) will
967 accept. User and host-based authentication keys smaller than
968 this limit will be refused. The default is 1024 bits. Note that
969 this limit may only be raised from the default.
970 RevokedKeys
972 Specifies revoked public keys file, or none to not use one. Keys
973 listed in this file will be refused for public key authentica‐
974 tion. Note that if this file is not readable, then public key
975 authentication will be refused for all users. Keys may be speci‐
976 fied as a text file, listing one public key per line, or as an
977 OpenSSH Key Revocation List (KRL) as generated by ssh-keygen(1).
978 For more information on KRLs, see the KEY REVOCATION LISTS sec‐
979 tion in ssh-keygen(1).
980 RDomain
982 Specifies an explicit routing domain that is applied after au‐
983 thentication has completed. The user session, as well as any
984 forwarded or listening IP sockets, will be bound to this
985 rdomain(4). If the routing domain is set to %D, then the domain
986 in which the incoming connection was received will be applied.
987 SecurityKeyProvider
989 Specifies a path to a library that will be used when loading FIDO
990 authenticator-hosted keys, overriding the default of using the
991 built-in USB HID support.
992 SetEnv Specifies one or more environment variables to set in child ses‐
994 sions started by sshd(8) as “NAME=VALUE”. The environment value
995 may be quoted (e.g. if it contains whitespace characters). Envi‐
996 ronment variables set by SetEnv override the default environment
997 and any variables specified by the user via AcceptEnv or
998 PermitUserEnvironment.
999 StreamLocalBindMask
1001 Sets the octal file creation mode mask (umask) used when creating
1002 a Unix-domain socket file for local or remote port forwarding.
1003 This option is only used for port forwarding to a Unix-domain
1004 socket file.
1005 The default value is 0177, which creates a Unix-domain socket
1007 file that is readable and writable only by the owner. Note that
1008 not all operating systems honor the file mode on Unix-domain
1009 socket files.
1010 StreamLocalBindUnlink
1012 Specifies whether to remove an existing Unix-domain socket file
1013 for local or remote port forwarding before creating a new one.
1014 If the socket file already exists and StreamLocalBindUnlink is
1015 not enabled, sshd will be unable to forward the port to the Unix-
1016 domain socket file. This option is only used for port forwarding
1017 to a Unix-domain socket file.
1018 The argument must be yes or no. The default is no.
1020 StrictModes
1022 Specifies whether sshd(8) should check file modes and ownership
1023 of the user's files and home directory before accepting login.
1024 This is normally desirable because novices sometimes accidentally
1025 leave their directory or files world-writable. The default is
1026 yes. Note that this does not apply to ChrootDirectory, whose
1027 permissions and ownership are checked unconditionally.
1028 Subsystem
1030 Configures an external subsystem (e.g. file transfer daemon).
1031 Arguments should be a subsystem name and a command (with optional
1032 arguments) to execute upon subsystem request.
1033 The command sftp-server implements the SFTP file transfer subsys‐
1035 tem.
1036 Alternately the name internal-sftp implements an in-process SFTP
1038 server. This may simplify configurations using ChrootDirectory
1039 to force a different filesystem root on clients.
1040 By default no subsystems are defined.
1042 SyslogFacility
1044 Gives the facility code that is used when logging messages from
1045 sshd(8). The possible values are: DAEMON, USER, AUTH, AUTHPRIV,
1046 LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1047 The default is AUTH.
1048 TCPKeepAlive
1050 Specifies whether the system should send TCP keepalive messages
1051 to the other side. If they are sent, death of the connection or
1052 crash of one of the machines will be properly noticed. However,
1053 this means that connections will die if the route is down tempo‐
1054 rarily, and some people find it annoying. On the other hand, if
1055 TCP keepalives are not sent, sessions may hang indefinitely on
1056 the server, leaving "ghost" users and consuming server resources.
1057 The default is yes (to send TCP keepalive messages), and the
1059 server will notice if the network goes down or the client host
1060 crashes. This avoids infinitely hanging sessions.
1061 To disable TCP keepalive messages, the value should be set to no.
1063 TrustedUserCAKeys
1065 Specifies a file containing public keys of certificate authori‐
1066 ties that are trusted to sign user certificates for authentica‐
1067 tion, or none to not use one. Keys are listed one per line;
1068 empty lines and comments starting with ‘#’ are allowed. If a
1069 certificate is presented for authentication and has its signing
1070 CA key listed in this file, then it may be used for authentica‐
1071 tion for any user listed in the certificate's principals list.
1072 Note that certificates that lack a list of principals will not be
1073 permitted for authentication using TrustedUserCAKeys. For more
1074 details on certificates, see the CERTIFICATES section in
1075 ssh-keygen(1).
1076 UseDNS Specifies whether sshd(8) should look up the remote host name,
1078 and to check that the resolved host name for the remote IP ad‐
1079 dress maps back to the very same IP address.
1080 If this option is set to no (the default) then only addresses and
1082 not host names may be used in ~/.ssh/authorized_keys from and
1083 sshd_config Match Host directives.
1084 UsePAM Enables the Pluggable Authentication Module interface. If set to
1086 yes this will enable PAM authentication using
1087 KbdInteractiveAuthentication and PasswordAuthentication in addi‐
1088 tion to PAM account and session module processing for all authen‐
1089 tication types.
1090 Because PAM keyboard-interactive authentication usually serves an
1092 equivalent role to password authentication, you should disable
1093 either PasswordAuthentication or KbdInteractiveAuthentication.
1094 If UsePAM is enabled, you will not be able to run sshd(8) as a
1096 non-root user. The default is no.
1097 VersionAddendum
1099 Optionally specifies additional text to append to the SSH proto‐
1100 col banner sent by the server upon connection. The default is
1101 none.
1102 X11DisplayOffset
1104 Specifies the first display number available for sshd(8)'s X11
1105 forwarding. This prevents sshd from interfering with real X11
1106 servers. The default is 10.
1107 X11MaxDisplays
1109 Specifies the maximum number of displays available for sshd(8)'s
1110 X11 forwarding. This prevents sshd from exhausting local ports.
1111 The default is 1000.
1112 X11Forwarding
1114 Specifies whether X11 forwarding is permitted. The argument must
1115 be yes or no. The default is no.
1116 When X11 forwarding is enabled, there may be additional exposure
1118 to the server and to client displays if the sshd(8) proxy display
1119 is configured to listen on the wildcard address (see
1120 X11UseLocalhost), though this is not the default. Additionally,
1121 the authentication spoofing and authentication data verification
1122 and substitution occur on the client side. The security risk of
1123 using X11 forwarding is that the client's X11 display server may
1124 be exposed to attack when the SSH client requests forwarding (see
1125 the warnings for ForwardX11 in ssh_config(5)). A system adminis‐
1126 trator may have a stance in which they want to protect clients
1127 that may expose themselves to attack by unwittingly requesting
1128 X11 forwarding, which can warrant a no setting.
1129 Note that disabling X11 forwarding does not prevent users from
1131 forwarding X11 traffic, as users can always install their own
1132 forwarders.
1133 X11UseLocalhost
1135 Specifies whether sshd(8) should bind the X11 forwarding server
1136 to the loopback address or to the wildcard address. By default,
1137 sshd binds the forwarding server to the loopback address and sets
1138 the hostname part of the DISPLAY environment variable to
1139 localhost. This prevents remote hosts from connecting to the
1140 proxy display. However, some older X11 clients may not function
1141 with this configuration. X11UseLocalhost may be set to no to
1142 specify that the forwarding server should be bound to the wild‐
1143 card address. The argument must be yes or no. The default is
1144 yes.
1145 XAuthLocation
1147 Specifies the full pathname of the xauth(1) program, or none to
1148 not use one. The default is /usr/bin/xauth.
1149
1151 sshd(8) command-line arguments and configuration file options that spec‐
1152 ify time may be expressed using a sequence of the form: time[qualifier],
1153 where time is a positive integer value and qualifier is one of the fol‐
1154 lowing:
1155 ⟨none⟩ seconds
1157 s | S seconds
1158 m | M minutes
1159 h | H hours
1160 d | D days
1161 w | W weeks
1162 Each member of the sequence is added together to calculate the total time
1164 value.
1165 Time format examples:
1167 600 600 seconds (10 minutes)
1169 10m 10 minutes
1170 1h30m 1 hour 30 minutes (90 minutes)
1171
1173 Arguments to some keywords can make use of tokens, which are expanded at
1174 runtime:
1175 %% A literal ‘%’.
1177 %D The routing domain in which the incoming connection was re‐
1178 ceived.
1179 %F The fingerprint of the CA key.
1180 %f The fingerprint of the key or certificate.
1181 %h The home directory of the user.
1182 %i The key ID in the certificate.
1183 %K The base64-encoded CA key.
1184 %k The base64-encoded key or certificate for authentication.
1185 %s The serial number of the certificate.
1186 %T The type of the CA key.
1187 %t The key or certificate type.
1188 %U The numeric user ID of the target user.
1189 %u The username.
1190 AuthorizedKeysCommand accepts the tokens %%, %f, %h, %k, %t, %U, and %u.
1192 AuthorizedKeysFile accepts the tokens %%, %h, %U, and %u.
1194 AuthorizedPrincipalsCommand accepts the tokens %%, %F, %f, %h, %i, %K,
1196 %k, %s, %T, %t, %U, and %u.
1197 AuthorizedPrincipalsFile accepts the tokens %%, %h, %U, and %u.
1199 ChrootDirectory accepts the tokens %%, %h, %U, and %u.
1201 RoutingDomain accepts the token %D.
1203
1205 /etc/ssh/sshd_config
1206 Contains configuration data for sshd(8). This file should be
1207 writable by root only, but it is recommended (though not neces‐
1208 sary) that it be world-readable.
1209
1211 sftp-server(8), sshd(8)
1212
1214 OpenSSH is a derivative of the original and free ssh 1.2.12 release by
1215 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
1216 de Raadt and Dug Song removed many bugs, re-added newer features and cre‐
1217 ated OpenSSH. Markus Friedl contributed the support for SSH protocol
1218 versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support
1219 for privilege separation.
1220BSD September 3, 2021 BSD