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). To see
208 the defaults and how to modify this default, see manual page
209 update-crypto-policies(8).
210 Specifies which algorithms are allowed for signing of certifi‐
212 cates by certificate authorities (CAs). If the specified list
213 begins with a ‘+’ character, then the specified algorithms will
214 be appended to the default set instead of replacing them. If the
215 specified list begins with a ‘-’ character, then the specified
216 algorithms (including wildcards) will be removed from the default
217 set instead of replacing them.
218 Certificates signed using other algorithms will not be accepted
220 for public key or host-based authentication.
221 ChrootDirectory
223 Specifies the pathname of a directory to chroot(2) to after au‐
224 thentication. At session startup sshd(8) checks that all compo‐
225 nents of the pathname are root-owned directories which are not
226 writable by any other user or group. After the chroot, sshd(8)
227 changes the working directory to the user's home directory. Ar‐
228 guments to ChrootDirectory accept the tokens described in the
229 TOKENS section.
230 The ChrootDirectory must contain the necessary files and directo‐
232 ries to support the user's session. For an interactive session
233 this requires at least a shell, typically sh(1), and basic /dev
234 nodes such as null(4), zero(4), stdin(4), stdout(4), stderr(4),
235 and tty(4) devices. For file transfer sessions using SFTP no ad‐
236 ditional configuration of the environment is necessary if the in-
237 process sftp-server is used, though sessions which use logging
238 may require /dev/log inside the chroot directory on some operat‐
239 ing systems (see sftp-server(8) for details).
240 For safety, it is very important that the directory hierarchy be
242 prevented from modification by other processes on the system (es‐
243 pecially those outside the jail). Misconfiguration can lead to
244 unsafe environments which sshd(8) cannot detect.
245 The default is none, indicating not to chroot(2).
247 Ciphers
249 The default is handled system-wide by crypto-policies(7). To see
250 the defaults and how to modify this default, see manual page
251 update-crypto-policies(8).
252 Specifies the ciphers allowed. Multiple ciphers must be comma-
254 separated. If the specified list begins with a ‘+’ character,
255 then the specified ciphers will be appended to the built-in
256 openssh default set instead of replacing them. If the specified
257 list begins with a ‘-’ character, then the specified ciphers (in‐
258 cluding wildcards) will be removed from the built-in openssh de‐
259 fault set instead of replacing them. If the specified list be‐
260 gins with a ‘^’ character, then the specified ciphers will be
261 placed at the head of the built-in openssh default set.
262 The supported ciphers are:
264 3des-cbc
266 aes128-cbc
267 aes192-cbc
268 aes256-cbc
269 aes128-ctr
270 aes192-ctr
271 aes256-ctr
272 aes128-gcm@openssh.com
273 aes256-gcm@openssh.com
274 chacha20-poly1305@openssh.com
275 The list of available ciphers may also be obtained using "ssh -Q
277 cipher".
278 ClientAliveCountMax
280 Sets the number of client alive messages which may be sent with‐
281 out sshd(8) receiving any messages back from the client. If this
282 threshold is reached while client alive messages are being sent,
283 sshd will disconnect the client, terminating the session. It is
284 important to note that the use of client alive messages is very
285 different from TCPKeepAlive. The client alive messages are sent
286 through the encrypted channel and therefore will not be spoofa‐
287 ble. The TCP keepalive option enabled by TCPKeepAlive is spoofa‐
288 ble. The client alive mechanism is valuable when the client or
289 server depend on knowing when a connection has become unrespon‐
290 sive.
291 The default value is 3. If ClientAliveInterval is set to 15, and
293 ClientAliveCountMax is left at the default, unresponsive SSH
294 clients will be disconnected after approximately 45 seconds.
295 Setting a zero ClientAliveCountMax disables connection termina‐
296 tion.
297 ClientAliveInterval
299 Sets a timeout interval in seconds after which if no data has
300 been received from the client, sshd(8) will send a message
301 through the encrypted channel to request a response from the
302 client. The default is 0, indicating that these messages will
303 not be sent to the client.
304 Compression
306 Specifies whether compression is enabled after the user has au‐
307 thenticated successfully. The argument must be yes, delayed (a
308 legacy synonym for yes) or no. The default is yes.
309 DenyGroups
311 This keyword can be followed by a list of group name patterns,
312 separated by spaces. Login is disallowed for users whose primary
313 group or supplementary group list matches one of the patterns.
314 Only group names are valid; a numerical group ID is not recog‐
315 nized. By default, login is allowed for all groups. The al‐
316 low/deny groups directives are processed in the following order:
317 DenyGroups, AllowGroups.
318 See PATTERNS in ssh_config(5) for more information on patterns.
320 DenyUsers
322 This keyword can be followed by a list of user name patterns,
323 separated by spaces. Login is disallowed for user names that
324 match one of the patterns. Only user names are valid; a numeri‐
325 cal user ID is not recognized. By default, login is allowed for
326 all users. If the pattern takes the form USER@HOST then USER and
327 HOST are separately checked, restricting logins to particular
328 users from particular hosts. HOST criteria may additionally con‐
329 tain addresses to match in CIDR address/masklen format. The al‐
330 low/deny users directives are processed in the following order:
331 DenyUsers, AllowUsers.
332 See PATTERNS in ssh_config(5) for more information on patterns.
334 DisableForwarding
336 Disables all forwarding features, including X11, ssh-agent(1),
337 TCP and StreamLocal. This option overrides all other forwarding-
338 related options and may simplify restricted configurations.
339 ExposeAuthInfo
341 Writes a temporary file containing a list of authentication meth‐
342 ods and public credentials (e.g. keys) used to authenticate the
343 user. The location of the file is exposed to the user session
344 through the SSH_USER_AUTH environment variable. The default is
345 no.
346 FingerprintHash
348 Specifies the hash algorithm used when logging key fingerprints.
349 Valid options are: md5 and sha256. The default is sha256.
350 ForceCommand
352 Forces the execution of the command specified by ForceCommand,
353 ignoring any command supplied by the client and ~/.ssh/rc if
354 present. The command is invoked by using the user's login shell
355 with the -c option. This applies to shell, command, or subsystem
356 execution. It is most useful inside a Match block. The command
357 originally supplied by the client is available in the
358 SSH_ORIGINAL_COMMAND environment variable. Specifying a command
359 of internal-sftp will force the use of an in-process SFTP server
360 that requires no support files when used with ChrootDirectory.
361 The default is none.
362 GatewayPorts
364 Specifies whether remote hosts are allowed to connect to ports
365 forwarded for the client. By default, sshd(8) binds remote port
366 forwardings to the loopback address. This prevents other remote
367 hosts from connecting to forwarded ports. GatewayPorts can be
368 used to specify that sshd should allow remote port forwardings to
369 bind to non-loopback addresses, thus allowing other hosts to con‐
370 nect. The argument may be no to force remote port forwardings to
371 be available to the local host only, yes to force remote port
372 forwardings to bind to the wildcard address, or clientspecified
373 to allow the client to select the address to which the forwarding
374 is bound. The default is no.
375 GSSAPIAuthentication
377 Specifies whether user authentication based on GSSAPI is allowed.
378 The default is no.
379 GSSAPICleanupCredentials
381 Specifies whether to automatically destroy the user's credentials
382 cache on logout. The default is yes.
383 GSSAPIEnablek5users
385 Specifies whether to look at .k5users file for GSSAPI authentica‐
386 tion access control. Further details are described in ksu(1).
387 The default is no.
388 GSSAPIKeyExchange
390 Specifies whether key exchange based on GSSAPI is allowed. GSSAPI
391 key exchange doesn't rely on ssh keys to verify host identity.
392 The default is no.
393 GSSAPIStrictAcceptorCheck
395 Determines whether to be strict about the identity of the GSSAPI
396 acceptor a client authenticates against. If set to yes then the
397 client must authenticate against the host service on the current
398 hostname. If set to no then the client may authenticate against
399 any service key stored in the machine's default store. This fa‐
400 cility is provided to assist with operation on multi homed ma‐
401 chines. The default is yes.
402 GSSAPIStoreCredentialsOnRekey
404 Controls whether the user's GSSAPI credentials should be updated
405 following a successful connection rekeying. This option can be
406 used to accepted renewed or updated credentials from a compatible
407 client. The default is “no”.
408 For this to work GSSAPIKeyExchange needs to be enabled in the
410 server and also used by the client.
411 GSSAPIKexAlgorithms
413 The default is handled system-wide by crypto-policies(7). To see
414 the defaults and how to modify this default, see manual page
415 update-crypto-policies(8).
416 The list of key exchange algorithms that are accepted by GSSAPI
418 key exchange. Possible values are
419 gss-gex-sha1-
421 gss-group1-sha1-
422 gss-group14-sha1-
423 gss-group14-sha256-
424 gss-group16-sha512-
425 gss-nistp256-sha256-
426 gss-curve25519-sha256-
427 This option only applies to connections using GSSAPI.
428 HostbasedAcceptedAlgorithms
430 Specifies the signature algorithms that will be accepted for
431 hostbased authentication as a list of comma-separated patterns.
432 Alternately if the specified list begins with a ‘+’ character,
433 then the specified signature algorithms will be appended to the
434 default set instead of replacing them. If the specified list be‐
435 gins with a ‘-’ character, then the specified signature algo‐
436 rithms (including wildcards) will be removed from the default set
437 instead of replacing them. If the specified list begins with a
438 ‘^’ character, then the specified signature algorithms will be
439 placed at the head of the default set. The default for this op‐
440 tion is:
441 ssh-ed25519-cert-v01@openssh.com,
443 ecdsa-sha2-nistp256-cert-v01@openssh.com,
444 ecdsa-sha2-nistp384-cert-v01@openssh.com,
445 ecdsa-sha2-nistp521-cert-v01@openssh.com,
446 sk-ssh-ed25519-cert-v01@openssh.com,
447 sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
448 rsa-sha2-512-cert-v01@openssh.com,
449 rsa-sha2-256-cert-v01@openssh.com,
450 ssh-rsa-cert-v01@openssh.com,
451 ssh-ed25519,
452 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
453 sk-ssh-ed25519@openssh.com,
454 sk-ecdsa-sha2-nistp256@openssh.com,
455 rsa-sha2-512,rsa-sha2-256,ssh-rsa
456 The list of available signature algorithms may also be obtained
458 using "ssh -Q HostbasedAcceptedAlgorithms". This was formerly
459 named HostbasedAcceptedKeyTypes.
460 HostbasedAuthentication
462 Specifies whether rhosts or /etc/hosts.equiv authentication to‐
463 gether with successful public key client host authentication is
464 allowed (host-based authentication). The default is no.
465 HostbasedUsesNameFromPacketOnly
467 Specifies whether or not the server will attempt to perform a re‐
468 verse name lookup when matching the name in the ~/.shosts,
469 ~/.rhosts, and /etc/hosts.equiv files during
470 HostbasedAuthentication. A setting of yes means that sshd(8)
471 uses the name supplied by the client rather than attempting to
472 resolve the name from the TCP connection itself. The default is
473 no.
474 HostCertificate
476 Specifies a file containing a public host certificate. The cer‐
477 tificate's public key must match a private host key already spec‐
478 ified by HostKey. The default behaviour of sshd(8) is not to
479 load any certificates.
480 HostKey
482 Specifies a file containing a private host key used by SSH. The
483 defaults are /etc/ssh/ssh_host_ecdsa_key,
484 /etc/ssh/ssh_host_ed25519_key and /etc/ssh/ssh_host_rsa_key.
485 Note that sshd(8) will refuse to use a file if it is group/world-
487 accessible and that the HostKeyAlgorithms option restricts which
488 of the keys are actually used by sshd(8).
489 It is possible to have multiple host key files. It is also pos‐
491 sible to specify public host key files instead. In this case op‐
492 erations on the private key will be delegated to an ssh-agent(1).
493 HostKeyAgent
495 Identifies the UNIX-domain socket used to communicate with an
496 agent that has access to the private host keys. If the string
497 "SSH_AUTH_SOCK" is specified, the location of the socket will be
498 read from the SSH_AUTH_SOCK environment variable.
499 HostKeyAlgorithms
501 The default is handled system-wide by crypto-policies(7). To see
502 the defaults and how to modify this default, see manual page
503 update-crypto-policies(8).
504 Specifies the host key signature algorithms that the server of‐
506 fers. The list of available signature algorithms may also be ob‐
507 tained using "ssh -Q HostKeyAlgorithms".
508 IgnoreRhosts
510 Specifies whether to ignore per-user .rhosts and .shosts files
511 during HostbasedAuthentication. The system-wide /etc/hosts.equiv
512 and /etc/ssh/shosts.equiv are still used regardless of this set‐
513 ting.
514 Accepted values are yes (the default) to ignore all per-user
516 files, shosts-only to allow the use of .shosts but to ignore
517 .rhosts or no to allow both .shosts and rhosts.
518 IgnoreUserKnownHosts
520 Specifies whether sshd(8) should ignore the user's
521 ~/.ssh/known_hosts during HostbasedAuthentication and use only
522 the system-wide known hosts file /etc/ssh/known_hosts. The de‐
523 fault is “no”.
524 Include
526 Include the specified configuration file(s). Multiple pathnames
527 may be specified and each pathname may contain glob(7) wildcards
528 that will be expanded and processed in lexical order. Files
529 without absolute paths are assumed to be in /etc/ssh. An Include
530 directive may appear inside a Match block to perform conditional
531 inclusion.
532 IPQoS Specifies the IPv4 type-of-service or DSCP class for the connec‐
534 tion. Accepted values are af11, af12, af13, af21, af22, af23,
535 af31, af32, af33, af41, af42, af43, cs0, cs1, cs2, cs3, cs4, cs5,
536 cs6, cs7, ef, le, lowdelay, throughput, reliability, a numeric
537 value, or none to use the operating system default. This option
538 may take one or two arguments, separated by whitespace. If one
539 argument is specified, it is used as the packet class uncondi‐
540 tionally. If two values are specified, the first is automati‐
541 cally selected for interactive sessions and the second for non-
542 interactive sessions. The default is af21 (Low-Latency Data) for
543 interactive sessions and cs1 (Lower Effort) for non-interactive
544 sessions.
545 KbdInteractiveAuthentication
547 Specifies whether to allow keyboard-interactive authentication.
548 All authentication styles from login.conf(5) are supported. The
549 default is yes. The argument to this keyword must be yes or no.
550 ChallengeResponseAuthentication is a deprecated alias for this.
551 KerberosAuthentication
553 Specifies whether the password provided by the user for
554 PasswordAuthentication will be validated through the Kerberos
555 KDC. To use this option, the server needs a Kerberos servtab
556 which allows the verification of the KDC's identity. The default
557 is no.
558 KerberosGetAFSToken
560 If AFS is active and the user has a Kerberos 5 TGT, attempt to
561 acquire an AFS token before accessing the user's home directory.
562 The default is no.
563 KerberosOrLocalPasswd
565 If password authentication through Kerberos fails then the pass‐
566 word will be validated via any additional local mechanism such as
567 /etc/passwd. The default is yes.
568 KerberosTicketCleanup
570 Specifies whether to automatically destroy the user's ticket
571 cache file on logout. The default is yes.
572 KerberosUniqueCCache
574 Specifies whether to store the acquired tickets in the per-ses‐
575 sion credential cache under /tmp/ or whether to use per-user cre‐
576 dential cache as configured in /etc/krb5.conf. The default value
577 no can lead to overwriting previous tickets by subseqent connec‐
578 tions to the same user account.
579 KerberosUseKuserok
581 Specifies whether to look at .k5login file for user's aliases.
582 The default is yes.
583 KexAlgorithms
585 The default is handled system-wide by crypto-policies(7). To see
586 the defaults and how to modify this default, see manual page
587 update-crypto-policies(8).
588 Specifies the available KEX (Key Exchange) algorithms. Multiple
590 algorithms must be comma-separated. Alternately if the specified
591 list begins with a ‘+’ character, then the specified algorithms
592 will be appended to the built-in openssh default set instead of
593 replacing them. If the specified list begins with a ‘-’ charac‐
594 ter, then the specified algorithms (including wildcards) will be
595 removed from the built-in openssh default set instead of replac‐
596 ing them. If the specified list begins with a ‘^’ character,
597 then the specified algorithms will be placed at the head of the
598 built-in openssh default set. The supported algorithms are:
599 curve25519-sha256
601 curve25519-sha256@libssh.org
602 diffie-hellman-group1-sha1
603 diffie-hellman-group14-sha1
604 diffie-hellman-group14-sha256
605 diffie-hellman-group16-sha512
606 diffie-hellman-group18-sha512
607 diffie-hellman-group-exchange-sha1
608 diffie-hellman-group-exchange-sha256
609 ecdh-sha2-nistp256
610 ecdh-sha2-nistp384
611 ecdh-sha2-nistp521
612 sntrup761x25519-sha512@openssh.com
613 The list of available key exchange algorithms may also be ob‐
615 tained using "ssh -Q KexAlgorithms".
616 ListenAddress
618 Specifies the local addresses sshd(8) should listen on. The fol‐
619 lowing forms may be used:
620 ListenAddress hostname|address [rdomain domain]
622 ListenAddress hostname:port [rdomain domain]
623 ListenAddress IPv4_address:port [rdomain domain]
624 ListenAddress [hostname|address]:port [rdomain domain]
625 The optional rdomain qualifier requests sshd(8) listen in an ex‐
627 plicit routing domain. If port is not specified, sshd will lis‐
628 ten on the address and all Port options specified. The default
629 is to listen on all local addresses on the current default rout‐
630 ing domain. Multiple ListenAddress options are permitted. For
631 more information on routing domains, see rdomain(4).
632 LoginGraceTime
634 The server disconnects after this time if the user has not suc‐
635 cessfully logged in. If the value is 0, there is no time limit.
636 The default is 120 seconds.
637 LogLevel
639 Gives the verbosity level that is used when logging messages from
640 sshd(8). The possible values are: QUIET, FATAL, ERROR, INFO,
641 VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO.
642 DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify
643 higher levels of debugging output. Logging with a DEBUG level
644 violates the privacy of users and is not recommended.
645 LogVerbose
647 Specify one or more overrides to LogLevel. An override consists
648 of a pattern lists that matches the source file, function and
649 line number to force detailed logging for. For example, an over‐
650 ride pattern of:
651 kex.c:*:1000,*:kex_exchange_identification():*,packet.c:*
653 would enable detailed logging for line 1000 of kex.c, everything
655 in the kex_exchange_identification() function, and all code in
656 the packet.c file. This option is intended for debugging and no
657 overrides are enabled by default.
658 MACs The default is handled system-wide by crypto-policies(7). To see
660 the defaults and how to modify this default, see manual page
661 update-crypto-policies(8).
662 Specifies the available MAC (message authentication code) algo‐
664 rithms. The MAC algorithm is used for data integrity protection.
665 Multiple algorithms must be comma-separated. If the specified
666 list begins with a ‘+’ character, then the specified algorithms
667 will be appended to the built-in openssh default set instead of
668 replacing them. If the specified list begins with a ‘-’ charac‐
669 ter, then the specified algorithms (including wildcards) will be
670 removed from the built-in openssh default set instead of replac‐
671 ing them. If the specified list begins with a ‘^’ character,
672 then the specified algorithms will be placed at the head of the
673 built-in openssh default set.
674 The algorithms that contain "-etm" calculate the MAC after en‐
676 cryption (encrypt-then-mac). These are considered safer and
677 their use recommended. The supported MACs are:
678 hmac-md5
680 hmac-md5-96
681 hmac-sha1
682 hmac-sha1-96
683 hmac-sha2-256
684 hmac-sha2-512
685 umac-64@openssh.com
686 umac-128@openssh.com
687 hmac-md5-etm@openssh.com
688 hmac-md5-96-etm@openssh.com
689 hmac-sha1-etm@openssh.com
690 hmac-sha1-96-etm@openssh.com
691 hmac-sha2-256-etm@openssh.com
692 hmac-sha2-512-etm@openssh.com
693 umac-64-etm@openssh.com
694 umac-128-etm@openssh.com
695 The list of available MAC algorithms may also be obtained using
697 "ssh -Q mac".
698 Match Introduces a conditional block. If all of the criteria on the
700 Match line are satisfied, the keywords on the following lines
701 override those set in the global section of the config file, un‐
702 til either another Match line or the end of the file. If a key‐
703 word appears in multiple Match blocks that are satisfied, only
704 the first instance of the keyword is applied.
705 The arguments to Match are one or more criteria-pattern pairs or
707 the single token All which matches all criteria. The available
708 criteria are User, Group, Host, LocalAddress, LocalPort, RDomain,
709 and Address (with RDomain representing the rdomain(4) on which
710 the connection was received).
711 The match patterns may consist of single entries or comma-sepa‐
713 rated lists and may use the wildcard and negation operators de‐
714 scribed in the PATTERNS section of ssh_config(5).
715 The patterns in an Address criteria may additionally contain ad‐
717 dresses to match in CIDR address/masklen format, such as
718 192.0.2.0/24 or 2001:db8::/32. Note that the mask length pro‐
719 vided must be consistent with the address - it is an error to
720 specify a mask length that is too long for the address or one
721 with bits set in this host portion of the address. For example,
722 192.0.2.0/33 and 192.0.2.0/8, respectively.
723 Only a subset of keywords may be used on the lines following a
725 Match keyword. Available keywords are AcceptEnv,
726 AllowAgentForwarding, AllowGroups, AllowStreamLocalForwarding,
727 AllowTcpForwarding, AllowUsers, AuthenticationMethods,
728 AuthorizedKeysCommand, AuthorizedKeysCommandUser,
729 AuthorizedKeysFile, AuthorizedPrincipalsCommand,
730 AuthorizedPrincipalsCommandUser, AuthorizedPrincipalsFile,
731 Banner, ChrootDirectory, ClientAliveCountMax,
732 ClientAliveInterval, DenyGroups, DenyUsers, DisableForwarding,
733 ForceCommand, GatewayPorts, GSSAPIAuthentication,
734 HostbasedAcceptedAlgorithms, HostbasedAuthentication,
735 HostbasedUsesNameFromPacketOnly, IgnoreRhosts, Include, IPQoS,
736 KbdInteractiveAuthentication, KerberosAuthentication,
737 KerberosUseKuserok, LogLevel, MaxAuthTries, MaxSessions,
738 PasswordAuthentication, PermitEmptyPasswords, PermitListen,
739 PermitOpen, PermitRootLogin, PermitTTY, PermitTunnel,
740 PermitUserRC, PubkeyAcceptedAlgorithms, PubkeyAuthentication,
741 RekeyLimit, RevokedKeys, RDomain, SetEnv, StreamLocalBindMask,
742 StreamLocalBindUnlink, TrustedUserCAKeys, X11DisplayOffset,
743 X11MaxDisplays, X11Forwarding and X11UseLocalhost.
744 MaxAuthTries
746 Specifies the maximum number of authentication attempts permitted
747 per connection. Once the number of failures reaches half this
748 value, additional failures are logged. The default is 6.
749 MaxSessions
751 Specifies the maximum number of open shell, login or subsystem
752 (e.g. sftp) sessions permitted per network connection. Multiple
753 sessions may be established by clients that support connection
754 multiplexing. Setting MaxSessions to 1 will effectively disable
755 session multiplexing, whereas setting it to 0 will prevent all
756 shell, login and subsystem sessions while still permitting for‐
757 warding. The default is 10.
758 MaxStartups
760 Specifies the maximum number of concurrent unauthenticated con‐
761 nections to the SSH daemon. Additional connections will be
762 dropped until authentication succeeds or the LoginGraceTime ex‐
763 pires for a connection. The default is 10:30:100.
764 Alternatively, random early drop can be enabled by specifying the
766 three colon separated values start:rate:full (e.g. "10:30:60").
767 sshd(8) will refuse connection attempts with a probability of
768 rate/100 (30%) if there are currently start (10) unauthenticated
769 connections. The probability increases linearly and all connec‐
770 tion attempts are refused if the number of unauthenticated con‐
771 nections reaches full (60).
772 ModuliFile
774 Specifies the moduli(5) file that contains the Diffie-Hellman
775 groups used for the “diffie-hellman-group-exchange-sha1” and
776 “diffie-hellman-group-exchange-sha256” key exchange methods. The
777 default is /etc/ssh/moduli.
778 PasswordAuthentication
780 Specifies whether password authentication is allowed. The de‐
781 fault is yes.
782 PermitEmptyPasswords
784 When password authentication is allowed, it specifies whether the
785 server allows login to accounts with empty password strings. The
786 default is no.
787 PermitListen
789 Specifies the addresses/ports on which a remote TCP port forward‐
790 ing may listen. The listen specification must be one of the fol‐
791 lowing forms:
792 PermitListen port
794 PermitListen host:port
795 Multiple permissions may be specified by separating them with
797 whitespace. An argument of any can be used to remove all re‐
798 strictions and permit any listen requests. An argument of none
799 can be used to prohibit all listen requests. The host name may
800 contain wildcards as described in the PATTERNS section in
801 ssh_config(5). The wildcard ‘*’ can also be used in place of a
802 port number to allow all ports. By default all port forwarding
803 listen requests are permitted. Note that the GatewayPorts option
804 may further restrict which addresses may be listened on. Note
805 also that ssh(1) will request a listen host of “localhost” if no
806 listen host was specifically requested, and this name is treated
807 differently to explicit localhost addresses of “127.0.0.1” and
808 “::1”.
809 PermitOpen
811 Specifies the destinations to which TCP port forwarding is per‐
812 mitted. The forwarding specification must be one of the follow‐
813 ing forms:
814 PermitOpen host:port
816 PermitOpen IPv4_addr:port
817 PermitOpen [IPv6_addr]:port
818 Multiple forwards may be specified by separating them with white‐
820 space. An argument of any can be used to remove all restrictions
821 and permit any forwarding requests. An argument of none can be
822 used to prohibit all forwarding requests. The wildcard ‘*’ can
823 be used for host or port to allow all hosts or ports respec‐
824 tively. Otherwise, no pattern matching or address lookups are
825 performed on supplied names. By default all port forwarding re‐
826 quests are permitted.
827 PermitRootLogin
829 Specifies whether root can log in using ssh(1). The argument
830 must be yes, prohibit-password, forced-commands-only, or no. The
831 default is prohibit-password.
832 If this option is set to prohibit-password (or its deprecated
834 alias, without-password), password and keyboard-interactive au‐
835 thentication are disabled for root.
836 If this option is set to forced-commands-only, root login with
838 public key authentication will be allowed, but only if the
839 command option has been specified (which may be useful for taking
840 remote backups even if root login is normally not allowed). All
841 other authentication methods are disabled for root.
842 If this option is set to no, root is not allowed to log in.
844 PermitTTY
846 Specifies whether pty(4) allocation is permitted. The default is
847 yes.
848 PermitTunnel
850 Specifies whether tun(4) device forwarding is allowed. The argu‐
851 ment must be yes, point-to-point (layer 3), ethernet (layer 2),
852 or no. Specifying yes permits both point-to-point and ethernet.
853 The default is no.
854 Independent of this setting, the permissions of the selected
856 tun(4) device must allow access to the user.
857 PermitUserEnvironment
859 Specifies whether ~/.ssh/environment and environment= options in
860 ~/.ssh/authorized_keys are processed by sshd(8). Valid options
861 are yes, no or a pattern-list specifying which environment vari‐
862 able names to accept (for example "LANG,LC_*"). The default is
863 no. Enabling environment processing may enable users to bypass
864 access restrictions in some configurations using mechanisms such
865 as LD_PRELOAD.
866 PermitUserRC
868 Specifies whether any ~/.ssh/rc file is executed. The default is
869 yes.
870 PerSourceMaxStartups
872 Specifies the number of unauthenticated connections allowed from
873 a given source address, or “none” if there is no limit. This
874 limit is applied in addition to MaxStartups, whichever is lower.
875 The default is none.
876 PerSourceNetBlockSize
878 Specifies the number of bits of source address that are grouped
879 together for the purposes of applying PerSourceMaxStartups lim‐
880 its. Values for IPv4 and optionally IPv6 may be specified, sepa‐
881 rated by a colon. The default is 32:128, which means each ad‐
882 dress is considered individually.
883 PidFile
885 Specifies the file that contains the process ID of the SSH dae‐
886 mon, or none to not write one. The default is /var/run/sshd.pid.
887 Port Specifies the port number that sshd(8) listens on. The default
889 is 22. Multiple options of this type are permitted. See also
890 ListenAddress.
891 PrintLastLog
893 Specifies whether sshd(8) should print the date and time of the
894 last user login when a user logs in interactively. The default
895 is yes.
896 PrintMotd
898 Specifies whether sshd(8) should print /etc/motd when a user logs
899 in interactively. (On some systems it is also printed by the
900 shell, /etc/profile, or equivalent.) The default is yes.
901 PubkeyAcceptedAlgorithms
903 The default is handled system-wide by crypto-policies(7). To see
904 the defaults and how to modify this default, see manual page
905 update-crypto-policies(8).
906 Specifies the signature algorithms that will be accepted for pub‐
908 lic key authentication as a list of comma-separated patterns.
909 Alternately if the specified list begins with a ‘+’ character,
910 then the specified algorithms will be appended to the built-in
911 openssh default set instead of replacing them. If the specified
912 list begins with a ‘-’ character, then the specified algorithms
913 (including wildcards) will be removed from the built-in openssh
914 default set instead of replacing them. If the specified list be‐
915 gins with a ‘^’ character, then the specified algorithms will be
916 placed at the head of the built-in openssh default set.
917 The list of available signature algorithms may also be obtained
919 using "ssh -Q PubkeyAcceptedAlgorithms".
920 PubkeyAuthOptions
922 Sets one or more public key authentication options. The sup‐
923 ported keywords are: none (the default; indicating no additional
924 options are enabled), touch-required and verify-required.
925 The touch-required option causes public key authentication using
927 a FIDO authenticator algorithm (i.e. ecdsa-sk or ed25519-sk) to
928 always require the signature to attest that a physically present
929 user explicitly confirmed the authentication (usually by touching
930 the authenticator). By default, sshd(8) requires user presence
931 unless overridden with an authorized_keys option. The
932 touch-required flag disables this override.
933 The verify-required option requires a FIDO key signature attest
935 that the user was verified, e.g. via a PIN.
936 Neither the touch-required or verify-required options have any
938 effect for other, non-FIDO, public key types.
939 PubkeyAuthentication
941 Specifies whether public key authentication is allowed. The de‐
942 fault is yes.
943 RekeyLimit
945 Specifies the maximum amount of data that may be transmitted be‐
946 fore the session key is renegotiated, optionally followed by a
947 maximum amount of time that may pass before the session key is
948 renegotiated. The first argument is specified in bytes and may
949 have a suffix of ‘K’, ‘M’, or ‘G’ to indicate Kilobytes,
950 Megabytes, or Gigabytes, respectively. The default is between
951 ‘1G’ and ‘4G’, depending on the cipher. The optional second
952 value is specified in seconds and may use any of the units docu‐
953 mented in the TIME FORMATS section. The default value for
954 RekeyLimit is default none, which means that rekeying is per‐
955 formed after the cipher's default amount of data has been sent or
956 received and no time based rekeying is done.
957 RevokedKeys
959 Specifies revoked public keys file, or none to not use one. Keys
960 listed in this file will be refused for public key authentica‐
961 tion. Note that if this file is not readable, then public key
962 authentication will be refused for all users. Keys may be speci‐
963 fied as a text file, listing one public key per line, or as an
964 OpenSSH Key Revocation List (KRL) as generated by ssh-keygen(1).
965 For more information on KRLs, see the KEY REVOCATION LISTS sec‐
966 tion in ssh-keygen(1).
967 RDomain
969 Specifies an explicit routing domain that is applied after au‐
970 thentication has completed. The user session, as well as any
971 forwarded or listening IP sockets, will be bound to this
972 rdomain(4). If the routing domain is set to %D, then the domain
973 in which the incoming connection was received will be applied.
974 SecurityKeyProvider
976 Specifies a path to a library that will be used when loading FIDO
977 authenticator-hosted keys, overriding the default of using the
978 built-in USB HID support.
979 SetEnv Specifies one or more environment variables to set in child ses‐
981 sions started by sshd(8) as “NAME=VALUE”. The environment value
982 may be quoted (e.g. if it contains whitespace characters). Envi‐
983 ronment variables set by SetEnv override the default environment
984 and any variables specified by the user via AcceptEnv or
985 PermitUserEnvironment.
986 StreamLocalBindMask
988 Sets the octal file creation mode mask (umask) used when creating
989 a Unix-domain socket file for local or remote port forwarding.
990 This option is only used for port forwarding to a Unix-domain
991 socket file.
992 The default value is 0177, which creates a Unix-domain socket
994 file that is readable and writable only by the owner. Note that
995 not all operating systems honor the file mode on Unix-domain
996 socket files.
997 StreamLocalBindUnlink
999 Specifies whether to remove an existing Unix-domain socket file
1000 for local or remote port forwarding before creating a new one.
1001 If the socket file already exists and StreamLocalBindUnlink is
1002 not enabled, sshd will be unable to forward the port to the Unix-
1003 domain socket file. This option is only used for port forwarding
1004 to a Unix-domain socket file.
1005 The argument must be yes or no. The default is no.
1007 StrictModes
1009 Specifies whether sshd(8) should check file modes and ownership
1010 of the user's files and home directory before accepting login.
1011 This is normally desirable because novices sometimes accidentally
1012 leave their directory or files world-writable. The default is
1013 yes. Note that this does not apply to ChrootDirectory, whose
1014 permissions and ownership are checked unconditionally.
1015 Subsystem
1017 Configures an external subsystem (e.g. file transfer daemon).
1018 Arguments should be a subsystem name and a command (with optional
1019 arguments) to execute upon subsystem request.
1020 The command sftp-server implements the SFTP file transfer subsys‐
1022 tem.
1023 Alternately the name internal-sftp implements an in-process SFTP
1025 server. This may simplify configurations using ChrootDirectory
1026 to force a different filesystem root on clients.
1027 By default no subsystems are defined.
1029 SyslogFacility
1031 Gives the facility code that is used when logging messages from
1032 sshd(8). The possible values are: DAEMON, USER, AUTH, AUTHPRIV,
1033 LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
1034 The default is AUTH.
1035 TCPKeepAlive
1037 Specifies whether the system should send TCP keepalive messages
1038 to the other side. If they are sent, death of the connection or
1039 crash of one of the machines will be properly noticed. However,
1040 this means that connections will die if the route is down tempo‐
1041 rarily, and some people find it annoying. On the other hand, if
1042 TCP keepalives are not sent, sessions may hang indefinitely on
1043 the server, leaving "ghost" users and consuming server resources.
1044 The default is yes (to send TCP keepalive messages), and the
1046 server will notice if the network goes down or the client host
1047 crashes. This avoids infinitely hanging sessions.
1048 To disable TCP keepalive messages, the value should be set to no.
1050 TrustedUserCAKeys
1052 Specifies a file containing public keys of certificate authori‐
1053 ties that are trusted to sign user certificates for authentica‐
1054 tion, or none to not use one. Keys are listed one per line;
1055 empty lines and comments starting with ‘#’ are allowed. If a
1056 certificate is presented for authentication and has its signing
1057 CA key listed in this file, then it may be used for authentica‐
1058 tion for any user listed in the certificate's principals list.
1059 Note that certificates that lack a list of principals will not be
1060 permitted for authentication using TrustedUserCAKeys. For more
1061 details on certificates, see the CERTIFICATES section in
1062 ssh-keygen(1).
1063 UseDNS Specifies whether sshd(8) should look up the remote host name,
1065 and to check that the resolved host name for the remote IP ad‐
1066 dress maps back to the very same IP address.
1067 If this option is set to no (the default) then only addresses and
1069 not host names may be used in ~/.ssh/authorized_keys from and
1070 sshd_config Match Host directives.
1071 UsePAM Enables the Pluggable Authentication Module interface. If set to
1073 yes this will enable PAM authentication using
1074 KbdInteractiveAuthentication and PasswordAuthentication in addi‐
1075 tion to PAM account and session module processing for all authen‐
1076 tication types.
1077 Because PAM keyboard-interactive authentication usually serves an
1079 equivalent role to password authentication, you should disable
1080 either PasswordAuthentication or KbdInteractiveAuthentication.
1081 If UsePAM is enabled, you will not be able to run sshd(8) as a
1083 non-root user. The default is no.
1084 VersionAddendum
1086 Optionally specifies additional text to append to the SSH proto‐
1087 col banner sent by the server upon connection. The default is
1088 none.
1089 X11DisplayOffset
1091 Specifies the first display number available for sshd(8)'s X11
1092 forwarding. This prevents sshd from interfering with real X11
1093 servers. The default is 10.
1094 X11MaxDisplays
1096 Specifies the maximum number of displays available for sshd(8)'s
1097 X11 forwarding. This prevents sshd from exhausting local ports.
1098 The default is 1000.
1099 X11Forwarding
1101 Specifies whether X11 forwarding is permitted. The argument must
1102 be yes or no. The default is no.
1103 When X11 forwarding is enabled, there may be additional exposure
1105 to the server and to client displays if the sshd(8) proxy display
1106 is configured to listen on the wildcard address (see
1107 X11UseLocalhost), though this is not the default. Additionally,
1108 the authentication spoofing and authentication data verification
1109 and substitution occur on the client side. The security risk of
1110 using X11 forwarding is that the client's X11 display server may
1111 be exposed to attack when the SSH client requests forwarding (see
1112 the warnings for ForwardX11 in ssh_config(5)). A system adminis‐
1113 trator may have a stance in which they want to protect clients
1114 that may expose themselves to attack by unwittingly requesting
1115 X11 forwarding, which can warrant a no setting.
1116 Note that disabling X11 forwarding does not prevent users from
1118 forwarding X11 traffic, as users can always install their own
1119 forwarders.
1120 X11UseLocalhost
1122 Specifies whether sshd(8) should bind the X11 forwarding server
1123 to the loopback address or to the wildcard address. By default,
1124 sshd binds the forwarding server to the loopback address and sets
1125 the hostname part of the DISPLAY environment variable to
1126 localhost. This prevents remote hosts from connecting to the
1127 proxy display. However, some older X11 clients may not function
1128 with this configuration. X11UseLocalhost may be set to no to
1129 specify that the forwarding server should be bound to the wild‐
1130 card address. The argument must be yes or no. The default is
1131 yes.
1132 XAuthLocation
1134 Specifies the full pathname of the xauth(1) program, or none to
1135 not use one. The default is /usr/bin/xauth.
1136
1138 sshd(8) command-line arguments and configuration file options that spec‐
1139 ify time may be expressed using a sequence of the form: time[qualifier],
1140 where time is a positive integer value and qualifier is one of the fol‐
1141 lowing:
1142 ⟨none⟩ seconds
1144 s | S seconds
1145 m | M minutes
1146 h | H hours
1147 d | D days
1148 w | W weeks
1149 Each member of the sequence is added together to calculate the total time
1151 value.
1152 Time format examples:
1154 600 600 seconds (10 minutes)
1156 10m 10 minutes
1157 1h30m 1 hour 30 minutes (90 minutes)
1158
1160 Arguments to some keywords can make use of tokens, which are expanded at
1161 runtime:
1162 %% A literal ‘%’.
1164 %D The routing domain in which the incoming connection was re‐
1165 ceived.
1166 %F The fingerprint of the CA key.
1167 %f The fingerprint of the key or certificate.
1168 %h The home directory of the user.
1169 %i The key ID in the certificate.
1170 %K The base64-encoded CA key.
1171 %k The base64-encoded key or certificate for authentication.
1172 %s The serial number of the certificate.
1173 %T The type of the CA key.
1174 %t The key or certificate type.
1175 %U The numeric user ID of the target user.
1176 %u The username.
1177 AuthorizedKeysCommand accepts the tokens %%, %f, %h, %k, %t, %U, and %u.
1179 AuthorizedKeysFile accepts the tokens %%, %h, %U, and %u.
1181 AuthorizedPrincipalsCommand accepts the tokens %%, %F, %f, %h, %i, %K,
1183 %k, %s, %T, %t, %U, and %u.
1184 AuthorizedPrincipalsFile accepts the tokens %%, %h, %U, and %u.
1186 ChrootDirectory accepts the tokens %%, %h, %U, and %u.
1188 RoutingDomain accepts the token %D.
1190
1192 /etc/ssh/sshd_config
1193 Contains configuration data for sshd(8). This file should be
1194 writable by root only, but it is recommended (though not neces‐
1195 sary) that it be world-readable.
1196
1198 sftp-server(8), sshd(8)
1199
1201 OpenSSH is a derivative of the original and free ssh 1.2.12 release by
1202 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
1203 de Raadt and Dug Song removed many bugs, re-added newer features and cre‐
1204 ated OpenSSH. Markus Friedl contributed the support for SSH protocol
1205 versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support
1206 for privilege separation.
1207BSD September 3, 2021 BSD