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1 | SSH_CONFIG(5) File Formats Manual SSH_CONFIG(5) | ||
2 | |||
3 | NAME | ||
4 | ssh_config M-bM-^@M-^S OpenSSH SSH client configuration files | ||
5 | |||
6 | SYNOPSIS | ||
7 | ~/.ssh/config | ||
8 | /etc/ssh/ssh_config | ||
9 | |||
10 | DESCRIPTION | ||
11 | ssh(1) obtains configuration data from the following sources in the | ||
12 | following order: | ||
13 | |||
14 | 1. command-line options | ||
15 | 2. user's configuration file (~/.ssh/config) | ||
16 | 3. system-wide configuration file (/etc/ssh/ssh_config) | ||
17 | |||
18 | For each parameter, the first obtained value will be used. The | ||
19 | configuration files contain sections separated by Host specifications, | ||
20 | and that section is only applied for hosts that match one of the patterns | ||
21 | given in the specification. The matched host name is usually the one | ||
22 | given on the command line (see the CanonicalizeHostname option for | ||
23 | exceptions). | ||
24 | |||
25 | Since the first obtained value for each parameter is used, more host- | ||
26 | specific declarations should be given near the beginning of the file, and | ||
27 | general defaults at the end. | ||
28 | |||
29 | The file contains keyword-argument pairs, one per line. Lines starting | ||
30 | with M-bM-^@M-^X#M-bM-^@M-^Y and empty lines are interpreted as comments. Arguments may | ||
31 | optionally be enclosed in double quotes (") in order to represent | ||
32 | arguments containing spaces. Configuration options may be separated by | ||
33 | whitespace or optional whitespace and exactly one M-bM-^@M-^X=M-bM-^@M-^Y; the latter format | ||
34 | is useful to avoid the need to quote whitespace when specifying | ||
35 | configuration options using the ssh, scp, and sftp -o option. | ||
36 | |||
37 | The possible keywords and their meanings are as follows (note that | ||
38 | keywords are case-insensitive and arguments are case-sensitive): | ||
39 | |||
40 | Host Restricts the following declarations (up to the next Host or | ||
41 | Match keyword) to be only for those hosts that match one of the | ||
42 | patterns given after the keyword. If more than one pattern is | ||
43 | provided, they should be separated by whitespace. A single M-bM-^@M-^X*M-bM-^@M-^Y | ||
44 | as a pattern can be used to provide global defaults for all | ||
45 | hosts. The host is usually the hostname argument given on the | ||
46 | command line (see the CanonicalizeHostname keyword for | ||
47 | exceptions). | ||
48 | |||
49 | A pattern entry may be negated by prefixing it with an | ||
50 | exclamation mark (M-bM-^@M-^X!M-bM-^@M-^Y). If a negated entry is matched, then the | ||
51 | Host entry is ignored, regardless of whether any other patterns | ||
52 | on the line match. Negated matches are therefore useful to | ||
53 | provide exceptions for wildcard matches. | ||
54 | |||
55 | See PATTERNS for more information on patterns. | ||
56 | |||
57 | Match Restricts the following declarations (up to the next Host or | ||
58 | Match keyword) to be used only when the conditions following the | ||
59 | Match keyword are satisfied. Match conditions are specified | ||
60 | using one or more criteria or the single token all which always | ||
61 | matches. The available criteria keywords are: canonical, exec, | ||
62 | host, originalhost, user, and localuser. The all criteria must | ||
63 | appear alone or immediately after canonical. Other criteria may | ||
64 | be combined arbitrarily. All criteria but all and canonical | ||
65 | require an argument. Criteria may be negated by prepending an | ||
66 | exclamation mark (M-bM-^@M-^X!M-bM-^@M-^Y). | ||
67 | |||
68 | The canonical keyword matches only when the configuration file is | ||
69 | being re-parsed after hostname canonicalization (see the | ||
70 | CanonicalizeHostname option.) This may be useful to specify | ||
71 | conditions that work with canonical host names only. The exec | ||
72 | keyword executes the specified command under the user's shell. | ||
73 | If the command returns a zero exit status then the condition is | ||
74 | considered true. Commands containing whitespace characters must | ||
75 | be quoted. Arguments to exec accept the tokens described in the | ||
76 | TOKENS section. | ||
77 | |||
78 | The other keywords' criteria must be single entries or comma- | ||
79 | separated lists and may use the wildcard and negation operators | ||
80 | described in the PATTERNS section. The criteria for the host | ||
81 | keyword are matched against the target hostname, after any | ||
82 | substitution by the Hostname or CanonicalizeHostname options. | ||
83 | The originalhost keyword matches against the hostname as it was | ||
84 | specified on the command-line. The user keyword matches against | ||
85 | the target username on the remote host. The localuser keyword | ||
86 | matches against the name of the local user running ssh(1) (this | ||
87 | keyword may be useful in system-wide ssh_config files). | ||
88 | |||
89 | AddKeysToAgent | ||
90 | Specifies whether keys should be automatically added to a running | ||
91 | ssh-agent(1). If this option is set to yes and a key is loaded | ||
92 | from a file, the key and its passphrase are added to the agent | ||
93 | with the default lifetime, as if by ssh-add(1). If this option | ||
94 | is set to ask, ssh(1) will require confirmation using the | ||
95 | SSH_ASKPASS program before adding a key (see ssh-add(1) for | ||
96 | details). If this option is set to confirm, each use of the key | ||
97 | must be confirmed, as if the -c option was specified to | ||
98 | ssh-add(1). If this option is set to no, no keys are added to | ||
99 | the agent. The argument must be yes, confirm, ask, or no (the | ||
100 | default). | ||
101 | |||
102 | AddressFamily | ||
103 | Specifies which address family to use when connecting. Valid | ||
104 | arguments are any (the default), inet (use IPv4 only), or inet6 | ||
105 | (use IPv6 only). | ||
106 | |||
107 | BatchMode | ||
108 | If set to yes, passphrase/password querying will be disabled. | ||
109 | This option is useful in scripts and other batch jobs where no | ||
110 | user is present to supply the password. The argument must be yes | ||
111 | or no (the default). | ||
112 | |||
113 | BindAddress | ||
114 | Use the specified address on the local machine as the source | ||
115 | address of the connection. Only useful on systems with more than | ||
116 | one address. Note that this option does not work if | ||
117 | UsePrivilegedPort is set to yes. | ||
118 | |||
119 | CanonicalDomains | ||
120 | When CanonicalizeHostname is enabled, this option specifies the | ||
121 | list of domain suffixes in which to search for the specified | ||
122 | destination host. | ||
123 | |||
124 | CanonicalizeFallbackLocal | ||
125 | Specifies whether to fail with an error when hostname | ||
126 | canonicalization fails. The default, yes, will attempt to look | ||
127 | up the unqualified hostname using the system resolver's search | ||
128 | rules. A value of no will cause ssh(1) to fail instantly if | ||
129 | CanonicalizeHostname is enabled and the target hostname cannot be | ||
130 | found in any of the domains specified by CanonicalDomains. | ||
131 | |||
132 | CanonicalizeHostname | ||
133 | Controls whether explicit hostname canonicalization is performed. | ||
134 | The default, no, is not to perform any name rewriting and let the | ||
135 | system resolver handle all hostname lookups. If set to yes then, | ||
136 | for connections that do not use a ProxyCommand, ssh(1) will | ||
137 | attempt to canonicalize the hostname specified on the command | ||
138 | line using the CanonicalDomains suffixes and | ||
139 | CanonicalizePermittedCNAMEs rules. If CanonicalizeHostname is | ||
140 | set to always, then canonicalization is applied to proxied | ||
141 | connections too. | ||
142 | |||
143 | If this option is enabled, then the configuration files are | ||
144 | processed again using the new target name to pick up any new | ||
145 | configuration in matching Host and Match stanzas. | ||
146 | |||
147 | CanonicalizeMaxDots | ||
148 | Specifies the maximum number of dot characters in a hostname | ||
149 | before canonicalization is disabled. The default, 1, allows a | ||
150 | single dot (i.e. hostname.subdomain). | ||
151 | |||
152 | CanonicalizePermittedCNAMEs | ||
153 | Specifies rules to determine whether CNAMEs should be followed | ||
154 | when canonicalizing hostnames. The rules consist of one or more | ||
155 | arguments of source_domain_list:target_domain_list, where | ||
156 | source_domain_list is a pattern-list of domains that may follow | ||
157 | CNAMEs in canonicalization, and target_domain_list is a pattern- | ||
158 | list of domains that they may resolve to. | ||
159 | |||
160 | For example, "*.a.example.com:*.b.example.com,*.c.example.com" | ||
161 | will allow hostnames matching "*.a.example.com" to be | ||
162 | canonicalized to names in the "*.b.example.com" or | ||
163 | "*.c.example.com" domains. | ||
164 | |||
165 | CertificateFile | ||
166 | Specifies a file from which the user's certificate is read. A | ||
167 | corresponding private key must be provided separately in order to | ||
168 | use this certificate either from an IdentityFile directive or -i | ||
169 | flag to ssh(1), via ssh-agent(1), or via a PKCS11Provider. | ||
170 | |||
171 | Arguments to CertificateFile may use the tilde syntax to refer to | ||
172 | a user's home directory or the tokens described in the TOKENS | ||
173 | section. | ||
174 | |||
175 | It is possible to have multiple certificate files specified in | ||
176 | configuration files; these certificates will be tried in | ||
177 | sequence. Multiple CertificateFile directives will add to the | ||
178 | list of certificates used for authentication. | ||
179 | |||
180 | ChallengeResponseAuthentication | ||
181 | Specifies whether to use challenge-response authentication. The | ||
182 | argument to this keyword must be yes (the default) or no. | ||
183 | |||
184 | CheckHostIP | ||
185 | If set to yes (the default), ssh(1) will additionally check the | ||
186 | host IP address in the known_hosts file. This allows it to | ||
187 | detect if a host key changed due to DNS spoofing and will add | ||
188 | addresses of destination hosts to ~/.ssh/known_hosts in the | ||
189 | process, regardless of the setting of StrictHostKeyChecking. If | ||
190 | the option is set to no, the check will not be executed. | ||
191 | |||
192 | Cipher Specifies the cipher to use for encrypting the session in | ||
193 | protocol version 1. Currently, blowfish, 3des (the default), and | ||
194 | des are supported, though des is only supported in the ssh(1) | ||
195 | client for interoperability with legacy protocol 1 | ||
196 | implementations; its use is strongly discouraged due to | ||
197 | cryptographic weaknesses. | ||
198 | |||
199 | Ciphers | ||
200 | Specifies the ciphers allowed for protocol version 2 in order of | ||
201 | preference. Multiple ciphers must be comma-separated. If the | ||
202 | specified value begins with a M-bM-^@M-^X+M-bM-^@M-^Y character, then the specified | ||
203 | ciphers will be appended to the default set instead of replacing | ||
204 | them. If the specified value begins with a M-bM-^@M-^X-M-bM-^@M-^Y character, then | ||
205 | the specified ciphers (including wildcards) will be removed from | ||
206 | the default set instead of replacing them. | ||
207 | |||
208 | The supported ciphers are: | ||
209 | |||
210 | 3des-cbc | ||
211 | aes128-cbc | ||
212 | aes192-cbc | ||
213 | aes256-cbc | ||
214 | aes128-ctr | ||
215 | aes192-ctr | ||
216 | aes256-ctr | ||
217 | aes128-gcm@openssh.com | ||
218 | aes256-gcm@openssh.com | ||
219 | arcfour | ||
220 | arcfour128 | ||
221 | arcfour256 | ||
222 | blowfish-cbc | ||
223 | cast128-cbc | ||
224 | chacha20-poly1305@openssh.com | ||
225 | |||
226 | The default is: | ||
227 | |||
228 | chacha20-poly1305@openssh.com, | ||
229 | aes128-ctr,aes192-ctr,aes256-ctr, | ||
230 | aes128-gcm@openssh.com,aes256-gcm@openssh.com, | ||
231 | aes128-cbc,aes192-cbc,aes256-cbc | ||
232 | |||
233 | The list of available ciphers may also be obtained using "ssh -Q | ||
234 | cipher". | ||
235 | |||
236 | ClearAllForwardings | ||
237 | Specifies that all local, remote, and dynamic port forwardings | ||
238 | specified in the configuration files or on the command line be | ||
239 | cleared. This option is primarily useful when used from the | ||
240 | ssh(1) command line to clear port forwardings set in | ||
241 | configuration files, and is automatically set by scp(1) and | ||
242 | sftp(1). The argument must be yes or no (the default). | ||
243 | |||
244 | Compression | ||
245 | Specifies whether to use compression. The argument must be yes | ||
246 | or no (the default). | ||
247 | |||
248 | CompressionLevel | ||
249 | Specifies the compression level to use if compression is enabled. | ||
250 | The argument must be an integer from 1 (fast) to 9 (slow, best). | ||
251 | The default level is 6, which is good for most applications. The | ||
252 | meaning of the values is the same as in gzip(1). Note that this | ||
253 | option applies to protocol version 1 only. | ||
254 | |||
255 | ConnectionAttempts | ||
256 | Specifies the number of tries (one per second) to make before | ||
257 | exiting. The argument must be an integer. This may be useful in | ||
258 | scripts if the connection sometimes fails. The default is 1. | ||
259 | |||
260 | ConnectTimeout | ||
261 | Specifies the timeout (in seconds) used when connecting to the | ||
262 | SSH server, instead of using the default system TCP timeout. | ||
263 | This value is used only when the target is down or really | ||
264 | unreachable, not when it refuses the connection. | ||
265 | |||
266 | ControlMaster | ||
267 | Enables the sharing of multiple sessions over a single network | ||
268 | connection. When set to yes, ssh(1) will listen for connections | ||
269 | on a control socket specified using the ControlPath argument. | ||
270 | Additional sessions can connect to this socket using the same | ||
271 | ControlPath with ControlMaster set to no (the default). These | ||
272 | sessions will try to reuse the master instance's network | ||
273 | connection rather than initiating new ones, but will fall back to | ||
274 | connecting normally if the control socket does not exist, or is | ||
275 | not listening. | ||
276 | |||
277 | Setting this to ask will cause ssh(1) to listen for control | ||
278 | connections, but require confirmation using ssh-askpass(1). If | ||
279 | the ControlPath cannot be opened, ssh(1) will continue without | ||
280 | connecting to a master instance. | ||
281 | |||
282 | X11 and ssh-agent(1) forwarding is supported over these | ||
283 | multiplexed connections, however the display and agent forwarded | ||
284 | will be the one belonging to the master connection i.e. it is not | ||
285 | possible to forward multiple displays or agents. | ||
286 | |||
287 | Two additional options allow for opportunistic multiplexing: try | ||
288 | to use a master connection but fall back to creating a new one if | ||
289 | one does not already exist. These options are: auto and autoask. | ||
290 | The latter requires confirmation like the ask option. | ||
291 | |||
292 | ControlPath | ||
293 | Specify the path to the control socket used for connection | ||
294 | sharing as described in the ControlMaster section above or the | ||
295 | string none to disable connection sharing. Arguments to | ||
296 | ControlPath may use the tilde syntax to refer to a user's home | ||
297 | directory or the tokens described in the TOKENS section. It is | ||
298 | recommended that any ControlPath used for opportunistic | ||
299 | connection sharing include at least %h, %p, and %r (or | ||
300 | alternatively %C) and be placed in a directory that is not | ||
301 | writable by other users. This ensures that shared connections | ||
302 | are uniquely identified. | ||
303 | |||
304 | ControlPersist | ||
305 | When used in conjunction with ControlMaster, specifies that the | ||
306 | master connection should remain open in the background (waiting | ||
307 | for future client connections) after the initial client | ||
308 | connection has been closed. If set to no, then the master | ||
309 | connection will not be placed into the background, and will close | ||
310 | as soon as the initial client connection is closed. If set to | ||
311 | yes or 0, then the master connection will remain in the | ||
312 | background indefinitely (until killed or closed via a mechanism | ||
313 | such as the "ssh -O exit"). If set to a time in seconds, or a | ||
314 | time in any of the formats documented in sshd_config(5), then the | ||
315 | backgrounded master connection will automatically terminate after | ||
316 | it has remained idle (with no client connections) for the | ||
317 | specified time. | ||
318 | |||
319 | DynamicForward | ||
320 | Specifies that a TCP port on the local machine be forwarded over | ||
321 | the secure channel, and the application protocol is then used to | ||
322 | determine where to connect to from the remote machine. | ||
323 | |||
324 | The argument must be [bind_address:]port. IPv6 addresses can be | ||
325 | specified by enclosing addresses in square brackets. By default, | ||
326 | the local port is bound in accordance with the GatewayPorts | ||
327 | setting. However, an explicit bind_address may be used to bind | ||
328 | the connection to a specific address. The bind_address of | ||
329 | localhost indicates that the listening port be bound for local | ||
330 | use only, while an empty address or M-bM-^@M-^X*M-bM-^@M-^Y indicates that the port | ||
331 | should be available from all interfaces. | ||
332 | |||
333 | Currently the SOCKS4 and SOCKS5 protocols are supported, and | ||
334 | ssh(1) will act as a SOCKS server. Multiple forwardings may be | ||
335 | specified, and additional forwardings can be given on the command | ||
336 | line. Only the superuser can forward privileged ports. | ||
337 | |||
338 | EnableSSHKeysign | ||
339 | Setting this option to yes in the global client configuration | ||
340 | file /etc/ssh/ssh_config enables the use of the helper program | ||
341 | ssh-keysign(8) during HostbasedAuthentication. The argument must | ||
342 | be yes or no (the default). This option should be placed in the | ||
343 | non-hostspecific section. See ssh-keysign(8) for more | ||
344 | information. | ||
345 | |||
346 | EscapeChar | ||
347 | Sets the escape character (default: M-bM-^@M-^X~M-bM-^@M-^Y). The escape character | ||
348 | can also be set on the command line. The argument should be a | ||
349 | single character, M-bM-^@M-^X^M-bM-^@M-^Y followed by a letter, or none to disable | ||
350 | the escape character entirely (making the connection transparent | ||
351 | for binary data). | ||
352 | |||
353 | ExitOnForwardFailure | ||
354 | Specifies whether ssh(1) should terminate the connection if it | ||
355 | cannot set up all requested dynamic, tunnel, local, and remote | ||
356 | port forwardings, (e.g. if either end is unable to bind and | ||
357 | listen on a specified port). Note that ExitOnForwardFailure does | ||
358 | not apply to connections made over port forwardings and will not, | ||
359 | for example, cause ssh(1) to exit if TCP connections to the | ||
360 | ultimate forwarding destination fail. The argument must be yes | ||
361 | or no (the default). | ||
362 | |||
363 | FingerprintHash | ||
364 | Specifies the hash algorithm used when displaying key | ||
365 | fingerprints. Valid options are: md5 and sha256 (the default). | ||
366 | |||
367 | ForwardAgent | ||
368 | Specifies whether the connection to the authentication agent (if | ||
369 | any) will be forwarded to the remote machine. The argument must | ||
370 | be yes or no (the default). | ||
371 | |||
372 | Agent forwarding should be enabled with caution. Users with the | ||
373 | ability to bypass file permissions on the remote host (for the | ||
374 | agent's Unix-domain socket) can access the local agent through | ||
375 | the forwarded connection. An attacker cannot obtain key material | ||
376 | from the agent, however they can perform operations on the keys | ||
377 | that enable them to authenticate using the identities loaded into | ||
378 | the agent. | ||
379 | |||
380 | ForwardX11 | ||
381 | Specifies whether X11 connections will be automatically | ||
382 | redirected over the secure channel and DISPLAY set. The argument | ||
383 | must be yes or no (the default). | ||
384 | |||
385 | X11 forwarding should be enabled with caution. Users with the | ||
386 | ability to bypass file permissions on the remote host (for the | ||
387 | user's X11 authorization database) can access the local X11 | ||
388 | display through the forwarded connection. An attacker may then | ||
389 | be able to perform activities such as keystroke monitoring if the | ||
390 | ForwardX11Trusted option is also enabled. | ||
391 | |||
392 | ForwardX11Timeout | ||
393 | Specify a timeout for untrusted X11 forwarding using the format | ||
394 | described in the TIME FORMATS section of sshd_config(5). X11 | ||
395 | connections received by ssh(1) after this time will be refused. | ||
396 | The default is to disable untrusted X11 forwarding after twenty | ||
397 | minutes has elapsed. | ||
398 | |||
399 | ForwardX11Trusted | ||
400 | If this option is set to yes, remote X11 clients will have full | ||
401 | access to the original X11 display. | ||
402 | |||
403 | If this option is set to no (the default), remote X11 clients | ||
404 | will be considered untrusted and prevented from stealing or | ||
405 | tampering with data belonging to trusted X11 clients. | ||
406 | Furthermore, the xauth(1) token used for the session will be set | ||
407 | to expire after 20 minutes. Remote clients will be refused | ||
408 | access after this time. | ||
409 | |||
410 | See the X11 SECURITY extension specification for full details on | ||
411 | the restrictions imposed on untrusted clients. | ||
412 | |||
413 | GatewayPorts | ||
414 | Specifies whether remote hosts are allowed to connect to local | ||
415 | forwarded ports. By default, ssh(1) binds local port forwardings | ||
416 | to the loopback address. This prevents other remote hosts from | ||
417 | connecting to forwarded ports. GatewayPorts can be used to | ||
418 | specify that ssh should bind local port forwardings to the | ||
419 | wildcard address, thus allowing remote hosts to connect to | ||
420 | forwarded ports. The argument must be yes or no (the default). | ||
421 | |||
422 | GlobalKnownHostsFile | ||
423 | Specifies one or more files to use for the global host key | ||
424 | database, separated by whitespace. The default is | ||
425 | /etc/ssh/ssh_known_hosts, /etc/ssh/ssh_known_hosts2. | ||
426 | |||
427 | GSSAPIAuthentication | ||
428 | Specifies whether user authentication based on GSSAPI is allowed. | ||
429 | The default is no. | ||
430 | |||
431 | GSSAPIDelegateCredentials | ||
432 | Forward (delegate) credentials to the server. The default is no. | ||
433 | |||
434 | HashKnownHosts | ||
435 | Indicates that ssh(1) should hash host names and addresses when | ||
436 | they are added to ~/.ssh/known_hosts. These hashed names may be | ||
437 | used normally by ssh(1) and sshd(8), but they do not reveal | ||
438 | identifying information should the file's contents be disclosed. | ||
439 | The default is no. Note that existing names and addresses in | ||
440 | known hosts files will not be converted automatically, but may be | ||
441 | manually hashed using ssh-keygen(1). | ||
442 | |||
443 | HostbasedAuthentication | ||
444 | Specifies whether to try rhosts based authentication with public | ||
445 | key authentication. The argument must be yes or no (the | ||
446 | default). | ||
447 | |||
448 | HostbasedKeyTypes | ||
449 | Specifies the key types that will be used for hostbased | ||
450 | authentication as a comma-separated pattern list. Alternately if | ||
451 | the specified value begins with a M-bM-^@M-^X+M-bM-^@M-^Y character, then the | ||
452 | specified key types will be appended to the default set instead | ||
453 | of replacing them. If the specified value begins with a M-bM-^@M-^X-M-bM-^@M-^Y | ||
454 | character, then the specified key types (including wildcards) | ||
455 | will be removed from the default set instead of replacing them. | ||
456 | The default for this option is: | ||
457 | |||
458 | ecdsa-sha2-nistp256-cert-v01@openssh.com, | ||
459 | ecdsa-sha2-nistp384-cert-v01@openssh.com, | ||
460 | ecdsa-sha2-nistp521-cert-v01@openssh.com, | ||
461 | ssh-ed25519-cert-v01@openssh.com, | ||
462 | ssh-rsa-cert-v01@openssh.com, | ||
463 | ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521, | ||
464 | ssh-ed25519,ssh-rsa | ||
465 | |||
466 | The -Q option of ssh(1) may be used to list supported key types. | ||
467 | |||
468 | HostKeyAlgorithms | ||
469 | Specifies the host key algorithms that the client wants to use in | ||
470 | order of preference. Alternately if the specified value begins | ||
471 | with a M-bM-^@M-^X+M-bM-^@M-^Y character, then the specified key types will be | ||
472 | appended to the default set instead of replacing them. If the | ||
473 | specified value begins with a M-bM-^@M-^X-M-bM-^@M-^Y character, then the specified | ||
474 | key types (including wildcards) will be removed from the default | ||
475 | set instead of replacing them. The default for this option is: | ||
476 | |||
477 | ecdsa-sha2-nistp256-cert-v01@openssh.com, | ||
478 | ecdsa-sha2-nistp384-cert-v01@openssh.com, | ||
479 | ecdsa-sha2-nistp521-cert-v01@openssh.com, | ||
480 | ssh-ed25519-cert-v01@openssh.com, | ||
481 | ssh-rsa-cert-v01@openssh.com, | ||
482 | ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521, | ||
483 | ssh-ed25519,ssh-rsa | ||
484 | |||
485 | If hostkeys are known for the destination host then this default | ||
486 | is modified to prefer their algorithms. | ||
487 | |||
488 | The list of available key types may also be obtained using "ssh | ||
489 | -Q key". | ||
490 | |||
491 | HostKeyAlias | ||
492 | Specifies an alias that should be used instead of the real host | ||
493 | name when looking up or saving the host key in the host key | ||
494 | database files. This option is useful for tunneling SSH | ||
495 | connections or for multiple servers running on a single host. | ||
496 | |||
497 | HostName | ||
498 | Specifies the real host name to log into. This can be used to | ||
499 | specify nicknames or abbreviations for hosts. Arguments to | ||
500 | HostName accept the tokens described in the TOKENS section. | ||
501 | Numeric IP addresses are also permitted (both on the command line | ||
502 | and in HostName specifications). The default is the name given | ||
503 | on the command line. | ||
504 | |||
505 | IdentitiesOnly | ||
506 | Specifies that ssh(1) should only use the authentication identity | ||
507 | and certificate files explicitly configured in the ssh_config | ||
508 | files or passed on the ssh(1) command-line, even if ssh-agent(1) | ||
509 | or a PKCS11Provider offers more identities. The argument to this | ||
510 | keyword must be yes or no (the default). This option is intended | ||
511 | for situations where ssh-agent offers many different identities. | ||
512 | |||
513 | IdentityAgent | ||
514 | Specifies the UNIX-domain socket used to communicate with the | ||
515 | authentication agent. | ||
516 | |||
517 | This option overrides the SSH_AUTH_SOCK environment variable and | ||
518 | can be used to select a specific agent. Setting the socket name | ||
519 | to none disables the use of an authentication agent. If the | ||
520 | string "SSH_AUTH_SOCK" is specified, the location of the socket | ||
521 | will be read from the SSH_AUTH_SOCK environment variable. | ||
522 | |||
523 | Arguments to IdentityAgent may use the tilde syntax to refer to a | ||
524 | user's home directory or the tokens described in the TOKENS | ||
525 | section. | ||
526 | |||
527 | IdentityFile | ||
528 | Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA | ||
529 | authentication identity is read. The default is ~/.ssh/identity | ||
530 | for protocol version 1, and ~/.ssh/id_dsa, ~/.ssh/id_ecdsa, | ||
531 | ~/.ssh/id_ed25519 and ~/.ssh/id_rsa for protocol version 2. | ||
532 | Additionally, any identities represented by the authentication | ||
533 | agent will be used for authentication unless IdentitiesOnly is | ||
534 | set. If no certificates have been explicitly specified by | ||
535 | CertificateFile, ssh(1) will try to load certificate information | ||
536 | from the filename obtained by appending -cert.pub to the path of | ||
537 | a specified IdentityFile. | ||
538 | |||
539 | Arguments to IdentityFile may use the tilde syntax to refer to a | ||
540 | user's home directory or the tokens described in the TOKENS | ||
541 | section. | ||
542 | |||
543 | It is possible to have multiple identity files specified in | ||
544 | configuration files; all these identities will be tried in | ||
545 | sequence. Multiple IdentityFile directives will add to the list | ||
546 | of identities tried (this behaviour differs from that of other | ||
547 | configuration directives). | ||
548 | |||
549 | IdentityFile may be used in conjunction with IdentitiesOnly to | ||
550 | select which identities in an agent are offered during | ||
551 | authentication. IdentityFile may also be used in conjunction | ||
552 | with CertificateFile in order to provide any certificate also | ||
553 | needed for authentication with the identity. | ||
554 | |||
555 | IgnoreUnknown | ||
556 | Specifies a pattern-list of unknown options to be ignored if they | ||
557 | are encountered in configuration parsing. This may be used to | ||
558 | suppress errors if ssh_config contains options that are | ||
559 | unrecognised by ssh(1). It is recommended that IgnoreUnknown be | ||
560 | listed early in the configuration file as it will not be applied | ||
561 | to unknown options that appear before it. | ||
562 | |||
563 | Include | ||
564 | Include the specified configuration file(s). Multiple pathnames | ||
565 | may be specified and each pathname may contain glob(3) wildcards | ||
566 | and, for user configurations, shell-like M-bM-^@M-^X~M-bM-^@M-^Y references to user | ||
567 | home directories. Files without absolute paths are assumed to be | ||
568 | in ~/.ssh if included in a user configuration file or /etc/ssh if | ||
569 | included from the system configuration file. Include directive | ||
570 | may appear inside a Match or Host block to perform conditional | ||
571 | inclusion. | ||
572 | |||
573 | IPQoS Specifies the IPv4 type-of-service or DSCP class for connections. | ||
574 | Accepted values are af11, af12, af13, af21, af22, af23, af31, | ||
575 | af32, af33, af41, af42, af43, cs0, cs1, cs2, cs3, cs4, cs5, cs6, | ||
576 | cs7, ef, lowdelay, throughput, reliability, or a numeric value. | ||
577 | This option may take one or two arguments, separated by | ||
578 | whitespace. If one argument is specified, it is used as the | ||
579 | packet class unconditionally. If two values are specified, the | ||
580 | first is automatically selected for interactive sessions and the | ||
581 | second for non-interactive sessions. The default is lowdelay for | ||
582 | interactive sessions and throughput for non-interactive sessions. | ||
583 | |||
584 | KbdInteractiveAuthentication | ||
585 | Specifies whether to use keyboard-interactive authentication. | ||
586 | The argument to this keyword must be yes (the default) or no. | ||
587 | |||
588 | KbdInteractiveDevices | ||
589 | Specifies the list of methods to use in keyboard-interactive | ||
590 | authentication. Multiple method names must be comma-separated. | ||
591 | The default is to use the server specified list. The methods | ||
592 | available vary depending on what the server supports. For an | ||
593 | OpenSSH server, it may be zero or more of: bsdauth, pam, and | ||
594 | skey. | ||
595 | |||
596 | KexAlgorithms | ||
597 | Specifies the available KEX (Key Exchange) algorithms. Multiple | ||
598 | algorithms must be comma-separated. Alternately if the specified | ||
599 | value begins with a M-bM-^@M-^X+M-bM-^@M-^Y character, then the specified methods | ||
600 | will be appended to the default set instead of replacing them. | ||
601 | If the specified value begins with a M-bM-^@M-^X-M-bM-^@M-^Y character, then the | ||
602 | specified methods (including wildcards) will be removed from the | ||
603 | default set instead of replacing them. The default is: | ||
604 | |||
605 | curve25519-sha256,curve25519-sha256@libssh.org, | ||
606 | ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521, | ||
607 | diffie-hellman-group-exchange-sha256, | ||
608 | diffie-hellman-group-exchange-sha1, | ||
609 | diffie-hellman-group14-sha1 | ||
610 | |||
611 | The list of available key exchange algorithms may also be | ||
612 | obtained using "ssh -Q kex". | ||
613 | |||
614 | LocalCommand | ||
615 | Specifies a command to execute on the local machine after | ||
616 | successfully connecting to the server. The command string | ||
617 | extends to the end of the line, and is executed with the user's | ||
618 | shell. Arguments to LocalCommand accept the tokens described in | ||
619 | the TOKENS section. | ||
620 | |||
621 | The command is run synchronously and does not have access to the | ||
622 | session of the ssh(1) that spawned it. It should not be used for | ||
623 | interactive commands. | ||
624 | |||
625 | This directive is ignored unless PermitLocalCommand has been | ||
626 | enabled. | ||
627 | |||
628 | LocalForward | ||
629 | Specifies that a TCP port on the local machine be forwarded over | ||
630 | the secure channel to the specified host and port from the remote | ||
631 | machine. The first argument must be [bind_address:]port and the | ||
632 | second argument must be host:hostport. IPv6 addresses can be | ||
633 | specified by enclosing addresses in square brackets. Multiple | ||
634 | forwardings may be specified, and additional forwardings can be | ||
635 | given on the command line. Only the superuser can forward | ||
636 | privileged ports. By default, the local port is bound in | ||
637 | accordance with the GatewayPorts setting. However, an explicit | ||
638 | bind_address may be used to bind the connection to a specific | ||
639 | address. The bind_address of localhost indicates that the | ||
640 | listening port be bound for local use only, while an empty | ||
641 | address or M-bM-^@M-^X*M-bM-^@M-^Y indicates that the port should be available from | ||
642 | all interfaces. | ||
643 | |||
644 | LogLevel | ||
645 | Gives the verbosity level that is used when logging messages from | ||
646 | ssh(1). The possible values are: QUIET, FATAL, ERROR, INFO, | ||
647 | VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO. | ||
648 | DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify | ||
649 | higher levels of verbose output. | ||
650 | |||
651 | MACs Specifies the MAC (message authentication code) algorithms in | ||
652 | order of preference. The MAC algorithm is used for data | ||
653 | integrity protection. Multiple algorithms must be comma- | ||
654 | separated. If the specified value begins with a M-bM-^@M-^X+M-bM-^@M-^Y character, | ||
655 | then the specified algorithms will be appended to the default set | ||
656 | instead of replacing them. If the specified value begins with a | ||
657 | M-bM-^@M-^X-M-bM-^@M-^Y character, then the specified algorithms (including | ||
658 | wildcards) will be removed from the default set instead of | ||
659 | replacing them. | ||
660 | |||
661 | The algorithms that contain "-etm" calculate the MAC after | ||
662 | encryption (encrypt-then-mac). These are considered safer and | ||
663 | their use recommended. | ||
664 | |||
665 | The default is: | ||
666 | |||
667 | umac-64-etm@openssh.com,umac-128-etm@openssh.com, | ||
668 | hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com, | ||
669 | hmac-sha1-etm@openssh.com, | ||
670 | umac-64@openssh.com,umac-128@openssh.com, | ||
671 | hmac-sha2-256,hmac-sha2-512,hmac-sha1 | ||
672 | |||
673 | The list of available MAC algorithms may also be obtained using | ||
674 | "ssh -Q mac". | ||
675 | |||
676 | NoHostAuthenticationForLocalhost | ||
677 | This option can be used if the home directory is shared across | ||
678 | machines. In this case localhost will refer to a different | ||
679 | machine on each of the machines and the user will get many | ||
680 | warnings about changed host keys. However, this option disables | ||
681 | host authentication for localhost. The argument to this keyword | ||
682 | must be yes or no (the default). | ||
683 | |||
684 | NumberOfPasswordPrompts | ||
685 | Specifies the number of password prompts before giving up. The | ||
686 | argument to this keyword must be an integer. The default is 3. | ||
687 | |||
688 | PasswordAuthentication | ||
689 | Specifies whether to use password authentication. The argument | ||
690 | to this keyword must be yes (the default) or no. | ||
691 | |||
692 | PermitLocalCommand | ||
693 | Allow local command execution via the LocalCommand option or | ||
694 | using the !command escape sequence in ssh(1). The argument must | ||
695 | be yes or no (the default). | ||
696 | |||
697 | PKCS11Provider | ||
698 | Specifies which PKCS#11 provider to use. The argument to this | ||
699 | keyword is the PKCS#11 shared library ssh(1) should use to | ||
700 | communicate with a PKCS#11 token providing the user's private RSA | ||
701 | key. | ||
702 | |||
703 | Port Specifies the port number to connect on the remote host. The | ||
704 | default is 22. | ||
705 | |||
706 | PreferredAuthentications | ||
707 | Specifies the order in which the client should try authentication | ||
708 | methods. This allows a client to prefer one method (e.g. | ||
709 | keyboard-interactive) over another method (e.g. password). The | ||
710 | default is: | ||
711 | |||
712 | gssapi-with-mic,hostbased,publickey, | ||
713 | keyboard-interactive,password | ||
714 | |||
715 | Protocol | ||
716 | Specifies the protocol versions ssh(1) should support in order of | ||
717 | preference. The possible values are 1 and 2. Multiple versions | ||
718 | must be comma-separated. When this option is set to 2,1 ssh will | ||
719 | try version 2 and fall back to version 1 if version 2 is not | ||
720 | available. The default is version 2. Protocol 1 suffers from a | ||
721 | number of cryptographic weaknesses and should not be used. It is | ||
722 | only offered to support legacy devices. | ||
723 | |||
724 | ProxyCommand | ||
725 | Specifies the command to use to connect to the server. The | ||
726 | command string extends to the end of the line, and is executed | ||
727 | using the user's shell M-bM-^@M-^XexecM-bM-^@M-^Y directive to avoid a lingering | ||
728 | shell process. | ||
729 | |||
730 | Arguments to ProxyCommand accept the tokens described in the | ||
731 | TOKENS section. The command can be basically anything, and | ||
732 | should read from its standard input and write to its standard | ||
733 | output. It should eventually connect an sshd(8) server running | ||
734 | on some machine, or execute sshd -i somewhere. Host key | ||
735 | management will be done using the HostName of the host being | ||
736 | connected (defaulting to the name typed by the user). Setting | ||
737 | the command to none disables this option entirely. Note that | ||
738 | CheckHostIP is not available for connects with a proxy command. | ||
739 | |||
740 | This directive is useful in conjunction with nc(1) and its proxy | ||
741 | support. For example, the following directive would connect via | ||
742 | an HTTP proxy at 192.0.2.0: | ||
743 | |||
744 | ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p | ||
745 | |||
746 | ProxyJump | ||
747 | Specifies one or more jump proxies as [user@]host[:port]. | ||
748 | Multiple proxies may be separated by comma characters and will be | ||
749 | visited sequentially. Setting this option will cause ssh(1) to | ||
750 | connect to the target host by first making a ssh(1) connection to | ||
751 | the specified ProxyJump host and then establishing a TCP | ||
752 | forwarding to the ultimate target from there. | ||
753 | |||
754 | Note that this option will compete with the ProxyCommand option - | ||
755 | whichever is specified first will prevent later instances of the | ||
756 | other from taking effect. | ||
757 | |||
758 | ProxyUseFdpass | ||
759 | Specifies that ProxyCommand will pass a connected file descriptor | ||
760 | back to ssh(1) instead of continuing to execute and pass data. | ||
761 | The default is no. | ||
762 | |||
763 | PubkeyAcceptedKeyTypes | ||
764 | Specifies the key types that will be used for public key | ||
765 | authentication as a comma-separated pattern list. Alternately if | ||
766 | the specified value begins with a M-bM-^@M-^X+M-bM-^@M-^Y character, then the key | ||
767 | types after it will be appended to the default instead of | ||
768 | replacing it. If the specified value begins with a M-bM-^@M-^X-M-bM-^@M-^Y | ||
769 | character, then the specified key types (including wildcards) | ||
770 | will be removed from the default set instead of replacing them. | ||
771 | The default for this option is: | ||
772 | |||
773 | ecdsa-sha2-nistp256-cert-v01@openssh.com, | ||
774 | ecdsa-sha2-nistp384-cert-v01@openssh.com, | ||
775 | ecdsa-sha2-nistp521-cert-v01@openssh.com, | ||
776 | ssh-ed25519-cert-v01@openssh.com, | ||
777 | ssh-rsa-cert-v01@openssh.com, | ||
778 | ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521, | ||
779 | ssh-ed25519,ssh-rsa | ||
780 | |||
781 | The list of available key types may also be obtained using "ssh | ||
782 | -Q key". | ||
783 | |||
784 | PubkeyAuthentication | ||
785 | Specifies whether to try public key authentication. The argument | ||
786 | to this keyword must be yes (the default) or no. | ||
787 | |||
788 | RekeyLimit | ||
789 | Specifies the maximum amount of data that may be transmitted | ||
790 | before the session key is renegotiated, optionally followed a | ||
791 | maximum amount of time that may pass before the session key is | ||
792 | renegotiated. The first argument is specified in bytes and may | ||
793 | have a suffix of M-bM-^@M-^XKM-bM-^@M-^Y, M-bM-^@M-^XMM-bM-^@M-^Y, or M-bM-^@M-^XGM-bM-^@M-^Y to indicate Kilobytes, | ||
794 | Megabytes, or Gigabytes, respectively. The default is between | ||
795 | M-bM-^@M-^X1GM-bM-^@M-^Y and M-bM-^@M-^X4GM-bM-^@M-^Y, depending on the cipher. The optional second | ||
796 | value is specified in seconds and may use any of the units | ||
797 | documented in the TIME FORMATS section of sshd_config(5). The | ||
798 | default value for RekeyLimit is default none, which means that | ||
799 | rekeying is performed after the cipher's default amount of data | ||
800 | has been sent or received and no time based rekeying is done. | ||
801 | |||
802 | RemoteForward | ||
803 | Specifies that a TCP port on the remote machine be forwarded over | ||
804 | the secure channel to the specified host and port from the local | ||
805 | machine. The first argument must be [bind_address:]port and the | ||
806 | second argument must be host:hostport. IPv6 addresses can be | ||
807 | specified by enclosing addresses in square brackets. Multiple | ||
808 | forwardings may be specified, and additional forwardings can be | ||
809 | given on the command line. Privileged ports can be forwarded | ||
810 | only when logging in as root on the remote machine. | ||
811 | |||
812 | If the port argument is 0, the listen port will be dynamically | ||
813 | allocated on the server and reported to the client at run time. | ||
814 | |||
815 | If the bind_address is not specified, the default is to only bind | ||
816 | to loopback addresses. If the bind_address is M-bM-^@M-^X*M-bM-^@M-^Y or an empty | ||
817 | string, then the forwarding is requested to listen on all | ||
818 | interfaces. Specifying a remote bind_address will only succeed | ||
819 | if the server's GatewayPorts option is enabled (see | ||
820 | sshd_config(5)). | ||
821 | |||
822 | RequestTTY | ||
823 | Specifies whether to request a pseudo-tty for the session. The | ||
824 | argument may be one of: no (never request a TTY), yes (always | ||
825 | request a TTY when standard input is a TTY), force (always | ||
826 | request a TTY) or auto (request a TTY when opening a login | ||
827 | session). This option mirrors the -t and -T flags for ssh(1). | ||
828 | |||
829 | RevokedHostKeys | ||
830 | Specifies revoked host public keys. Keys listed in this file | ||
831 | will be refused for host authentication. Note that if this file | ||
832 | does not exist or is not readable, then host authentication will | ||
833 | be refused for all hosts. Keys may be specified as a text file, | ||
834 | listing one public key per line, or as an OpenSSH Key Revocation | ||
835 | List (KRL) as generated by ssh-keygen(1). For more information | ||
836 | on KRLs, see the KEY REVOCATION LISTS section in ssh-keygen(1). | ||
837 | |||
838 | RhostsRSAAuthentication | ||
839 | Specifies whether to try rhosts based authentication with RSA | ||
840 | host authentication. The argument must be yes or no (the | ||
841 | default). This option applies to protocol version 1 only and | ||
842 | requires ssh(1) to be setuid root. | ||
843 | |||
844 | RSAAuthentication | ||
845 | Specifies whether to try RSA authentication. The argument to | ||
846 | this keyword must be yes (the default) or no. RSA authentication | ||
847 | will only be attempted if the identity file exists, or an | ||
848 | authentication agent is running. Note that this option applies | ||
849 | to protocol version 1 only. | ||
850 | |||
851 | SendEnv | ||
852 | Specifies what variables from the local environ(7) should be sent | ||
853 | to the server. The server must also support it, and the server | ||
854 | must be configured to accept these environment variables. Note | ||
855 | that the TERM environment variable is always sent whenever a | ||
856 | pseudo-terminal is requested as it is required by the protocol. | ||
857 | Refer to AcceptEnv in sshd_config(5) for how to configure the | ||
858 | server. Variables are specified by name, which may contain | ||
859 | wildcard characters. Multiple environment variables may be | ||
860 | separated by whitespace or spread across multiple SendEnv | ||
861 | directives. The default is not to send any environment | ||
862 | variables. | ||
863 | |||
864 | See PATTERNS for more information on patterns. | ||
865 | |||
866 | ServerAliveCountMax | ||
867 | Sets the number of server alive messages (see below) which may be | ||
868 | sent without ssh(1) receiving any messages back from the server. | ||
869 | If this threshold is reached while server alive messages are | ||
870 | being sent, ssh will disconnect from the server, terminating the | ||
871 | session. It is important to note that the use of server alive | ||
872 | messages is very different from TCPKeepAlive (below). The server | ||
873 | alive messages are sent through the encrypted channel and | ||
874 | therefore will not be spoofable. The TCP keepalive option | ||
875 | enabled by TCPKeepAlive is spoofable. The server alive mechanism | ||
876 | is valuable when the client or server depend on knowing when a | ||
877 | connection has become inactive. | ||
878 | |||
879 | The default value is 3. If, for example, ServerAliveInterval | ||
880 | (see below) is set to 15 and ServerAliveCountMax is left at the | ||
881 | default, if the server becomes unresponsive, ssh will disconnect | ||
882 | after approximately 45 seconds. | ||
883 | |||
884 | ServerAliveInterval | ||
885 | Sets a timeout interval in seconds after which if no data has | ||
886 | been received from the server, ssh(1) will send a message through | ||
887 | the encrypted channel to request a response from the server. The | ||
888 | default is 0, indicating that these messages will not be sent to | ||
889 | the server. | ||
890 | |||
891 | StreamLocalBindMask | ||
892 | Sets the octal file creation mode mask (umask) used when creating | ||
893 | a Unix-domain socket file for local or remote port forwarding. | ||
894 | This option is only used for port forwarding to a Unix-domain | ||
895 | socket file. | ||
896 | |||
897 | The default value is 0177, which creates a Unix-domain socket | ||
898 | file that is readable and writable only by the owner. Note that | ||
899 | not all operating systems honor the file mode on Unix-domain | ||
900 | socket files. | ||
901 | |||
902 | StreamLocalBindUnlink | ||
903 | Specifies whether to remove an existing Unix-domain socket file | ||
904 | for local or remote port forwarding before creating a new one. | ||
905 | If the socket file already exists and StreamLocalBindUnlink is | ||
906 | not enabled, ssh will be unable to forward the port to the Unix- | ||
907 | domain socket file. This option is only used for port forwarding | ||
908 | to a Unix-domain socket file. | ||
909 | |||
910 | The argument must be yes or no (the default). | ||
911 | |||
912 | StrictHostKeyChecking | ||
913 | If this flag is set to yes, ssh(1) will never automatically add | ||
914 | host keys to the ~/.ssh/known_hosts file, and refuses to connect | ||
915 | to hosts whose host key has changed. This provides maximum | ||
916 | protection against trojan horse attacks, though it can be | ||
917 | annoying when the /etc/ssh/ssh_known_hosts file is poorly | ||
918 | maintained or when connections to new hosts are frequently made. | ||
919 | This option forces the user to manually add all new hosts. If | ||
920 | this flag is set to no, ssh will automatically add new host keys | ||
921 | to the user known hosts files. If this flag is set to ask (the | ||
922 | default), new host keys will be added to the user known host | ||
923 | files only after the user has confirmed that is what they really | ||
924 | want to do, and ssh will refuse to connect to hosts whose host | ||
925 | key has changed. The host keys of known hosts will be verified | ||
926 | automatically in all cases. | ||
927 | |||
928 | TCPKeepAlive | ||
929 | Specifies whether the system should send TCP keepalive messages | ||
930 | to the other side. If they are sent, death of the connection or | ||
931 | crash of one of the machines will be properly noticed. However, | ||
932 | this means that connections will die if the route is down | ||
933 | temporarily, and some people find it annoying. | ||
934 | |||
935 | The default is yes (to send TCP keepalive messages), and the | ||
936 | client will notice if the network goes down or the remote host | ||
937 | dies. This is important in scripts, and many users want it too. | ||
938 | |||
939 | To disable TCP keepalive messages, the value should be set to no. | ||
940 | |||
941 | Tunnel Request tun(4) device forwarding between the client and the | ||
942 | server. The argument must be yes, point-to-point (layer 3), | ||
943 | ethernet (layer 2), or no (the default). Specifying yes requests | ||
944 | the default tunnel mode, which is point-to-point. | ||
945 | |||
946 | TunnelDevice | ||
947 | Specifies the tun(4) devices to open on the client (local_tun) | ||
948 | and the server (remote_tun). | ||
949 | |||
950 | The argument must be local_tun[:remote_tun]. The devices may be | ||
951 | specified by numerical ID or the keyword any, which uses the next | ||
952 | available tunnel device. If remote_tun is not specified, it | ||
953 | defaults to any. The default is any:any. | ||
954 | |||
955 | UpdateHostKeys | ||
956 | Specifies whether ssh(1) should accept notifications of | ||
957 | additional hostkeys from the server sent after authentication has | ||
958 | completed and add them to UserKnownHostsFile. The argument must | ||
959 | be yes, no (the default) or ask. Enabling this option allows | ||
960 | learning alternate hostkeys for a server and supports graceful | ||
961 | key rotation by allowing a server to send replacement public keys | ||
962 | before old ones are removed. Additional hostkeys are only | ||
963 | accepted if the key used to authenticate the host was already | ||
964 | trusted or explicitly accepted by the user. If UpdateHostKeys is | ||
965 | set to ask, then the user is asked to confirm the modifications | ||
966 | to the known_hosts file. Confirmation is currently incompatible | ||
967 | with ControlPersist, and will be disabled if it is enabled. | ||
968 | |||
969 | Presently, only sshd(8) from OpenSSH 6.8 and greater support the | ||
970 | "hostkeys@openssh.com" protocol extension used to inform the | ||
971 | client of all the server's hostkeys. | ||
972 | |||
973 | UsePrivilegedPort | ||
974 | Specifies whether to use a privileged port for outgoing | ||
975 | connections. The argument must be yes or no (the default). If | ||
976 | set to yes, ssh(1) must be setuid root. Note that this option | ||
977 | must be set to yes for RhostsRSAAuthentication with older | ||
978 | servers. | ||
979 | |||
980 | User Specifies the user to log in as. This can be useful when a | ||
981 | different user name is used on different machines. This saves | ||
982 | the trouble of having to remember to give the user name on the | ||
983 | command line. | ||
984 | |||
985 | UserKnownHostsFile | ||
986 | Specifies one or more files to use for the user host key | ||
987 | database, separated by whitespace. The default is | ||
988 | ~/.ssh/known_hosts, ~/.ssh/known_hosts2. | ||
989 | |||
990 | VerifyHostKeyDNS | ||
991 | Specifies whether to verify the remote key using DNS and SSHFP | ||
992 | resource records. If this option is set to yes, the client will | ||
993 | implicitly trust keys that match a secure fingerprint from DNS. | ||
994 | Insecure fingerprints will be handled as if this option was set | ||
995 | to ask. If this option is set to ask, information on fingerprint | ||
996 | match will be displayed, but the user will still need to confirm | ||
997 | new host keys according to the StrictHostKeyChecking option. The | ||
998 | default is no. | ||
999 | |||
1000 | See also VERIFYING HOST KEYS in ssh(1). | ||
1001 | |||
1002 | VisualHostKey | ||
1003 | If this flag is set to yes, an ASCII art representation of the | ||
1004 | remote host key fingerprint is printed in addition to the | ||
1005 | fingerprint string at login and for unknown host keys. If this | ||
1006 | flag is set to no (the default), no fingerprint strings are | ||
1007 | printed at login and only the fingerprint string will be printed | ||
1008 | for unknown host keys. | ||
1009 | |||
1010 | XAuthLocation | ||
1011 | Specifies the full pathname of the xauth(1) program. The default | ||
1012 | is /usr/X11R6/bin/xauth. | ||
1013 | |||
1014 | PATTERNS | ||
1015 | A pattern consists of zero or more non-whitespace characters, M-bM-^@M-^X*M-bM-^@M-^Y (a | ||
1016 | wildcard that matches zero or more characters), or M-bM-^@M-^X?M-bM-^@M-^Y (a wildcard that | ||
1017 | matches exactly one character). For example, to specify a set of | ||
1018 | declarations for any host in the ".co.uk" set of domains, the following | ||
1019 | pattern could be used: | ||
1020 | |||
1021 | Host *.co.uk | ||
1022 | |||
1023 | The following pattern would match any host in the 192.168.0.[0-9] network | ||
1024 | range: | ||
1025 | |||
1026 | Host 192.168.0.? | ||
1027 | |||
1028 | A pattern-list is a comma-separated list of patterns. Patterns within | ||
1029 | pattern-lists may be negated by preceding them with an exclamation mark | ||
1030 | (M-bM-^@M-^X!M-bM-^@M-^Y). For example, to allow a key to be used from anywhere within an | ||
1031 | organization except from the "dialup" pool, the following entry (in | ||
1032 | authorized_keys) could be used: | ||
1033 | |||
1034 | from="!*.dialup.example.com,*.example.com" | ||
1035 | |||
1036 | TOKENS | ||
1037 | Arguments to some keywords can make use of tokens, which are expanded at | ||
1038 | runtime: | ||
1039 | |||
1040 | %% A literal M-bM-^@M-^X%M-bM-^@M-^Y. | ||
1041 | %C Shorthand for %l%h%p%r. | ||
1042 | %d Local user's home directory. | ||
1043 | %h The remote hostname. | ||
1044 | %i The local user ID. | ||
1045 | %L The local hostname. | ||
1046 | %l The local hostname, including the domain name. | ||
1047 | %n The original remote hostname, as given on the command line. | ||
1048 | %p The remote port. | ||
1049 | %r The remote username. | ||
1050 | %u The local username. | ||
1051 | |||
1052 | Match exec accepts the tokens %%, %h, %L, %l, %n, %p, %r, and %u. | ||
1053 | |||
1054 | CertificateFile accepts the tokens %%, %d, %h, %l, %r, and %u. | ||
1055 | |||
1056 | ControlPath accepts the tokens %%, %C, %h, %i, %L, %l, %n, %p, %r, and | ||
1057 | %u. | ||
1058 | |||
1059 | HostName accepts the tokens %% and %h. | ||
1060 | |||
1061 | IdentityAgent and IdentityFile accept the tokens %%, %d, %h, %l, %r, and | ||
1062 | %u. | ||
1063 | |||
1064 | LocalCommand accepts the tokens %%, %C, %d, %h, %l, %n, %p, %r, and %u. | ||
1065 | |||
1066 | ProxyCommand accepts the tokens %%, %h, %p, and %r. | ||
1067 | |||
1068 | FILES | ||
1069 | ~/.ssh/config | ||
1070 | This is the per-user configuration file. The format of this file | ||
1071 | is described above. This file is used by the SSH client. | ||
1072 | Because of the potential for abuse, this file must have strict | ||
1073 | permissions: read/write for the user, and not accessible by | ||
1074 | others. | ||
1075 | |||
1076 | /etc/ssh/ssh_config | ||
1077 | Systemwide configuration file. This file provides defaults for | ||
1078 | those values that are not specified in the user's configuration | ||
1079 | file, and for those users who do not have a configuration file. | ||
1080 | This file must be world-readable. | ||
1081 | |||
1082 | SEE ALSO | ||
1083 | ssh(1) | ||
1084 | |||
1085 | AUTHORS | ||
1086 | OpenSSH is a derivative of the original and free ssh 1.2.12 release by | ||
1087 | Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo | ||
1088 | de Raadt and Dug Song removed many bugs, re-added newer features and | ||
1089 | created OpenSSH. Markus Friedl contributed the support for SSH protocol | ||
1090 | versions 1.5 and 2.0. | ||
1091 | |||
1092 | OpenBSD 6.0 February 27, 2017 OpenBSD 6.0 | ||