1SSH_CONFIG(5) BSD File Formats Manual SSH_CONFIG(5)
2
4 ssh_config — OpenSSH SSH client configuration files
5
7 ~/.ssh/config
8 /etc/ssh/ssh_config
9
11 ssh(1) obtains configuration data from the following sources in the fol‐
12 lowing order:
13 1. command-line options
15 2. user's configuration file (~/.ssh/config)
16 3. system-wide configuration file (/etc/ssh/ssh_config)
17 For each parameter, the first obtained value will be used. The configu‐
19 ration files contain sections separated by “Host” specifications, and
20 that section is only applied for hosts that match one of the patterns
21 given in the specification. The matched host name is the one given on
22 the command line.
23 Since the first obtained value for each parameter is used, more host-spe‐
25 cific declarations should be given near the beginning of the file, and
26 general defaults at the end.
27 The configuration file has the following format:
29 Empty lines and lines starting with ‘#’ are comments. Otherwise a line
31 is of the format “keyword arguments”. Configuration options may be sepa‐
32 rated by whitespace or optional whitespace and exactly one ‘=’; the lat‐
33 ter format is useful to avoid the need to quote whitespace when specify‐
34 ing configuration options using the ssh, scp, and sftp -o option. Argu‐
35 ments may optionally be enclosed in double quotes (") in order to repre‐
36 sent arguments containing spaces.
37 The possible keywords and their meanings are as follows (note that key‐
39 words are case-insensitive and arguments are case-sensitive):
40 Host Restricts the following declarations (up to the next Host key‐
42 word) to be only for those hosts that match one of the patterns
43 given after the keyword. If more than one pattern is provided,
44 they should be separated by whitespace. A single ‘*’ as a pat‐
45 tern can be used to provide global defaults for all hosts. The
46 host is the hostname argument given on the command line (i.e. the
47 name is not converted to a canonicalized host name before match‐
48 ing).
49 See PATTERNS for more information on patterns.
51 AddressFamily
53 Specifies which address family to use when connecting. Valid
54 arguments are “any”, “inet” (use IPv4 only), or “inet6” (use IPv6
55 only).
56 BatchMode
58 If set to “yes”, passphrase/password querying will be disabled.
59 This option is useful in scripts and other batch jobs where no
60 user is present to supply the password. The argument must be
61 “yes” or “no”. The default is “no”.
62 BindAddress
64 Use the specified address on the local machine as the source
65 address of the connection. Only useful on systems with more than
66 one address. Note that this option does not work if
67 UsePrivilegedPort is set to “yes”.
68 ChallengeResponseAuthentication
70 Specifies whether to use challenge-response authentication. The
71 argument to this keyword must be “yes” or “no”. The default is
72 “yes”.
73 CheckHostIP
75 If this flag is set to “yes”, ssh(1) will additionally check the
76 host IP address in the known_hosts file. This allows ssh to
77 detect if a host key changed due to DNS spoofing. If the option
78 is set to “no”, the check will not be executed. The default is
79 “yes”.
80 Cipher Specifies the cipher to use for encrypting the session in proto‐
82 col version 1. Currently, “blowfish”, “3des”, and “des” are sup‐
83 ported. des is only supported in the ssh(1) client for interop‐
84 erability with legacy protocol 1 implementations that do not sup‐
85 port the 3des cipher. Its use is strongly discouraged due to
86 cryptographic weaknesses. The default is “3des”.
87 Ciphers
89 Specifies the ciphers allowed for protocol version 2 in order of
90 preference. Multiple ciphers must be comma-separated. The sup‐
91 ported ciphers are “3des-cbc”, “aes128-cbc”, “aes192-cbc”,
92 “aes256-cbc”, “aes128-ctr”, “aes192-ctr”, “aes256-ctr”,
93 “arcfour128”, “arcfour256”, “arcfour”, “blowfish-cbc”, and
94 “cast128-cbc”. The default is:
95 aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
97 aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
98 aes256-cbc,arcfour
99 ClearAllForwardings
101 Specifies that all local, remote, and dynamic port forwardings
102 specified in the configuration files or on the command line be
103 cleared. This option is primarily useful when used from the
104 ssh(1) command line to clear port forwardings set in configura‐
105 tion files, and is automatically set by scp(1) and sftp(1). The
106 argument must be “yes” or “no”. The default is “no”.
107 Compression
109 Specifies whether to use compression. The argument must be “yes”
110 or “no”. The default is “no”.
111 CompressionLevel
113 Specifies the compression level to use if compression is enabled.
114 The argument must be an integer from 1 (fast) to 9 (slow, best).
115 The default level is 6, which is good for most applications. The
116 meaning of the values is the same as in gzip(1). Note that this
117 option applies to protocol version 1 only.
118 ConnectionAttempts
120 Specifies the number of tries (one per second) to make before
121 exiting. The argument must be an integer. This may be useful in
122 scripts if the connection sometimes fails. The default is 1.
123 ConnectTimeout
125 Specifies the timeout (in seconds) used when connecting to the
126 SSH server, instead of using the default system TCP timeout.
127 This value is used only when the target is down or really
128 unreachable, not when it refuses the connection.
129 ControlMaster
131 Enables the sharing of multiple sessions over a single network
132 connection. When set to “yes”, ssh(1) will listen for connec‐
133 tions on a control socket specified using the ControlPath argu‐
134 ment. Additional sessions can connect to this socket using the
135 same ControlPath with ControlMaster set to “no” (the default).
136 These sessions will try to reuse the master instance's network
137 connection rather than initiating new ones, but will fall back to
138 connecting normally if the control socket does not exist, or is
139 not listening.
140 Setting this to “ask” will cause ssh to listen for control con‐
142 nections, but require confirmation using the SSH_ASKPASS program
143 before they are accepted (see ssh-add(1) for details). If the
144 ControlPath cannot be opened, ssh will continue without connect‐
145 ing to a master instance.
146 X11 and ssh-agent(1) forwarding is supported over these multi‐
148 plexed connections, however the display and agent forwarded will
149 be the one belonging to the master connection i.e. it is not pos‐
150 sible to forward multiple displays or agents.
151 Two additional options allow for opportunistic multiplexing: try
153 to use a master connection but fall back to creating a new one if
154 one does not already exist. These options are: “auto” and
155 “autoask”. The latter requires confirmation like the “ask”
156 option.
157 ControlPath
159 Specify the path to the control socket used for connection shar‐
160 ing as described in the ControlMaster section above or the string
161 “none” to disable connection sharing. In the path, ‘%l’ will be
162 substituted by the local host name, ‘%h’ will be substituted by
163 the target host name, ‘%p’ the port, and ‘%r’ by the remote login
164 username. It is recommended that any ControlPath used for oppor‐
165 tunistic connection sharing include at least %h, %p, and %r.
166 This ensures that shared connections are uniquely identified.
167 DynamicForward
169 Specifies that a TCP port on the local machine be forwarded over
170 the secure channel, and the application protocol is then used to
171 determine where to connect to from the remote machine.
172 The argument must be [bind_address:]port. IPv6 addresses can be
174 specified by enclosing addresses in square brackets or by using
175 an alternative syntax: [bind_address/]port. By default, the
176 local port is bound in accordance with the GatewayPorts setting.
177 However, an explicit bind_address may be used to bind the connec‐
178 tion to a specific address. The bind_address of “localhost”
179 indicates that the listening port be bound for local use only,
180 while an empty address or ‘*’ indicates that the port should be
181 available from all interfaces.
182 Currently the SOCKS4 and SOCKS5 protocols are supported, and
184 ssh(1) will act as a SOCKS server. Multiple forwardings may be
185 specified, and additional forwardings can be given on the command
186 line. Only the superuser can forward privileged ports.
187 EnableSSHKeysign
189 Setting this option to “yes” in the global client configuration
190 file /etc/ssh/ssh_config enables the use of the helper program
191 ssh-keysign(8) during HostbasedAuthentication. The argument must
192 be “yes” or “no”. The default is “no”. This option should be
193 placed in the non-hostspecific section. See ssh-keysign(8) for
194 more information.
195 EscapeChar
197 Sets the escape character (default: ‘~’). The escape character
198 can also be set on the command line. The argument should be a
199 single character, ‘^’ followed by a letter, or “none” to disable
200 the escape character entirely (making the connection transparent
201 for binary data).
202 ExitOnForwardFailure
204 Specifies whether ssh(1) should terminate the connection if it
205 cannot set up all requested dynamic, tunnel, local, and remote
206 port forwardings. The argument must be “yes” or “no”. The
207 default is “no”.
208 ForwardAgent
210 Specifies whether the connection to the authentication agent (if
211 any) will be forwarded to the remote machine. The argument must
212 be “yes” or “no”. The default is “no”.
213 Agent forwarding should be enabled with caution. Users with the
215 ability to bypass file permissions on the remote host (for the
216 agent's Unix-domain socket) can access the local agent through
217 the forwarded connection. An attacker cannot obtain key material
218 from the agent, however they can perform operations on the keys
219 that enable them to authenticate using the identities loaded into
220 the agent.
221 ForwardX11
223 Specifies whether X11 connections will be automatically redi‐
224 rected over the secure channel and DISPLAY set. The argument
225 must be “yes” or “no”. The default is “no”.
226 X11 forwarding should be enabled with caution. Users with the
228 ability to bypass file permissions on the remote host (for the
229 user's X11 authorization database) can access the local X11 dis‐
230 play through the forwarded connection. An attacker may then be
231 able to perform activities such as keystroke monitoring if the
232 ForwardX11Trusted option is also enabled.
233 ForwardX11Trusted
235 If this option is set to “yes”, remote X11 clients will have full
236 access to the original X11 display.
237 If this option is set to “no”, remote X11 clients will be consid‐
239 ered untrusted and prevented from stealing or tampering with data
240 belonging to trusted X11 clients. Furthermore, the xauth(1)
241 token used for the session will be set to expire after 20 min‐
242 utes. Remote clients will be refused access after this time.
243 The default is “no”.
245 See the X11 SECURITY extension specification for full details on
247 the restrictions imposed on untrusted clients.
248 GatewayPorts
250 Specifies whether remote hosts are allowed to connect to local
251 forwarded ports. By default, ssh(1) binds local port forwardings
252 to the loopback address. This prevents other remote hosts from
253 connecting to forwarded ports. GatewayPorts can be used to spec‐
254 ify that ssh should bind local port forwardings to the wildcard
255 address, thus allowing remote hosts to connect to forwarded
256 ports. The argument must be “yes” or “no”. The default is “no”.
257 GlobalKnownHostsFile
259 Specifies a file to use for the global host key database instead
260 of /etc/ssh/ssh_known_hosts.
261 GSSAPIAuthentication
263 Specifies whether user authentication based on GSSAPI is allowed.
264 The default is “no”. Note that this option applies to protocol
265 version 2 only.
266 GSSAPIKeyExchange
268 Specifies whether key exchange based on GSSAPI may be used. When
269 using GSSAPI key exchange the server need not have a host key.
270 The default is “no”. Note that this option applies to protocol
271 version 2 only.
272 GSSAPIClientIdentity
274 If set, specifies the GSSAPI client identity that ssh should use
275 when connecting to the server. The default is unset, which means
276 that the default identity will be used.
277 GSSAPIDelegateCredentials
279 Forward (delegate) credentials to the server. The default is
280 “no”. Note that this option applies to protocol version 2 con‐
281 nections using GSSAPI.
282 GSSAPIRenewalForcesRekey
284 If set to “yes” then renewal of the client's GSSAPI credentials
285 will force the rekeying of the ssh connection. With a compatible
286 server, this can delegate the renewed credentials to a session on
287 the server. The default is “no”.
288 GSSAPITrustDns
290 Set to “yes to indicate that the DNS is trusted to securely
291 canonicalize” the name of the host being connected to. If “no,
292 the hostname entered on the” command line will be passed
293 untouched to the GSSAPI library. The default is “no”. This
294 option only applies to protocol version 2 connections using GSS‐
295 API.
296 HashKnownHosts
298 Indicates that ssh(1) should hash host names and addresses when
299 they are added to ~/.ssh/known_hosts. These hashed names may be
300 used normally by ssh(1) and sshd(8), but they do not reveal iden‐
301 tifying information should the file's contents be disclosed. The
302 default is “no”. Note that existing names and addresses in known
303 hosts files will not be converted automatically, but may be manu‐
304 ally hashed using ssh-keygen(1).
305 HostbasedAuthentication
307 Specifies whether to try rhosts based authentication with public
308 key authentication. The argument must be “yes” or “no”. The
309 default is “no”. This option applies to protocol version 2 only
310 and is similar to RhostsRSAAuthentication.
311 HostKeyAlgorithms
313 Specifies the protocol version 2 host key algorithms that the
314 client wants to use in order of preference. The default for this
315 option is: “ssh-rsa,ssh-dss”.
316 HostKeyAlias
318 Specifies an alias that should be used instead of the real host
319 name when looking up or saving the host key in the host key data‐
320 base files. This option is useful for tunneling SSH connections
321 or for multiple servers running on a single host.
322 HostName
324 Specifies the real host name to log into. This can be used to
325 specify nicknames or abbreviations for hosts. The default is the
326 name given on the command line. Numeric IP addresses are also
327 permitted (both on the command line and in HostName specifica‐
328 tions).
329 IdentitiesOnly
331 Specifies that ssh(1) should only use the authentication identity
332 files configured in the ssh_config files, even if ssh-agent(1)
333 offers more identities. The argument to this keyword must be
334 “yes” or “no”. This option is intended for situations where ssh-
335 agent offers many different identities. The default is “no”.
336 IdentityFile
338 Specifies a file from which the user's RSA or DSA authentication
339 identity is read. The default is ~/.ssh/identity for protocol
340 version 1, and ~/.ssh/id_rsa and ~/.ssh/id_dsa for protocol ver‐
341 sion 2. Additionally, any identities represented by the authen‐
342 tication agent will be used for authentication. ssh(1) will try
343 to load certificate information from the filename obtained by
344 appending -cert.pub to the path of a specified IdentityFile.
345 The file name may use the tilde syntax to refer to a user's home
347 directory or one of the following escape characters: ‘%d’ (local
348 user's home directory), ‘%u’ (local user name), ‘%l’ (local host
349 name), ‘%h’ (remote host name) or ‘%r’ (remote user name).
350 It is possible to have multiple identity files specified in con‐
352 figuration files; all these identities will be tried in sequence.
353 KbdInteractiveAuthentication
355 Specifies whether to use keyboard-interactive authentication.
356 The argument to this keyword must be “yes” or “no”. The default
357 is “yes”.
358 KbdInteractiveDevices
360 Specifies the list of methods to use in keyboard-interactive
361 authentication. Multiple method names must be comma-separated.
362 The default is to use the server specified list. The methods
363 available vary depending on what the server supports. For an
364 OpenSSH server, it may be zero or more of: “bsdauth”, “pam”, and
365 “skey”.
366 LocalCommand
368 Specifies a command to execute on the local machine after suc‐
369 cessfully connecting to the server. The command string extends
370 to the end of the line, and is executed with the user's shell.
371 The following escape character substitutions will be performed:
372 ‘%d’ (local user's home directory), ‘%h’ (remote host name), ‘%l’
373 (local host name), ‘%n’ (host name as provided on the command
374 line), ‘%p’ (remote port), ‘%r’ (remote user name) or ‘%u’ (local
375 user name).
376 The command is run synchronously and does not have access to the
378 session of the ssh(1) that spawned it. It should not be used for
379 interactive commands.
380 This directive is ignored unless PermitLocalCommand has been
382 enabled.
383 LocalForward
385 Specifies that a TCP port on the local machine be forwarded over
386 the secure channel to the specified host and port from the remote
387 machine. The first argument must be [bind_address:]port and the
388 second argument must be host:hostport. IPv6 addresses can be
389 specified by enclosing addresses in square brackets or by using
390 an alternative syntax: [bind_address/]port and host/hostport.
391 Multiple forwardings may be specified, and additional forwardings
392 can be given on the command line. Only the superuser can forward
393 privileged ports. By default, the local port is bound in accor‐
394 dance with the GatewayPorts setting. However, an explicit
395 bind_address may be used to bind the connection to a specific
396 address. The bind_address of “localhost” indicates that the lis‐
397 tening port be bound for local use only, while an empty address
398 or ‘*’ indicates that the port should be available from all
399 interfaces.
400 LogLevel
402 Gives the verbosity level that is used when logging messages from
403 ssh(1). The possible values are: QUIET, FATAL, ERROR, INFO, VER‐
404 BOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO.
405 DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify
406 higher levels of verbose output.
407 MACs Specifies the MAC (message authentication code) algorithms in
409 order of preference. The MAC algorithm is used in protocol ver‐
410 sion 2 for data integrity protection. Multiple algorithms must
411 be comma-separated. The default is:
412 hmac-md5,hmac-sha1,umac-64@openssh.com,
414 hmac-ripemd160,hmac-sha1-96,hmac-md5-96
415 NoHostAuthenticationForLocalhost
417 This option can be used if the home directory is shared across
418 machines. In this case localhost will refer to a different
419 machine on each of the machines and the user will get many warn‐
420 ings about changed host keys. However, this option disables host
421 authentication for localhost. The argument to this keyword must
422 be “yes” or “no”. The default is to check the host key for
423 localhost.
424 NumberOfPasswordPrompts
426 Specifies the number of password prompts before giving up. The
427 argument to this keyword must be an integer. The default is 3.
428 PasswordAuthentication
430 Specifies whether to use password authentication. The argument
431 to this keyword must be “yes” or “no”. The default is “yes”.
432 PermitLocalCommand
434 Allow local command execution via the LocalCommand option or
435 using the !command escape sequence in ssh(1). The argument must
436 be “yes” or “no”. The default is “no”.
437 PKCS11Provider
439 Specifies which PKCS#11 provider to use. The argument to this
440 keyword is the PKCS#11 shared libary ssh(1) should use to commu‐
441 nicate with a PKCS#11 token providing the user's private RSA key.
442 Port Specifies the port number to connect on the remote host. The
444 default is 22.
445 PreferredAuthentications
447 Specifies the order in which the client should try protocol 2
448 authentication methods. This allows a client to prefer one
449 method (e.g. keyboard-interactive) over another method (e.g.
450 password) The default for this option is:
451 “gssapi-with-mic,hostbased,publickey,keyboard-interactive,password”.
452 Protocol
454 Specifies the protocol versions ssh(1) should support in order of
455 preference. The possible values are ‘1’ and ‘2’. Multiple ver‐
456 sions must be comma-separated. When this option is set to “2,1”
457 ssh will try version 2 and fall back to version 1 if version 2 is
458 not available. The default is ‘2’.
459 ProxyCommand
461 Specifies the command to use to connect to the server. The com‐
462 mand string extends to the end of the line, and is executed with
463 the user's shell. In the command string, ‘%h’ will be substi‐
464 tuted by the host name to connect and ‘%p’ by the port. The com‐
465 mand can be basically anything, and should read from its standard
466 input and write to its standard output. It should eventually
467 connect an sshd(8) server running on some machine, or execute
468 sshd -i somewhere. Host key management will be done using the
469 HostName of the host being connected (defaulting to the name
470 typed by the user). Setting the command to “none” disables this
471 option entirely. Note that CheckHostIP is not available for con‐
472 nects with a proxy command.
473 This directive is useful in conjunction with nc(1) and its proxy
475 support. For example, the following directive would connect via
476 an HTTP proxy at 192.0.2.0:
477 ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
479 PubkeyAuthentication
481 Specifies whether to try public key authentication. The argument
482 to this keyword must be “yes” or “no”. The default is “yes”.
483 This option applies to protocol version 2 only.
484 RekeyLimit
486 Specifies the maximum amount of data that may be transmitted
487 before the session key is renegotiated. The argument is the num‐
488 ber of bytes, with an optional suffix of ‘K’, ‘M’, or ‘G’ to
489 indicate Kilobytes, Megabytes, or Gigabytes, respectively. The
490 default is between ‘1G’ and ‘4G’, depending on the cipher. This
491 option applies to protocol version 2 only.
492 RemoteForward
494 Specifies that a TCP port on the remote machine be forwarded over
495 the secure channel to the specified host and port from the local
496 machine. The first argument must be [bind_address:]port and the
497 second argument must be host:hostport. IPv6 addresses can be
498 specified by enclosing addresses in square brackets or by using
499 an alternative syntax: [bind_address/]port and host/hostport.
500 Multiple forwardings may be specified, and additional forwardings
501 can be given on the command line. Privileged ports can be for‐
502 warded only when logging in as root on the remote machine.
503 If the port argument is ‘0’, the listen port will be dynamically
505 allocated on the server and reported to the client at run time.
506 If the bind_address is not specified, the default is to only bind
508 to loopback addresses. If the bind_address is ‘*’ or an empty
509 string, then the forwarding is requested to listen on all inter‐
510 faces. Specifying a remote bind_address will only succeed if the
511 server's GatewayPorts option is enabled (see sshd_config(5)).
512 RhostsRSAAuthentication
514 Specifies whether to try rhosts based authentication with RSA
515 host authentication. The argument must be “yes” or “no”. The
516 default is “no”. This option applies to protocol version 1 only
517 and requires ssh(1) to be setuid root.
518 RSAAuthentication
520 Specifies whether to try RSA authentication. The argument to
521 this keyword must be “yes” or “no”. RSA authentication will only
522 be attempted if the identity file exists, or an authentication
523 agent is running. The default is “yes”. Note that this option
524 applies to protocol version 1 only.
525 SendEnv
527 Specifies what variables from the local environ(7) should be sent
528 to the server. Note that environment passing is only supported
529 for protocol 2. The server must also support it, and the server
530 must be configured to accept these environment variables. Refer
531 to AcceptEnv in sshd_config(5) for how to configure the server.
532 Variables are specified by name, which may contain wildcard char‐
533 acters. Multiple environment variables may be separated by
534 whitespace or spread across multiple SendEnv directives. The
535 default is not to send any environment variables.
536 See PATTERNS for more information on patterns.
538 ServerAliveCountMax
540 Sets the number of server alive messages (see below) which may be
541 sent without ssh(1) receiving any messages back from the server.
542 If this threshold is reached while server alive messages are
543 being sent, ssh will disconnect from the server, terminating the
544 session. It is important to note that the use of server alive
545 messages is very different from TCPKeepAlive (below). The server
546 alive messages are sent through the encrypted channel and there‐
547 fore will not be spoofable. The TCP keepalive option enabled by
548 TCPKeepAlive is spoofable. The server alive mechanism is valu‐
549 able when the client or server depend on knowing when a connec‐
550 tion has become inactive.
551 The default value is 3. If, for example, ServerAliveInterval
553 (see below) is set to 15 and ServerAliveCountMax is left at the
554 default, if the server becomes unresponsive, ssh will disconnect
555 after approximately 45 seconds. This option applies to protocol
556 version 2 only.
557 ServerAliveInterval
559 Sets a timeout interval in seconds after which if no data has
560 been received from the server, ssh(1) will send a message through
561 the encrypted channel to request a response from the server. The
562 default is 0, indicating that these messages will not be sent to
563 the server. This option applies to protocol version 2 only.
564 StrictHostKeyChecking
566 If this flag is set to “yes”, ssh(1) will never automatically add
567 host keys to the ~/.ssh/known_hosts file, and refuses to connect
568 to hosts whose host key has changed. This provides maximum pro‐
569 tection against trojan horse attacks, though it can be annoying
570 when the /etc/ssh/ssh_known_hosts file is poorly maintained or
571 when connections to new hosts are frequently made. This option
572 forces the user to manually add all new hosts. If this flag is
573 set to “no”, ssh will automatically add new host keys to the user
574 known hosts files. If this flag is set to “ask”, new host keys
575 will be added to the user known host files only after the user
576 has confirmed that is what they really want to do, and ssh will
577 refuse to connect to hosts whose host key has changed. The host
578 keys of known hosts will be verified automatically in all cases.
579 The argument must be “yes”, “no”, or “ask”. The default is
580 “ask”.
581 TCPKeepAlive
583 Specifies whether the system should send TCP keepalive messages
584 to the other side. If they are sent, death of the connection or
585 crash of one of the machines will be properly noticed. However,
586 this means that connections will die if the route is down tempo‐
587 rarily, and some people find it annoying.
588 The default is “yes” (to send TCP keepalive messages), and the
590 client will notice if the network goes down or the remote host
591 dies. This is important in scripts, and many users want it too.
592 To disable TCP keepalive messages, the value should be set to
594 “no”.
595 Tunnel Request tun(4) device forwarding between the client and the
597 server. The argument must be “yes”, “point-to-point” (layer 3),
598 “ethernet” (layer 2), or “no”. Specifying “yes” requests the
599 default tunnel mode, which is “point-to-point”. The default is
600 “no”.
601 TunnelDevice
603 Specifies the tun(4) devices to open on the client (local_tun)
604 and the server (remote_tun).
605 The argument must be local_tun[:remote_tun]. The devices may be
607 specified by numerical ID or the keyword “any”, which uses the
608 next available tunnel device. If remote_tun is not specified, it
609 defaults to “any”. The default is “any:any”.
610 UsePrivilegedPort
612 Specifies whether to use a privileged port for outgoing connec‐
613 tions. The argument must be “yes” or “no”. The default is “no”.
614 If set to “yes”, ssh(1) must be setuid root. Note that this
615 option must be set to “yes” for RhostsRSAAuthentication with
616 older servers.
617 User Specifies the user to log in as. This can be useful when a dif‐
619 ferent user name is used on different machines. This saves the
620 trouble of having to remember to give the user name on the com‐
621 mand line.
622 UserKnownHostsFile
624 Specifies a file to use for the user host key database instead of
625 ~/.ssh/known_hosts.
626 VerifyHostKeyDNS
628 Specifies whether to verify the remote key using DNS and SSHFP
629 resource records. If this option is set to “yes”, the client
630 will implicitly trust keys that match a secure fingerprint from
631 DNS. Insecure fingerprints will be handled as if this option was
632 set to “ask”. If this option is set to “ask”, information on
633 fingerprint match will be displayed, but the user will still need
634 to confirm new host keys according to the StrictHostKeyChecking
635 option. The argument must be “yes”, “no”, or “ask”. The default
636 is “no”. Note that this option applies to protocol version 2
637 only.
638 See also VERIFYING HOST KEYS in ssh(1).
640 VisualHostKey
642 If this flag is set to “yes”, an ASCII art representation of the
643 remote host key fingerprint is printed in addition to the hex
644 fingerprint string at login and for unknown host keys. If this
645 flag is set to “no”, no fingerprint strings are printed at login
646 and only the hex fingerprint string will be printed for unknown
647 host keys. The default is “no”.
648 XAuthLocation
650 Specifies the full pathname of the xauth(1) program. The default
651 is /usr/bin/xauth.
652
654 A pattern consists of zero or more non-whitespace characters, ‘*’ (a
655 wildcard that matches zero or more characters), or ‘?’ (a wildcard that
656 matches exactly one character). For example, to specify a set of decla‐
657 rations for any host in the “.co.uk” set of domains, the following pat‐
658 tern could be used:
659 Host *.co.uk
661 The following pattern would match any host in the 192.168.0.[0-9] network
663 range:
664 Host 192.168.0.?
666 A pattern-list is a comma-separated list of patterns. Patterns within
668 pattern-lists may be negated by preceding them with an exclamation mark
669 (‘!’). For example, to allow a key to be used from anywhere within an
670 organisation except from the “dialup” pool, the following entry (in
671 authorized_keys) could be used:
672 from="!*.dialup.example.com,*.example.com"
674
676 ~/.ssh/config
677 This is the per-user configuration file. The format of this file
678 is described above. This file is used by the SSH client.
679 Because of the potential for abuse, this file must have strict
680 permissions: read/write for the user, and not accessible by oth‐
681 ers.
682 /etc/ssh/ssh_config
684 Systemwide configuration file. This file provides defaults for
685 those values that are not specified in the user's configuration
686 file, and for those users who do not have a configuration file.
687 This file must be world-readable.
688
690 ssh(1)
691
693 OpenSSH is a derivative of the original and free ssh 1.2.12 release by
694 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
695 de Raadt and Dug Song removed many bugs, re-added newer features and cre‐
696 ated OpenSSH. Markus Friedl contributed the support for SSH protocol
697 versions 1.5 and 2.0.
698BSD June 22, 2019 BSD