1 SSH_CONFIG(5) OpenBSD Programmer's Manual SSH_CONFIG(5)
4 ssh_config - OpenSSH SSH client configuration files
11 ssh(1) obtains configuration data from the following sources in the
14 1. command-line options
15 2. user's configuration file (~/.ssh/config)
16 3. system-wide configuration file (/etc/ssh/ssh_config)
18 For each parameter, the first obtained value will be used. The
19 configuration files contain sections separated by ``Host''
20 specifications, and that section is only applied for hosts that match one
21 of the patterns given in the specification. The matched host name is the
22 one given on the command line.
24 Since the first obtained value for each parameter is used, more host-
25 specific declarations should be given near the beginning of the file, and
26 general defaults at the end.
28 The configuration file has the following format:
30 Empty lines and lines starting with `#' are comments. Otherwise a line
31 is of the format ``keyword arguments''. Configuration options may be
32 separated by whitespace or optional whitespace and exactly one `='; the
33 latter format is useful to avoid the need to quote whitespace when
34 specifying configuration options using the ssh, scp, and sftp -o option.
35 Arguments may optionally be enclosed in double quotes (") in order to
36 represent arguments containing spaces.
38 The possible keywords and their meanings are as follows (note that
39 keywords are case-insensitive and arguments are case-sensitive):
41 Host Restricts the following declarations (up to the next Host
42 keyword) to be only for those hosts that match one of the
43 patterns given after the keyword. If more than one pattern is
44 provided, they should be separated by whitespace. A single `*'
45 as a pattern can be used to provide global defaults for all
46 hosts. The host is the hostname argument given on the command
47 line (i.e. the name is not converted to a canonicalized host name
50 A pattern entry may be negated by prefixing it with an
51 exclamation mark (`!'). If a negated entry is matched, then the
52 Host entry is ignored, regardless of whether any other patterns
53 on the line match. Negated matches are therefore useful to
54 provide exceptions for wildcard matches.
56 See PATTERNS for more information on patterns.
59 Specifies which address family to use when connecting. Valid
60 arguments are ``any'', ``inet'' (use IPv4 only), or ``inet6''
64 If set to ``yes'', passphrase/password querying will be disabled.
65 This option is useful in scripts and other batch jobs where no
66 user is present to supply the password. The argument must be
67 ``yes'' or ``no''. The default is ``no''.
70 Use the specified address on the local machine as the source
71 address of the connection. Only useful on systems with more than
72 one address. Note that this option does not work if
73 UsePrivilegedPort is set to ``yes''.
75 ChallengeResponseAuthentication
76 Specifies whether to use challenge-response authentication. The
77 argument to this keyword must be ``yes'' or ``no''. The default
81 If this flag is set to ``yes'', ssh(1) will additionally check
82 the host IP address in the known_hosts file. This allows ssh to
83 detect if a host key changed due to DNS spoofing. If the option
84 is set to ``no'', the check will not be executed. The default is
87 Cipher Specifies the cipher to use for encrypting the session in
88 protocol version 1. Currently, ``blowfish'', ``3des'', and
89 ``des'' are supported. des is only supported in the ssh(1)
90 client for interoperability with legacy protocol 1
91 implementations that do not support the 3des cipher. Its use is
92 strongly discouraged due to cryptographic weaknesses. The
96 Specifies the ciphers allowed for protocol version 2 in order of
97 preference. Multiple ciphers must be comma-separated. The
98 supported ciphers are ``3des-cbc'', ``aes128-cbc'',
99 ``aes192-cbc'', ``aes256-cbc'', ``aes128-ctr'', ``aes192-ctr'',
100 ``aes256-ctr'', ``arcfour128'', ``arcfour256'', ``arcfour'',
101 ``blowfish-cbc'', and ``cast128-cbc''. The default is:
103 aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
104 aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
108 Specifies that all local, remote, and dynamic port forwardings
109 specified in the configuration files or on the command line be
110 cleared. This option is primarily useful when used from the
111 ssh(1) command line to clear port forwardings set in
112 configuration files, and is automatically set by scp(1) and
113 sftp(1). The argument must be ``yes'' or ``no''. The default is
117 Specifies whether to use compression. The argument must be
118 ``yes'' or ``no''. The default is ``no''.
121 Specifies the compression level to use if compression is enabled.
122 The argument must be an integer from 1 (fast) to 9 (slow, best).
123 The default level is 6, which is good for most applications. The
124 meaning of the values is the same as in gzip(1). Note that this
125 option applies to protocol version 1 only.
128 Specifies the number of tries (one per second) to make before
129 exiting. The argument must be an integer. This may be useful in
130 scripts if the connection sometimes fails. The default is 1.
133 Specifies the timeout (in seconds) used when connecting to the
134 SSH server, instead of using the default system TCP timeout.
135 This value is used only when the target is down or really
136 unreachable, not when it refuses the connection.
139 Enables the sharing of multiple sessions over a single network
140 connection. When set to ``yes'', ssh(1) will listen for
141 connections on a control socket specified using the ControlPath
142 argument. Additional sessions can connect to this socket using
143 the same ControlPath with ControlMaster set to ``no'' (the
144 default). These sessions will try to reuse the master instance's
145 network connection rather than initiating new ones, but will fall
146 back to connecting normally if the control socket does not exist,
149 Setting this to ``ask'' will cause ssh to listen for control
150 connections, but require confirmation using the SSH_ASKPASS
151 program before they are accepted (see ssh-add(1) for details).
152 If the ControlPath cannot be opened, ssh will continue without
153 connecting to a master instance.
155 X11 and ssh-agent(1) forwarding is supported over these
156 multiplexed connections, however the display and agent forwarded
157 will be the one belonging to the master connection i.e. it is not
158 possible to forward multiple displays or agents.
160 Two additional options allow for opportunistic multiplexing: try
161 to use a master connection but fall back to creating a new one if
162 one does not already exist. These options are: ``auto'' and
163 ``autoask''. The latter requires confirmation like the ``ask''
167 Specify the path to the control socket used for connection
168 sharing as described in the ControlMaster section above or the
169 string ``none'' to disable connection sharing. In the path, `%L'
170 will be substituted by the first component of the local host
171 name, `%l' will be substituted by the local host name (including
172 any domain name), `%h' will be substituted by the target host
173 name, `%n' will be substituted by the original target host name
174 specified on the command line, `%p' the port, `%r' by the remote
175 login username, and `%u' by the username of the user running
176 ssh(1). It is recommended that any ControlPath used for
177 opportunistic connection sharing include at least %h, %p, and %r.
178 This ensures that shared connections are uniquely identified.
181 When used in conjunction with ControlMaster, specifies that the
182 master connection should remain open in the background (waiting
183 for future client connections) after the initial client
184 connection has been closed. If set to ``no'', then the master
185 connection will not be placed into the background, and will close
186 as soon as the initial client connection is closed. If set to
187 ``yes'', then the master connection will remain in the background
188 indefinitely (until killed or closed via a mechanism such as the
189 ssh(1) ``-O exit'' option). If set to a time in seconds, or a
190 time in any of the formats documented in sshd_config(5), then the
191 backgrounded master connection will automatically terminate after
192 it has remained idle (with no client connections) for the
196 Specifies that a TCP port on the local machine be forwarded over
197 the secure channel, and the application protocol is then used to
198 determine where to connect to from the remote machine.
200 The argument must be [bind_address:]port. IPv6 addresses can be
201 specified by enclosing addresses in square brackets. By default,
202 the local port is bound in accordance with the GatewayPorts
203 setting. However, an explicit bind_address may be used to bind
204 the connection to a specific address. The bind_address of
205 ``localhost'' indicates that the listening port be bound for
206 local use only, while an empty address or `*' indicates that the
207 port should be available from all interfaces.
209 Currently the SOCKS4 and SOCKS5 protocols are supported, and
210 ssh(1) will act as a SOCKS server. Multiple forwardings may be
211 specified, and additional forwardings can be given on the command
212 line. Only the superuser can forward privileged ports.
215 Setting this option to ``yes'' in the global client configuration
216 file /etc/ssh/ssh_config enables the use of the helper program
217 ssh-keysign(8) during HostbasedAuthentication. The argument must
218 be ``yes'' or ``no''. The default is ``no''. This option should
219 be placed in the non-hostspecific section. See ssh-keysign(8)
220 for more information.
223 Sets the escape character (default: `~'). The escape character
224 can also be set on the command line. The argument should be a
225 single character, `^' followed by a letter, or ``none'' to
226 disable the escape character entirely (making the connection
227 transparent for binary data).
230 Specifies whether ssh(1) should terminate the connection if it
231 cannot set up all requested dynamic, tunnel, local, and remote
232 port forwardings. The argument must be ``yes'' or ``no''. The
236 Specifies whether the connection to the authentication agent (if
237 any) will be forwarded to the remote machine. The argument must
238 be ``yes'' or ``no''. The default is ``no''.
240 Agent forwarding should be enabled with caution. Users with the
241 ability to bypass file permissions on the remote host (for the
242 agent's Unix-domain socket) can access the local agent through
243 the forwarded connection. An attacker cannot obtain key material
244 from the agent, however they can perform operations on the keys
245 that enable them to authenticate using the identities loaded into
249 Specifies whether X11 connections will be automatically
250 redirected over the secure channel and DISPLAY set. The argument
251 must be ``yes'' or ``no''. The default is ``no''.
253 X11 forwarding should be enabled with caution. Users with the
254 ability to bypass file permissions on the remote host (for the
255 user's X11 authorization database) can access the local X11
256 display through the forwarded connection. An attacker may then
257 be able to perform activities such as keystroke monitoring if the
258 ForwardX11Trusted option is also enabled.
261 Specify a timeout for untrusted X11 forwarding using the format
262 described in the TIME FORMATS section of sshd_config(5). X11
263 connections received by ssh(1) after this time will be refused.
264 The default is to disable untrusted X11 forwarding after twenty
268 If this option is set to ``yes'', remote X11 clients will have
269 full access to the original X11 display.
271 If this option is set to ``no'', remote X11 clients will be
272 considered untrusted and prevented from stealing or tampering
273 with data belonging to trusted X11 clients. Furthermore, the
274 xauth(1) token used for the session will be set to expire after
275 20 minutes. Remote clients will be refused access after this
278 The default is ``no''.
280 See the X11 SECURITY extension specification for full details on
281 the restrictions imposed on untrusted clients.
284 Specifies whether remote hosts are allowed to connect to local
285 forwarded ports. By default, ssh(1) binds local port forwardings
286 to the loopback address. This prevents other remote hosts from
287 connecting to forwarded ports. GatewayPorts can be used to
288 specify that ssh should bind local port forwardings to the
289 wildcard address, thus allowing remote hosts to connect to
290 forwarded ports. The argument must be ``yes'' or ``no''. The
294 Specifies one or more files to use for the global host key
295 database, separated by whitespace. The default is
296 /etc/ssh/ssh_known_hosts, /etc/ssh/ssh_known_hosts2.
299 Specifies whether user authentication based on GSSAPI is allowed.
300 The default is ``no''. Note that this option applies to protocol
303 GSSAPIDelegateCredentials
304 Forward (delegate) credentials to the server. The default is
305 ``no''. Note that this option applies to protocol version 2
309 Indicates that ssh(1) should hash host names and addresses when
310 they are added to ~/.ssh/known_hosts. These hashed names may be
311 used normally by ssh(1) and sshd(8), but they do not reveal
312 identifying information should the file's contents be disclosed.
313 The default is ``no''. Note that existing names and addresses in
314 known hosts files will not be converted automatically, but may be
315 manually hashed using ssh-keygen(1).
317 HostbasedAuthentication
318 Specifies whether to try rhosts based authentication with public
319 key authentication. The argument must be ``yes'' or ``no''. The
320 default is ``no''. This option applies to protocol version 2
321 only and is similar to RhostsRSAAuthentication.
324 Specifies the protocol version 2 host key algorithms that the
325 client wants to use in order of preference. The default for this
328 ecdsa-sha2-nistp256-cert-v01@openssh.com,
329 ecdsa-sha2-nistp384-cert-v01@openssh.com,
330 ecdsa-sha2-nistp521-cert-v01@openssh.com,
331 ssh-rsa-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,
332 ssh-rsa-cert-v00@openssh.com,ssh-dss-cert-v00@openssh.com,
333 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
336 If hostkeys are known for the destination host then this default
337 is modified to prefer their algorithms.
340 Specifies an alias that should be used instead of the real host
341 name when looking up or saving the host key in the host key
342 database files. This option is useful for tunneling SSH
343 connections or for multiple servers running on a single host.
346 Specifies the real host name to log into. This can be used to
347 specify nicknames or abbreviations for hosts. If the hostname
348 contains the character sequence `%h', then this will be replaced
349 with the host name specified on the command line (this is useful
350 for manipulating unqualified names). The default is the name
351 given on the command line. Numeric IP addresses are also
352 permitted (both on the command line and in HostName
356 Specifies that ssh(1) should only use the authentication identity
357 files configured in the ssh_config files, even if ssh-agent(1)
358 offers more identities. The argument to this keyword must be
359 ``yes'' or ``no''. This option is intended for situations where
360 ssh-agent offers many different identities. The default is
364 Specifies a file from which the user's DSA, ECDSA or RSA
365 authentication identity is read. The default is ~/.ssh/identity
366 for protocol version 1, and ~/.ssh/id_dsa, ~/.ssh/id_ecdsa and
367 ~/.ssh/id_rsa for protocol version 2. Additionally, any
368 identities represented by the authentication agent will be used
369 for authentication. ssh(1) will try to load certificate
370 information from the filename obtained by appending -cert.pub to
371 the path of a specified IdentityFile.
373 The file name may use the tilde syntax to refer to a user's home
374 directory or one of the following escape characters: `%d' (local
375 user's home directory), `%u' (local user name), `%l' (local host
376 name), `%h' (remote host name) or `%r' (remote user name).
378 It is possible to have multiple identity files specified in
379 configuration files; all these identities will be tried in
380 sequence. Multiple IdentityFile directives will add to the list
381 of identities tried (this behaviour differs from that of other
382 configuration directives).
384 IPQoS Specifies the IPv4 type-of-service or DSCP class for connections.
385 Accepted values are ``af11'', ``af12'', ``af13'', ``af21'',
386 ``af22'', ``af23'', ``af31'', ``af32'', ``af33'', ``af41'',
387 ``af42'', ``af43'', ``cs0'', ``cs1'', ``cs2'', ``cs3'', ``cs4'',
388 ``cs5'', ``cs6'', ``cs7'', ``ef'', ``lowdelay'', ``throughput'',
389 ``reliability'', or a numeric value. This option may take one or
390 two arguments, separated by whitespace. If one argument is
391 specified, it is used as the packet class unconditionally. If
392 two values are specified, the first is automatically selected for
393 interactive sessions and the second for non-interactive sessions.
394 The default is ``lowdelay'' for interactive sessions and
395 ``throughput'' for non-interactive sessions.
397 KbdInteractiveAuthentication
398 Specifies whether to use keyboard-interactive authentication.
399 The argument to this keyword must be ``yes'' or ``no''. The
402 KbdInteractiveDevices
403 Specifies the list of methods to use in keyboard-interactive
404 authentication. Multiple method names must be comma-separated.
405 The default is to use the server specified list. The methods
406 available vary depending on what the server supports. For an
407 OpenSSH server, it may be zero or more of: ``bsdauth'', ``pam'',
411 Specifies the available KEX (Key Exchange) algorithms. Multiple
412 algorithms must be comma-separated. The default is:
414 ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,
415 diffie-hellman-group-exchange-sha256,
416 diffie-hellman-group-exchange-sha1,
417 diffie-hellman-group14-sha1,
418 diffie-hellman-group1-sha1
421 Specifies a command to execute on the local machine after
422 successfully connecting to the server. The command string
423 extends to the end of the line, and is executed with the user's
424 shell. The following escape character substitutions will be
425 performed: `%d' (local user's home directory), `%h' (remote host
426 name), `%l' (local host name), `%n' (host name as provided on the
427 command line), `%p' (remote port), `%r' (remote user name) or
428 `%u' (local user name).
430 The command is run synchronously and does not have access to the
431 session of the ssh(1) that spawned it. It should not be used for
432 interactive commands.
434 This directive is ignored unless PermitLocalCommand has been
438 Specifies that a TCP port on the local machine be forwarded over
439 the secure channel to the specified host and port from the remote
440 machine. The first argument must be [bind_address:]port and the
441 second argument must be host:hostport. IPv6 addresses can be
442 specified by enclosing addresses in square brackets. Multiple
443 forwardings may be specified, and additional forwardings can be
444 given on the command line. Only the superuser can forward
445 privileged ports. By default, the local port is bound in
446 accordance with the GatewayPorts setting. However, an explicit
447 bind_address may be used to bind the connection to a specific
448 address. The bind_address of ``localhost'' indicates that the
449 listening port be bound for local use only, while an empty
450 address or `*' indicates that the port should be available from
454 Gives the verbosity level that is used when logging messages from
455 ssh(1). The possible values are: QUIET, FATAL, ERROR, INFO,
456 VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO.
457 DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify
458 higher levels of verbose output.
460 MACs Specifies the MAC (message authentication code) algorithms in
461 order of preference. The MAC algorithm is used in protocol
462 version 2 for data integrity protection. Multiple algorithms
463 must be comma-separated. The default is:
465 hmac-md5,hmac-sha1,umac-64@openssh.com,
466 hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,
467 hmac-sha1-96,hmac-md5-96
469 NoHostAuthenticationForLocalhost
470 This option can be used if the home directory is shared across
471 machines. In this case localhost will refer to a different
472 machine on each of the machines and the user will get many
473 warnings about changed host keys. However, this option disables
474 host authentication for localhost. The argument to this keyword
475 must be ``yes'' or ``no''. The default is to check the host key
478 NumberOfPasswordPrompts
479 Specifies the number of password prompts before giving up. The
480 argument to this keyword must be an integer. The default is 3.
482 PasswordAuthentication
483 Specifies whether to use password authentication. The argument
484 to this keyword must be ``yes'' or ``no''. The default is
488 Allow local command execution via the LocalCommand option or
489 using the !command escape sequence in ssh(1). The argument must
490 be ``yes'' or ``no''. The default is ``no''.
493 Specifies which PKCS#11 provider to use. The argument to this
494 keyword is the PKCS#11 shared library ssh(1) should use to
495 communicate with a PKCS#11 token providing the user's private RSA
498 Port Specifies the port number to connect on the remote host. The
501 PreferredAuthentications
502 Specifies the order in which the client should try protocol 2
503 authentication methods. This allows a client to prefer one
504 method (e.g. keyboard-interactive) over another method (e.g.
505 password). The default is:
507 gssapi-with-mic,hostbased,publickey,
508 keyboard-interactive,password
511 Specifies the protocol versions ssh(1) should support in order of
512 preference. The possible values are `1' and `2'. Multiple
513 versions must be comma-separated. When this option is set to
514 ``2,1'' ssh will try version 2 and fall back to version 1 if
515 version 2 is not available. The default is `2'.
518 Specifies the command to use to connect to the server. The
519 command string extends to the end of the line, and is executed
520 with the user's shell. In the command string, any occurrence of
521 `%h' will be substituted by the host name to connect, `%p' by the
522 port, and `%r' by the remote user name. The command can be
523 basically anything, and should read from its standard input and
524 write to its standard output. It should eventually connect an
525 sshd(8) server running on some machine, or execute sshd -i
526 somewhere. Host key management will be done using the HostName
527 of the host being connected (defaulting to the name typed by the
528 user). Setting the command to ``none'' disables this option
529 entirely. Note that CheckHostIP is not available for connects
530 with a proxy command.
532 This directive is useful in conjunction with nc(1) and its proxy
533 support. For example, the following directive would connect via
534 an HTTP proxy at 192.0.2.0:
536 ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
539 Specifies whether to try public key authentication. The argument
540 to this keyword must be ``yes'' or ``no''. The default is
541 ``yes''. This option applies to protocol version 2 only.
544 Specifies the maximum amount of data that may be transmitted
545 before the session key is renegotiated. The argument is the
546 number of bytes, with an optional suffix of `K', `M', or `G' to
547 indicate Kilobytes, Megabytes, or Gigabytes, respectively. The
548 default is between `1G' and `4G', depending on the cipher. This
549 option applies to protocol version 2 only.
552 Specifies that a TCP port on the remote machine be forwarded over
553 the secure channel to the specified host and port from the local
554 machine. The first argument must be [bind_address:]port and the
555 second argument must be host:hostport. IPv6 addresses can be
556 specified by enclosing addresses in square brackets. Multiple
557 forwardings may be specified, and additional forwardings can be
558 given on the command line. Privileged ports can be forwarded
559 only when logging in as root on the remote machine.
561 If the port argument is `0', the listen port will be dynamically
562 allocated on the server and reported to the client at run time.
564 If the bind_address is not specified, the default is to only bind
565 to loopback addresses. If the bind_address is `*' or an empty
566 string, then the forwarding is requested to listen on all
567 interfaces. Specifying a remote bind_address will only succeed
568 if the server's GatewayPorts option is enabled (see
572 Specifies whether to request a pseudo-tty for the session. The
573 argument may be one of: ``no'' (never request a TTY), ``yes''
574 (always request a TTY when standard input is a TTY), ``force''
575 (always request a TTY) or ``auto'' (request a TTY when opening a
576 login session). This option mirrors the -t and -T flags for
579 RhostsRSAAuthentication
580 Specifies whether to try rhosts based authentication with RSA
581 host authentication. The argument must be ``yes'' or ``no''.
582 The default is ``no''. This option applies to protocol version 1
583 only and requires ssh(1) to be setuid root.
586 Specifies whether to try RSA authentication. The argument to
587 this keyword must be ``yes'' or ``no''. RSA authentication will
588 only be attempted if the identity file exists, or an
589 authentication agent is running. The default is ``yes''. Note
590 that this option applies to protocol version 1 only.
593 Specifies what variables from the local environ(7) should be sent
594 to the server. Note that environment passing is only supported
595 for protocol 2. The server must also support it, and the server
596 must be configured to accept these environment variables. Refer
597 to AcceptEnv in sshd_config(5) for how to configure the server.
598 Variables are specified by name, which may contain wildcard
599 characters. Multiple environment variables may be separated by
600 whitespace or spread across multiple SendEnv directives. The
601 default is not to send any environment variables.
603 See PATTERNS for more information on patterns.
606 Sets the number of server alive messages (see below) which may be
607 sent without ssh(1) receiving any messages back from the server.
608 If this threshold is reached while server alive messages are
609 being sent, ssh will disconnect from the server, terminating the
610 session. It is important to note that the use of server alive
611 messages is very different from TCPKeepAlive (below). The server
612 alive messages are sent through the encrypted channel and
613 therefore will not be spoofable. The TCP keepalive option
614 enabled by TCPKeepAlive is spoofable. The server alive mechanism
615 is valuable when the client or server depend on knowing when a
616 connection has become inactive.
618 The default value is 3. If, for example, ServerAliveInterval
619 (see below) is set to 15 and ServerAliveCountMax is left at the
620 default, if the server becomes unresponsive, ssh will disconnect
621 after approximately 45 seconds. This option applies to protocol
625 Sets a timeout interval in seconds after which if no data has
626 been received from the server, ssh(1) will send a message through
627 the encrypted channel to request a response from the server. The
628 default is 0, indicating that these messages will not be sent to
629 the server. This option applies to protocol version 2 only.
631 StrictHostKeyChecking
632 If this flag is set to ``yes'', ssh(1) will never automatically
633 add host keys to the ~/.ssh/known_hosts file, and refuses to
634 connect to hosts whose host key has changed. This provides
635 maximum protection against trojan horse attacks, though it can be
636 annoying when the /etc/ssh/ssh_known_hosts file is poorly
637 maintained or when connections to new hosts are frequently made.
638 This option forces the user to manually add all new hosts. If
639 this flag is set to ``no'', ssh will automatically add new host
640 keys to the user known hosts files. If this flag is set to
641 ``ask'', new host keys will be added to the user known host files
642 only after the user has confirmed that is what they really want
643 to do, and ssh will refuse to connect to hosts whose host key has
644 changed. The host keys of known hosts will be verified
645 automatically in all cases. The argument must be ``yes'',
646 ``no'', or ``ask''. The default is ``ask''.
649 Specifies whether the system should send TCP keepalive messages
650 to the other side. If they are sent, death of the connection or
651 crash of one of the machines will be properly noticed. However,
652 this means that connections will die if the route is down
653 temporarily, and some people find it annoying.
655 The default is ``yes'' (to send TCP keepalive messages), and the
656 client will notice if the network goes down or the remote host
657 dies. This is important in scripts, and many users want it too.
659 To disable TCP keepalive messages, the value should be set to
662 Tunnel Request tun(4) device forwarding between the client and the
663 server. The argument must be ``yes'', ``point-to-point'' (layer
664 3), ``ethernet'' (layer 2), or ``no''. Specifying ``yes''
665 requests the default tunnel mode, which is ``point-to-point''.
666 The default is ``no''.
669 Specifies the tun(4) devices to open on the client (local_tun)
670 and the server (remote_tun).
672 The argument must be local_tun[:remote_tun]. The devices may be
673 specified by numerical ID or the keyword ``any'', which uses the
674 next available tunnel device. If remote_tun is not specified, it
675 defaults to ``any''. The default is ``any:any''.
678 Specifies whether to use a privileged port for outgoing
679 connections. The argument must be ``yes'' or ``no''. The
680 default is ``no''. If set to ``yes'', ssh(1) must be setuid
681 root. Note that this option must be set to ``yes'' for
682 RhostsRSAAuthentication with older servers.
684 User Specifies the user to log in as. This can be useful when a
685 different user name is used on different machines. This saves
686 the trouble of having to remember to give the user name on the
690 Specifies one or more files to use for the user host key
691 database, separated by whitespace. The default is
692 ~/.ssh/known_hosts, ~/.ssh/known_hosts2.
695 Specifies whether to verify the remote key using DNS and SSHFP
696 resource records. If this option is set to ``yes'', the client
697 will implicitly trust keys that match a secure fingerprint from
698 DNS. Insecure fingerprints will be handled as if this option was
699 set to ``ask''. If this option is set to ``ask'', information on
700 fingerprint match will be displayed, but the user will still need
701 to confirm new host keys according to the StrictHostKeyChecking
702 option. The argument must be ``yes'', ``no'', or ``ask''. The
703 default is ``no''. Note that this option applies to protocol
706 See also VERIFYING HOST KEYS in ssh(1).
709 If this flag is set to ``yes'', an ASCII art representation of
710 the remote host key fingerprint is printed in addition to the hex
711 fingerprint string at login and for unknown host keys. If this
712 flag is set to ``no'', no fingerprint strings are printed at
713 login and only the hex fingerprint string will be printed for
714 unknown host keys. The default is ``no''.
717 Specifies the full pathname of the xauth(1) program. The default
718 is /usr/X11R6/bin/xauth.
721 A pattern consists of zero or more non-whitespace characters, `*' (a
722 wildcard that matches zero or more characters), or `?' (a wildcard that
723 matches exactly one character). For example, to specify a set of
724 declarations for any host in the ``.co.uk'' set of domains, the following
725 pattern could be used:
729 The following pattern would match any host in the 192.168.0.[0-9] network
734 A pattern-list is a comma-separated list of patterns. Patterns within
735 pattern-lists may be negated by preceding them with an exclamation mark
736 (`!'). For example, to allow a key to be used from anywhere within an
737 organisation except from the ``dialup'' pool, the following entry (in
738 authorized_keys) could be used:
740 from="!*.dialup.example.com,*.example.com"
744 This is the per-user configuration file. The format of this file
745 is described above. This file is used by the SSH client.
746 Because of the potential for abuse, this file must have strict
747 permissions: read/write for the user, and not accessible by
751 Systemwide configuration file. This file provides defaults for
752 those values that are not specified in the user's configuration
753 file, and for those users who do not have a configuration file.
754 This file must be world-readable.
760 OpenSSH is a derivative of the original and free ssh 1.2.12 release by
761 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
762 de Raadt and Dug Song removed many bugs, re-added newer features and
763 created OpenSSH. Markus Friedl contributed the support for SSH protocol
764 versions 1.5 and 2.0.
766 OpenBSD 5.2 June 29, 2012 OpenBSD 5.2
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