3 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 .\" All rights reserved
7 .\" As far as I am concerned, the code I have written for this software
8 .\" can be used freely for any purpose. Any derived versions of this
9 .\" software must be clearly marked as such, and if the derived work is
10 .\" incompatible with the protocol description in the RFC file, it must be
11 .\" called by a name other than "ssh" or "Secure Shell".
13 .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
14 .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
15 .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
17 .\" Redistribution and use in source and binary forms, with or without
18 .\" modification, are permitted provided that the following conditions
20 .\" 1. Redistributions of source code must retain the above copyright
21 .\" notice, this list of conditions and the following disclaimer.
22 .\" 2. Redistributions in binary form must reproduce the above copyright
23 .\" notice, this list of conditions and the following disclaimer in the
24 .\" documentation and/or other materials provided with the distribution.
26 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29 .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 .\" $OpenBSD: ssh_config.5,v 1.138 2010/08/04 05:37:01 djm Exp $
38 .Dd $Mdocdate: August 4 2010 $
43 .Nd OpenSSH SSH client configuration files
46 .Nm /etc/ssh/ssh_config
49 obtains configuration data from the following sources in
52 .Bl -enum -offset indent -compact
56 user's configuration file
59 system-wide configuration file
60 .Pq Pa /etc/ssh/ssh_config
63 For each parameter, the first obtained value
65 The configuration files contain sections separated by
67 specifications, and that section is only applied for hosts that
68 match one of the patterns given in the specification.
69 The matched host name is the one given on the command line.
71 Since the first obtained value for each parameter is used, more
72 host-specific declarations should be given near the beginning of the
73 file, and general defaults at the end.
75 The configuration file has the following format:
77 Empty lines and lines starting with
80 Otherwise a line is of the format
81 .Dq keyword arguments .
82 Configuration options may be separated by whitespace or
83 optional whitespace and exactly one
85 the latter format is useful to avoid the need to quote whitespace
86 when specifying configuration options using the
93 Arguments may optionally be enclosed in double quotes
95 in order to represent arguments containing spaces.
98 keywords and their meanings are as follows (note that
99 keywords are case-insensitive and arguments are case-sensitive):
102 Restricts the following declarations (up to the next
104 keyword) to be only for those hosts that match one of the patterns
105 given after the keyword.
106 If more than one pattern is provided, they should be separated by whitespace.
109 as a pattern can be used to provide global
110 defaults for all hosts.
113 argument given on the command line (i.e. the name is not converted to
114 a canonicalized host name before matching).
118 for more information on patterns.
120 Specifies which address family to use when connecting.
130 passphrase/password querying will be disabled.
131 This option is useful in scripts and other batch jobs where no user
132 is present to supply the password.
140 Use the specified address on the local machine as the source address of
142 Only useful on systems with more than one address.
143 Note that this option does not work if
144 .Cm UsePrivilegedPort
147 .It Cm ChallengeResponseAuthentication
148 Specifies whether to use challenge-response authentication.
149 The argument to this keyword must be
156 If this flag is set to
159 will additionally check the host IP address in the
162 This allows ssh to detect if a host key changed due to DNS spoofing.
163 If the option is set to
165 the check will not be executed.
169 Specifies the cipher to use for encrypting the session
170 in protocol version 1.
178 is only supported in the
180 client for interoperability with legacy protocol 1 implementations
181 that do not support the
184 Its use is strongly discouraged due to cryptographic weaknesses.
188 Specifies the ciphers allowed for protocol version 2
189 in order of preference.
190 Multiple ciphers must be comma-separated.
191 The supported ciphers are
206 .Bd -literal -offset 3n
207 aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
208 aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
211 .It Cm ClearAllForwardings
212 Specifies that all local, remote, and dynamic port forwardings
213 specified in the configuration files or on the command line be
215 This option is primarily useful when used from the
217 command line to clear port forwardings set in
218 configuration files, and is automatically set by
229 Specifies whether to use compression.
236 .It Cm CompressionLevel
237 Specifies the compression level to use if compression is enabled.
238 The argument must be an integer from 1 (fast) to 9 (slow, best).
239 The default level is 6, which is good for most applications.
240 The meaning of the values is the same as in
242 Note that this option applies to protocol version 1 only.
243 .It Cm ConnectionAttempts
244 Specifies the number of tries (one per second) to make before exiting.
245 The argument must be an integer.
246 This may be useful in scripts if the connection sometimes fails.
248 .It Cm ConnectTimeout
249 Specifies the timeout (in seconds) used when connecting to the
250 SSH server, instead of using the default system TCP timeout.
251 This value is used only when the target is down or really unreachable,
252 not when it refuses the connection.
254 Enables the sharing of multiple sessions over a single network connection.
258 will listen for connections on a control socket specified using the
261 Additional sessions can connect to this socket using the same
268 These sessions will try to reuse the master instance's network connection
269 rather than initiating new ones, but will fall back to connecting normally
270 if the control socket does not exist, or is not listening.
275 to listen for control connections, but require confirmation using the
277 program before they are accepted (see
283 ssh will continue without connecting to a master instance.
287 forwarding is supported over these multiplexed connections, however the
288 display and agent forwarded will be the one belonging to the master
289 connection i.e. it is not possible to forward multiple displays or agents.
291 Two additional options allow for opportunistic multiplexing: try to use a
292 master connection but fall back to creating a new one if one does not already
298 The latter requires confirmation like the
302 Specify the path to the control socket used for connection sharing as described
305 section above or the string
307 to disable connection sharing.
310 will be substituted by the local host name,
312 will be substituted by the target host name,
316 by the remote login username.
317 It is recommended that any
319 used for opportunistic connection sharing include
320 at least %h, %p, and %r.
321 This ensures that shared connections are uniquely identified.
322 .It Cm ControlPersist
323 When used in conjunction with
325 specifies that the master connection should remain open
326 in the background (waiting for future client connections)
327 after the initial client connection has been closed.
330 then the master connection will not be placed into the background,
331 and will close as soon as the initial client connection is closed.
334 then the master connection will remain in the background indefinitely
335 (until killed or closed via a mechanism such as the
339 If set to a time in seconds, or a time in any of the formats documented in
341 then the backgrounded master connection will automatically terminate
342 after it has remained idle (with no client connections) for the
344 .It Cm DynamicForward
345 Specifies that a TCP port on the local machine be forwarded
346 over the secure channel, and the application
347 protocol is then used to determine where to connect to from the
352 .Oo Ar bind_address : Oc Ar port .
354 IPv6 addresses can be specified by enclosing addresses in square brackets.
355 By default, the local port is bound in accordance with the
360 may be used to bind the connection to a specific address.
365 indicates that the listening port be bound for local use only, while an
368 indicates that the port should be available from all interfaces.
370 Currently the SOCKS4 and SOCKS5 protocols are supported, and
372 will act as a SOCKS server.
373 Multiple forwardings may be specified, and
374 additional forwardings can be given on the command line.
375 Only the superuser can forward privileged ports.
376 .It Cm EnableSSHKeysign
377 Setting this option to
379 in the global client configuration file
380 .Pa /etc/ssh/ssh_config
381 enables the use of the helper program
384 .Cm HostbasedAuthentication .
391 This option should be placed in the non-hostspecific section.
394 for more information.
396 Sets the escape character (default:
398 The escape character can also
399 be set on the command line.
400 The argument should be a single character,
402 followed by a letter, or
404 to disable the escape
405 character entirely (making the connection transparent for binary
407 .It Cm ExitOnForwardFailure
410 should terminate the connection if it cannot set up all requested
411 dynamic, tunnel, local, and remote port forwardings.
419 Specifies whether the connection to the authentication agent (if any)
420 will be forwarded to the remote machine.
428 Agent forwarding should be enabled with caution.
429 Users with the ability to bypass file permissions on the remote host
430 (for the agent's Unix-domain socket)
431 can access the local agent through the forwarded connection.
432 An attacker cannot obtain key material from the agent,
433 however they can perform operations on the keys that enable them to
434 authenticate using the identities loaded into the agent.
436 Specifies whether X11 connections will be automatically redirected
437 over the secure channel and
447 X11 forwarding should be enabled with caution.
448 Users with the ability to bypass file permissions on the remote host
449 (for the user's X11 authorization database)
450 can access the local X11 display through the forwarded connection.
451 An attacker may then be able to perform activities such as keystroke monitoring
453 .Cm ForwardX11Trusted
454 option is also enabled.
455 .It Cm ForwardX11Timeout
456 Specify a timeout for untrusted X11 forwarding
457 using the format described in the
461 X11 connections received by
463 after this time will be refused.
464 The default is to disable untrusted X11 forwarding after twenty minutes has
466 .It Cm ForwardX11Trusted
467 If this option is set to
469 remote X11 clients will have full access to the original X11 display.
471 If this option is set to
473 remote X11 clients will be considered untrusted and prevented
474 from stealing or tampering with data belonging to trusted X11
478 token used for the session will be set to expire after 20 minutes.
479 Remote clients will be refused access after this time.
484 See the X11 SECURITY extension specification for full details on
485 the restrictions imposed on untrusted clients.
487 Specifies whether remote hosts are allowed to connect to local
491 binds local port forwardings to the loopback address.
492 This prevents other remote hosts from connecting to forwarded ports.
494 can be used to specify that ssh
495 should bind local port forwardings to the wildcard address,
496 thus allowing remote hosts to connect to forwarded ports.
503 .It Cm GlobalKnownHostsFile
504 Specifies a file to use for the global
505 host key database instead of
506 .Pa /etc/ssh/ssh_known_hosts .
507 .It Cm GSSAPIAuthentication
508 Specifies whether user authentication based on GSSAPI is allowed.
511 Note that this option applies to protocol version 2 only.
512 .It Cm GSSAPIDelegateCredentials
513 Forward (delegate) credentials to the server.
516 Note that this option applies to protocol version 2 only.
517 .It Cm HashKnownHosts
520 should hash host names and addresses when they are added to
521 .Pa ~/.ssh/known_hosts .
522 These hashed names may be used normally by
526 but they do not reveal identifying information should the file's contents
530 Note that existing names and addresses in known hosts files
531 will not be converted automatically,
532 but may be manually hashed using
534 .It Cm HostbasedAuthentication
535 Specifies whether to try rhosts based authentication with public key
543 This option applies to protocol version 2 only and
545 .Cm RhostsRSAAuthentication .
546 .It Cm HostKeyAlgorithms
547 Specifies the protocol version 2 host key algorithms
548 that the client wants to use in order of preference.
549 The default for this option is:
550 .Dq ssh-rsa,ssh-dss .
552 Specifies an alias that should be used instead of the
553 real host name when looking up or saving the host key
554 in the host key database files.
555 This option is useful for tunneling SSH connections
556 or for multiple servers running on a single host.
558 Specifies the real host name to log into.
559 This can be used to specify nicknames or abbreviations for hosts.
560 If the hostname contains the character sequence
562 then this will be replaced with the host name specified on the commandline
563 (this is useful for manipulating unqualified names).
564 The default is the name given on the command line.
565 Numeric IP addresses are also permitted (both on the command line and in
568 .It Cm IdentitiesOnly
571 should only use the authentication identity files configured in the
576 offers more identities.
577 The argument to this keyword must be
581 This option is intended for situations where ssh-agent
582 offers many different identities.
586 Specifies a file from which the user's RSA or DSA authentication identity
590 for protocol version 1, and
594 for protocol version 2.
595 Additionally, any identities represented by the authentication agent
596 will be used for authentication.
598 will try to load certificate information from the filename obtained by
601 to the path of a specified
604 The file name may use the tilde
605 syntax to refer to a user's home directory or one of the following
608 (local user's home directory),
614 (remote host name) or
618 It is possible to have
619 multiple identity files specified in configuration files; all these
620 identities will be tried in sequence.
621 .It Cm KbdInteractiveAuthentication
622 Specifies whether to use keyboard-interactive authentication.
623 The argument to this keyword must be
629 .It Cm KbdInteractiveDevices
630 Specifies the list of methods to use in keyboard-interactive authentication.
631 Multiple method names must be comma-separated.
632 The default is to use the server specified list.
633 The methods available vary depending on what the server supports.
634 For an OpenSSH server,
635 it may be zero or more of:
641 Specifies a command to execute on the local machine after successfully
642 connecting to the server.
643 The command string extends to the end of the line, and is executed with
645 The following escape character substitutions will be performed:
647 (local user's home directory),
653 (host name as provided on the command line),
657 (remote user name) or
661 The command is run synchronously and does not have access to the
665 It should not be used for interactive commands.
667 This directive is ignored unless
668 .Cm PermitLocalCommand
671 Specifies that a TCP port on the local machine be forwarded over
672 the secure channel to the specified host and port from the remote machine.
673 The first argument must be
675 .Oo Ar bind_address : Oc Ar port
677 and the second argument must be
678 .Ar host : Ns Ar hostport .
679 IPv6 addresses can be specified by enclosing addresses in square brackets.
680 Multiple forwardings may be specified, and additional forwardings can be
681 given on the command line.
682 Only the superuser can forward privileged ports.
683 By default, the local port is bound in accordance with the
688 may be used to bind the connection to a specific address.
693 indicates that the listening port be bound for local use only, while an
696 indicates that the port should be available from all interfaces.
698 Gives the verbosity level that is used when logging messages from
700 The possible values are:
701 QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
703 DEBUG and DEBUG1 are equivalent.
704 DEBUG2 and DEBUG3 each specify higher levels of verbose output.
706 Specifies the MAC (message authentication code) algorithms
707 in order of preference.
708 The MAC algorithm is used in protocol version 2
709 for data integrity protection.
710 Multiple algorithms must be comma-separated.
712 .Bd -literal -offset indent
713 hmac-md5,hmac-sha1,umac-64@openssh.com,
714 hmac-ripemd160,hmac-sha1-96,hmac-md5-96
716 .It Cm NoHostAuthenticationForLocalhost
717 This option can be used if the home directory is shared across machines.
718 In this case localhost will refer to a different machine on each of
719 the machines and the user will get many warnings about changed host keys.
720 However, this option disables host authentication for localhost.
721 The argument to this keyword must be
725 The default is to check the host key for localhost.
726 .It Cm NumberOfPasswordPrompts
727 Specifies the number of password prompts before giving up.
728 The argument to this keyword must be an integer.
730 .It Cm PasswordAuthentication
731 Specifies whether to use password authentication.
732 The argument to this keyword must be
738 .It Cm PermitLocalCommand
739 Allow local command execution via the
742 .Ic !\& Ns Ar command
751 .It Cm PKCS11Provider
752 Specifies which PKCS#11 provider to use.
753 The argument to this keyword is the PKCS#11 shared libary
755 should use to communicate with a PKCS#11 token providing the user's
758 Specifies the port number to connect on the remote host.
760 .It Cm PreferredAuthentications
761 Specifies the order in which the client should try protocol 2
762 authentication methods.
763 This allows a client to prefer one method (e.g.\&
764 .Cm keyboard-interactive )
765 over another method (e.g.\&
768 .Bd -literal -offset indent
769 gssapi-with-mic,hostbased,publickey,
770 keyboard-interactive,password
773 Specifies the protocol versions
775 should support in order of preference.
776 The possible values are
780 Multiple versions must be comma-separated.
781 When this option is set to
784 will try version 2 and fall back to version 1
785 if version 2 is not available.
789 Specifies the command to use to connect to the server.
791 string extends to the end of the line, and is executed with
793 In the command string, any occurrence of
795 will be substituted by the host name to
800 by the remote user name.
801 The command can be basically anything,
802 and should read from its standard input and write to its standard output.
803 It should eventually connect an
805 server running on some machine, or execute
808 Host key management will be done using the
809 HostName of the host being connected (defaulting to the name typed by
811 Setting the command to
813 disables this option entirely.
816 is not available for connects with a proxy command.
818 This directive is useful in conjunction with
820 and its proxy support.
821 For example, the following directive would connect via an HTTP proxy at
823 .Bd -literal -offset 3n
824 ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
826 .It Cm PubkeyAuthentication
827 Specifies whether to try public key authentication.
828 The argument to this keyword must be
834 This option applies to protocol version 2 only.
836 Specifies the maximum amount of data that may be transmitted before the
837 session key is renegotiated.
838 The argument is the number of bytes, with an optional suffix of
843 to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
844 The default is between
848 depending on the cipher.
849 This option applies to protocol version 2 only.
851 Specifies that a TCP port on the remote machine be forwarded over
852 the secure channel to the specified host and port from the local machine.
853 The first argument must be
855 .Oo Ar bind_address : Oc Ar port
857 and the second argument must be
858 .Ar host : Ns Ar hostport .
859 IPv6 addresses can be specified by enclosing addresses in square brackets.
860 Multiple forwardings may be specified, and additional
861 forwardings can be given on the command line.
862 Privileged ports can be forwarded only when
863 logging in as root on the remote machine.
869 the listen port will be dynamically allocated on the server and reported
870 to the client at run time.
874 is not specified, the default is to only bind to loopback addresses.
879 or an empty string, then the forwarding is requested to listen on all
883 will only succeed if the server's
885 option is enabled (see
886 .Xr sshd_config 5 ) .
887 .It Cm RhostsRSAAuthentication
888 Specifies whether to try rhosts based authentication with RSA host
896 This option applies to protocol version 1 only and requires
899 .It Cm RSAAuthentication
900 Specifies whether to try RSA authentication.
901 The argument to this keyword must be
905 RSA authentication will only be
906 attempted if the identity file exists, or an authentication agent is
910 Note that this option applies to protocol version 1 only.
912 Specifies what variables from the local
914 should be sent to the server.
915 Note that environment passing is only supported for protocol 2.
916 The server must also support it, and the server must be configured to
917 accept these environment variables.
922 for how to configure the server.
923 Variables are specified by name, which may contain wildcard characters.
924 Multiple environment variables may be separated by whitespace or spread
928 The default is not to send any environment variables.
932 for more information on patterns.
933 .It Cm ServerAliveCountMax
934 Sets the number of server alive messages (see below) which may be
937 receiving any messages back from the server.
938 If this threshold is reached while server alive messages are being sent,
939 ssh will disconnect from the server, terminating the session.
940 It is important to note that the use of server alive messages is very
944 The server alive messages are sent through the encrypted channel
945 and therefore will not be spoofable.
946 The TCP keepalive option enabled by
949 The server alive mechanism is valuable when the client or
950 server depend on knowing when a connection has become inactive.
952 The default value is 3.
954 .Cm ServerAliveInterval
955 (see below) is set to 15 and
956 .Cm ServerAliveCountMax
957 is left at the default, if the server becomes unresponsive,
958 ssh will disconnect after approximately 45 seconds.
959 This option applies to protocol version 2 only.
960 .It Cm ServerAliveInterval
961 Sets a timeout interval in seconds after which if no data has been received
964 will send a message through the encrypted
965 channel to request a response from the server.
967 is 0, indicating that these messages will not be sent to the server.
968 This option applies to protocol version 2 only.
969 .It Cm StrictHostKeyChecking
970 If this flag is set to
973 will never automatically add host keys to the
974 .Pa ~/.ssh/known_hosts
975 file, and refuses to connect to hosts whose host key has changed.
976 This provides maximum protection against trojan horse attacks,
977 though it can be annoying when the
978 .Pa /etc/ssh/ssh_known_hosts
979 file is poorly maintained or when connections to new hosts are
981 This option forces the user to manually
983 If this flag is set to
985 ssh will automatically add new host keys to the
986 user known hosts files.
987 If this flag is set to
990 will be added to the user known host files only after the user
991 has confirmed that is what they really want to do, and
992 ssh will refuse to connect to hosts whose host key has changed.
994 known hosts will be verified automatically in all cases.
1003 Specifies whether the system should send TCP keepalive messages to the
1005 If they are sent, death of the connection or crash of one
1006 of the machines will be properly noticed.
1007 However, this means that
1008 connections will die if the route is down temporarily, and some people
1013 (to send TCP keepalive messages), and the client will notice
1014 if the network goes down or the remote host dies.
1015 This is important in scripts, and many users want it too.
1017 To disable TCP keepalive messages, the value should be set to
1022 device forwarding between the client and the server.
1023 The argument must be
1033 requests the default tunnel mode, which is
1034 .Dq point-to-point .
1040 devices to open on the client
1045 The argument must be
1047 .Ar local_tun Op : Ar remote_tun .
1049 The devices may be specified by numerical ID or the keyword
1051 which uses the next available tunnel device.
1054 is not specified, it defaults to
1058 .It Cm UsePrivilegedPort
1059 Specifies whether to use a privileged port for outgoing connections.
1060 The argument must be
1069 must be setuid root.
1070 Note that this option must be set to
1073 .Cm RhostsRSAAuthentication
1076 Specifies the user to log in as.
1077 This can be useful when a different user name is used on different machines.
1078 This saves the trouble of
1079 having to remember to give the user name on the command line.
1080 .It Cm UserKnownHostsFile
1081 Specifies a file to use for the user
1082 host key database instead of
1083 .Pa ~/.ssh/known_hosts .
1084 .It Cm VerifyHostKeyDNS
1085 Specifies whether to verify the remote key using DNS and SSHFP resource
1087 If this option is set to
1089 the client will implicitly trust keys that match a secure fingerprint
1091 Insecure fingerprints will be handled as if this option was set to
1093 If this option is set to
1095 information on fingerprint match will be displayed, but the user will still
1096 need to confirm new host keys according to the
1097 .Cm StrictHostKeyChecking
1099 The argument must be
1106 Note that this option applies to protocol version 2 only.
1109 .Sx VERIFYING HOST KEYS
1112 .It Cm VisualHostKey
1113 If this flag is set to
1115 an ASCII art representation of the remote host key fingerprint is
1116 printed in addition to the hex fingerprint string at login and
1117 for unknown host keys.
1118 If this flag is set to
1120 no fingerprint strings are printed at login and
1121 only the hex fingerprint string will be printed for unknown host keys.
1124 .It Cm XAuthLocation
1125 Specifies the full pathname of the
1129 .Pa /usr/X11R6/bin/xauth .
1134 consists of zero or more non-whitespace characters,
1136 (a wildcard that matches zero or more characters),
1139 (a wildcard that matches exactly one character).
1140 For example, to specify a set of declarations for any host in the
1143 the following pattern could be used:
1147 The following pattern
1148 would match any host in the 192.168.0.[0-9] network range:
1150 .Dl Host 192.168.0.?
1154 is a comma-separated list of patterns.
1155 Patterns within pattern-lists may be negated
1156 by preceding them with an exclamation mark
1159 to allow a key to be used from anywhere within an organisation
1163 the following entry (in authorized_keys) could be used:
1165 .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1168 .It Pa ~/.ssh/config
1169 This is the per-user configuration file.
1170 The format of this file is described above.
1171 This file is used by the SSH client.
1172 Because of the potential for abuse, this file must have strict permissions:
1173 read/write for the user, and not accessible by others.
1174 .It Pa /etc/ssh/ssh_config
1175 Systemwide configuration file.
1176 This file provides defaults for those
1177 values that are not specified in the user's configuration file, and
1178 for those users who do not have a configuration file.
1179 This file must be world-readable.
1184 OpenSSH is a derivative of the original and free
1185 ssh 1.2.12 release by Tatu Ylonen.
1186 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1187 Theo de Raadt and Dug Song
1188 removed many bugs, re-added newer features and
1190 Markus Friedl contributed the support for SSH
1191 protocol versions 1.5 and 2.0.