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.1,v 1.184 2004/04/28 07:13:42 jmc Exp $
38 .Dd September 25, 1999
43 .Nd OpenSSH SSH client (remote login program)
46 .Op Fl 1246AaCfgkNnqsTtVvXxY
47 .Op Fl b Ar bind_address
48 .Op Fl c Ar cipher_spec
50 .Op Fl e Ar escape_char
51 .Op Fl F Ar configfile
52 .Op Fl i Ar identity_file
63 .Op Fl l Ar login_name
77 .Oo Ar user Ns @ Oc Ns Ar hostname
81 (SSH client) is a program for logging into a remote machine and for
82 executing commands on a remote machine.
83 It is intended to replace rlogin and rsh,
84 and provide secure encrypted communications between
85 two untrusted hosts over an insecure network.
86 X11 connections and arbitrary TCP/IP ports
87 can also be forwarded over the secure channel.
90 connects and logs into the specified
96 his/her identity to the remote machine using one of several methods
97 depending on the protocol version used.
103 is executed on the remote host instead of a login shell.
104 .Ss SSH protocol version 1
105 First, if the machine the user logs in from is listed in
108 .Pa /etc/shosts.equiv
109 on the remote machine, and the user names are
110 the same on both sides, the user is immediately permitted to log in.
115 exists in the user's home directory on the
116 remote machine and contains a line containing the name of the client
117 machine and the name of the user on that machine, the user is
119 This form of authentication alone is normally not
120 allowed by the server because it is not secure.
122 The second authentication method is the
126 method combined with RSA-based host authentication.
127 It means that if the login would be permitted by
130 .Pa /etc/hosts.equiv ,
132 .Pa /etc/shosts.equiv ,
133 and if additionally the server can verify the client's
135 .Pa /etc/ssh/ssh_known_hosts
137 .Pa $HOME/.ssh/known_hosts
140 section), only then is login permitted.
141 This authentication method closes security holes due to IP
142 spoofing, DNS spoofing and routing spoofing.
143 [Note to the administrator:
144 .Pa /etc/hosts.equiv ,
146 and the rlogin/rsh protocol in general, are inherently insecure and should be
147 disabled if security is desired.]
149 As a third authentication method,
151 supports RSA based authentication.
152 The scheme is based on public-key cryptography: there are cryptosystems
153 where encryption and decryption are done using separate keys, and it
154 is not possible to derive the decryption key from the encryption key.
155 RSA is one such system.
156 The idea is that each user creates a public/private
157 key pair for authentication purposes.
158 The server knows the public key, and only the user knows the private key.
161 .Pa $HOME/.ssh/authorized_keys
162 lists the public keys that are permitted for logging in.
163 When the user logs in, the
165 program tells the server which key pair it would like to use for
167 The server checks if this key is permitted, and if so,
168 sends the user (actually the
170 program running on behalf of the user) a challenge, a random number,
171 encrypted by the user's public key.
172 The challenge can only be decrypted using the proper private key.
173 The user's client then decrypts the challenge using the private key,
174 proving that he/she knows the private key
175 but without disclosing it to the server.
178 implements the RSA authentication protocol automatically.
179 The user creates his/her RSA key pair by running
181 This stores the private key in
182 .Pa $HOME/.ssh/identity
183 and stores the public key in
184 .Pa $HOME/.ssh/identity.pub
185 in the user's home directory.
186 The user should then copy the
189 .Pa $HOME/.ssh/authorized_keys
190 in his/her home directory on the remote machine (the
192 file corresponds to the conventional
194 file, and has one key
195 per line, though the lines can be very long).
196 After this, the user can log in without giving the password.
197 RSA authentication is much more secure than
201 The most convenient way to use RSA authentication may be with an
202 authentication agent.
205 for more information.
207 If other authentication methods fail,
209 prompts the user for a password.
210 The password is sent to the remote
211 host for checking; however, since all communications are encrypted,
212 the password cannot be seen by someone listening on the network.
213 .Ss SSH protocol version 2
214 When a user connects using protocol version 2,
215 similar authentication methods are available.
216 Using the default values for
217 .Cm PreferredAuthentications ,
218 the client will try to authenticate first using the hostbased method;
219 if this method fails, public key authentication is attempted,
220 and finally if this method fails, keyboard-interactive and
221 password authentication are tried.
223 The public key method is similar to RSA authentication described
224 in the previous section and allows the RSA or DSA algorithm to be used:
225 The client uses his private key,
226 .Pa $HOME/.ssh/id_dsa
228 .Pa $HOME/.ssh/id_rsa ,
229 to sign the session identifier and sends the result to the server.
230 The server checks whether the matching public key is listed in
231 .Pa $HOME/.ssh/authorized_keys
232 and grants access if both the key is found and the signature is correct.
233 The session identifier is derived from a shared Diffie-Hellman value
234 and is only known to the client and the server.
236 If public key authentication fails or is not available, a password
237 can be sent encrypted to the remote host to prove the user's identity.
241 supports hostbased or challenge response authentication.
243 Protocol 2 provides additional mechanisms for confidentiality
244 (the traffic is encrypted using 3DES, Blowfish, CAST128 or Arcfour)
245 and integrity (hmac-md5, hmac-sha1).
246 Note that protocol 1 lacks a strong mechanism for ensuring the
247 integrity of the connection.
248 .Ss Login session and remote execution
249 When the user's identity has been accepted by the server, the server
250 either executes the given command, or logs into the machine and gives
251 the user a normal shell on the remote machine.
252 All communication with
253 the remote command or shell will be automatically encrypted.
255 If a pseudo-terminal has been allocated (normal login session), the
256 user may use the escape characters noted below.
258 If no pseudo-tty has been allocated,
259 the session is transparent and can be used to reliably transfer binary data.
260 On most systems, setting the escape character to
262 will also make the session transparent even if a tty is used.
264 The session terminates when the command or shell on the remote
265 machine exits and all X11 and TCP/IP connections have been closed.
266 The exit status of the remote program is returned as the exit status of
268 .Ss Escape Characters
269 When a pseudo-terminal has been requested,
271 supports a number of functions through the use of an escape character.
273 A single tilde character can be sent as
275 or by following the tilde by a character other than those described below.
276 The escape character must always follow a newline to be interpreted as
278 The escape character can be changed in configuration files using the
280 configuration directive or on the command line by the
284 The supported escapes (assuming the default
294 List forwarded connections.
298 at logout when waiting for forwarded connection / X11 sessions to terminate.
300 Display a list of escape characters.
302 Send a BREAK to the remote system
303 (only useful for SSH protocol version 2 and if the peer supports it).
305 Open command line (only useful for adding port forwardings using the
311 Request rekeying of the connection
312 (only useful for SSH protocol version 2 and if the peer supports it).
314 .Ss X11 and TCP forwarding
319 (or see the description of the
323 options described later)
324 and the user is using X11 (the
326 environment variable is set), the connection to the X11 display is
327 automatically forwarded to the remote side in such a way that any X11
328 programs started from the shell (or command) will go through the
329 encrypted channel, and the connection to the real X server will be made
330 from the local machine.
331 The user should not manually set
333 Forwarding of X11 connections can be
334 configured on the command line or in configuration files.
340 will point to the server machine, but with a display number greater than zero.
341 This is normal, and happens because
345 X server on the server machine for forwarding the
346 connections over the encrypted channel.
349 will also automatically set up Xauthority data on the server machine.
350 For this purpose, it will generate a random authorization cookie,
351 store it in Xauthority on the server, and verify that any forwarded
352 connections carry this cookie and replace it by the real cookie when
353 the connection is opened.
354 The real authentication cookie is never
355 sent to the server machine (and no cookies are sent in the plain).
361 (or see the description of the
365 options described later) and
366 the user is using an authentication agent, the connection to the agent
367 is automatically forwarded to the remote side.
369 Forwarding of arbitrary TCP/IP connections over the secure channel can
370 be specified either on the command line or in a configuration file.
371 One possible application of TCP/IP forwarding is a secure connection to an
372 electronic purse; another is going through firewalls.
373 .Ss Server authentication
375 automatically maintains and checks a database containing
376 identifications for all hosts it has ever been used with.
377 Host keys are stored in
378 .Pa $HOME/.ssh/known_hosts
379 in the user's home directory.
380 Additionally, the file
381 .Pa /etc/ssh/ssh_known_hosts
382 is automatically checked for known hosts.
383 Any new hosts are automatically added to the user's file.
384 If a host's identification ever changes,
386 warns about this and disables password authentication to prevent a
387 trojan horse from getting the user's password.
388 Another purpose of this mechanism is to prevent man-in-the-middle attacks
389 which could otherwise be used to circumvent the encryption.
391 .Cm StrictHostKeyChecking
392 option can be used to prevent logins to machines whose
393 host key is not known or has changed.
395 The options are as follows:
400 to try protocol version 1 only.
404 to try protocol version 2 only.
408 to use IPv4 addresses only.
412 to use IPv6 addresses only.
414 Enables forwarding of the authentication agent connection.
415 This can also be specified on a per-host basis in a configuration file.
417 Agent forwarding should be enabled with caution.
418 Users with the ability to bypass file permissions on the remote host
419 (for the agent's Unix-domain socket)
420 can access the local agent through the forwarded connection.
421 An attacker cannot obtain key material from the agent,
422 however they can perform operations on the keys that enable them to
423 authenticate using the identities loaded into the agent.
425 Disables forwarding of the authentication agent connection.
426 .It Fl b Ar bind_address
427 Specify the interface to transmit from on machines with multiple
428 interfaces or aliased addresses.
430 Requests compression of all data (including stdin, stdout, stderr, and
431 data for forwarded X11 and TCP/IP connections).
432 The compression algorithm is the same used by
436 can be controlled by the
438 option for protocol version 1.
439 Compression is desirable on modem lines and other
440 slow connections, but will only slow down things on fast networks.
441 The default value can be set on a host-by-host basis in the
442 configuration files; see the
445 .It Fl c Ar blowfish | 3des | des
446 Selects the cipher to use for encrypting the session.
449 It is believed to be secure.
451 (triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
453 is a fast block cipher; it appears very secure and is much faster than
456 is only supported in the
458 client for interoperability with legacy protocol 1 implementations
459 that do not support the
462 Its use is strongly discouraged due to cryptographic weaknesses.
463 .It Fl c Ar cipher_spec
464 Additionally, for protocol version 2 a comma-separated list of ciphers can
465 be specified in order of preference.
468 for more information.
472 application-level port forwarding.
473 This works by allocating a socket to listen to
475 on the local side, and whenever a connection is made to this port, the
476 connection is forwarded over the secure channel, and the application
477 protocol is then used to determine where to connect to from the
479 Currently the SOCKS4 and SOCKS5 protocols are supported, and
481 will act as a SOCKS server.
482 Only root can forward privileged ports.
483 Dynamic port forwardings can also be specified in the configuration file.
484 .It Fl e Ar ch | ^ch | none
485 Sets the escape character for sessions with a pty (default:
487 The escape character is only recognized at the beginning of a line.
488 The escape character followed by a dot
490 closes the connection;
491 followed by control-Z suspends the connection;
492 and followed by itself sends the escape character once.
493 Setting the character to
495 disables any escapes and makes the session fully transparent.
496 .It Fl F Ar configfile
497 Specifies an alternative per-user configuration file.
498 If a configuration file is given on the command line,
499 the system-wide configuration file
500 .Pq Pa /etc/ssh/ssh_config
502 The default for the per-user configuration file is
503 .Pa $HOME/.ssh/config .
507 to go to background just before command execution.
510 is going to ask for passwords or passphrases, but the user
511 wants it in the background.
514 The recommended way to start X11 programs at a remote site is with
516 .Ic ssh -f host xterm .
518 Allows remote hosts to connect to local forwarded ports.
519 .It Fl I Ar smartcard_device
520 Specifies which smartcard device to use.
521 The argument is the device
523 should use to communicate with a smartcard used for storing the user's
525 .It Fl i Ar identity_file
526 Selects a file from which the identity (private key) for
527 RSA or DSA authentication is read.
529 .Pa $HOME/.ssh/identity
530 for protocol version 1, and
531 .Pa $HOME/.ssh/id_rsa
533 .Pa $HOME/.ssh/id_dsa
534 for protocol version 2.
535 Identity files may also be specified on
536 a per-host basis in the configuration file.
537 It is possible to have multiple
539 options (and multiple identities specified in
540 configuration files).
542 Disables forwarding (delegation) of GSSAPI credentials to the server.
545 .Ar port : host : hostport
548 Specifies that the given port on the local (client) host is to be
549 forwarded to the given host and port on the remote side.
550 This works by allocating a socket to listen to
552 on the local side, and whenever a connection is made to this port, the
553 connection is forwarded over the secure channel, and a connection is
558 from the remote machine.
559 Port forwardings can also be specified in the configuration file.
560 Only root can forward privileged ports.
561 IPv6 addresses can be specified with an alternative syntax:
564 .Ar port No / Ar host No /
568 .It Fl l Ar login_name
569 Specifies the user to log in as on the remote machine.
570 This also may be specified on a per-host basis in the configuration file.
572 Additionally, for protocol version 2 a comma-separated list of MAC
573 (message authentication code) algorithms can
574 be specified in order of preference.
577 keyword for more information.
579 Do not execute a remote command.
580 This is useful for just forwarding ports
581 (protocol version 2 only).
585 (actually, prevents reading from stdin).
586 This must be used when
588 is run in the background.
589 A common trick is to use this to run X11 programs on a remote machine.
591 .Ic ssh -n shadows.cs.hut.fi emacs &
592 will start an emacs on shadows.cs.hut.fi, and the X11
593 connection will be automatically forwarded over an encrypted channel.
596 program will be put in the background.
597 (This does not work if
599 needs to ask for a password or passphrase; see also the
603 Can be used to give options in the format used in the configuration file.
604 This is useful for specifying options for which there is no separate
606 For full details of the options listed below, and their possible values, see
609 .Bl -tag -width Ds -offset indent -compact
613 .It ChallengeResponseAuthentication
617 .It ClearAllForwardings
620 .It ConnectionAttempts
621 .It ConnectionTimeout
626 .It ForwardX11Trusted
628 .It GlobalKnownHostsFile
629 .It GSSAPIAuthentication
630 .It GSSAPIDelegateCredentials
632 .It HostbasedAuthentication
633 .It HostKeyAlgorithms
641 .It NoHostAuthenticationForLocalhost
642 .It NumberOfPasswordPrompts
643 .It PasswordAuthentication
645 .It PreferredAuthentications
648 .It PubkeyAuthentication
650 .It RhostsRSAAuthentication
651 .It RSAAuthentication
653 .It ServerAliveInterval
654 .It ServerAliveCountMax
656 .It StrictHostKeyChecking
658 .It UsePrivilegedPort
660 .It UserKnownHostsFile
665 Port to connect to on the remote host.
666 This can be specified on a
667 per-host basis in the configuration file.
670 Causes all warning and diagnostic messages to be suppressed.
673 .Ar port : host : hostport
676 Specifies that the given port on the remote (server) host is to be
677 forwarded to the given host and port on the local side.
678 This works by allocating a socket to listen to
680 on the remote side, and whenever a connection is made to this port, the
681 connection is forwarded over the secure channel, and a connection is
686 from the local machine.
687 Port forwardings can also be specified in the configuration file.
688 Privileged ports can be forwarded only when
689 logging in as root on the remote machine.
690 IPv6 addresses can be specified with an alternative syntax:
693 .Ar port No / Ar host No /
698 May be used to request invocation of a subsystem on the remote system.
699 Subsystems are a feature of the SSH2 protocol which facilitate the use
700 of SSH as a secure transport for other applications (eg.\&
702 The subsystem is specified as the remote command.
704 Disable pseudo-tty allocation.
706 Force pseudo-tty allocation.
707 This can be used to execute arbitrary
708 screen-based programs on a remote machine, which can be very useful,
709 e.g., when implementing menu services.
712 options force tty allocation, even if
716 Display the version number and exit.
721 to print debugging messages about its progress.
723 debugging connection, authentication, and configuration problems.
726 options increase the verbosity.
729 Enables X11 forwarding.
730 This can also be specified on a per-host basis in a configuration file.
732 X11 forwarding should be enabled with caution.
733 Users with the ability to bypass file permissions on the remote host
734 (for the user's X authorization database)
735 can access the local X11 display through the forwarded connection.
736 An attacker may then be able to perform activities such as keystroke monitoring.
738 Disables X11 forwarding.
740 Enables trusted X11 forwarding.
742 .Sh CONFIGURATION FILES
744 may additionally obtain configuration data from
745 a per-user configuration file and a system-wide configuration file.
746 The file format and configuration options are described in
750 will normally set the following environment variables:
751 .Bl -tag -width LOGNAME
755 variable indicates the location of the X11 server.
756 It is automatically set by
758 to point to a value of the form
760 where hostname indicates
761 the host where the shell runs, and n is an integer \*(Ge 1.
763 uses this special value to forward X11 connections over the secure
765 The user should normally not set
768 will render the X11 connection insecure (and will require the user to
769 manually copy any required authorization cookies).
771 Set to the path of the user's home directory.
775 set for compatibility with systems that use this variable.
777 Set to the path of the user's mailbox.
781 as specified when compiling
786 needs a passphrase, it will read the passphrase from the current
787 terminal if it was run from a terminal.
790 does not have a terminal associated with it but
794 are set, it will execute the program specified by
796 and open an X11 window to read the passphrase.
797 This is particularly useful when calling
802 (Note that on some machines it
803 may be necessary to redirect the input from
807 Identifies the path of a unix-domain socket used to communicate with the
809 .It Ev SSH_CONNECTION
810 Identifies the client and server ends of the connection.
811 The variable contains
812 four space-separated values: client ip-address, client port number,
813 server ip-address and server port number.
814 .It Ev SSH_ORIGINAL_COMMAND
815 The variable contains the original command line if a forced command
817 It can be used to extract the original arguments.
819 This is set to the name of the tty (path to the device) associated
820 with the current shell or command.
821 If the current session has no tty,
822 this variable is not set.
824 The timezone variable is set to indicate the present timezone if it
825 was set when the daemon was started (i.e., the daemon passes the value
826 on to new connections).
828 Set to the name of the user logging in.
834 .Pa $HOME/.ssh/environment ,
835 and adds lines of the format
837 to the environment if the file exists and if users are allowed to
838 change their environment.
839 For more information, see the
840 .Cm PermitUserEnvironment
845 .It Pa $HOME/.ssh/known_hosts
846 Records host keys for all hosts the user has logged into that are not
848 .Pa /etc/ssh/ssh_known_hosts .
851 .It Pa $HOME/.ssh/identity, $HOME/.ssh/id_dsa, $HOME/.ssh/id_rsa
852 Contains the authentication identity of the user.
853 They are for protocol 1 RSA, protocol 2 DSA, and protocol 2 RSA, respectively.
855 contain sensitive data and should be readable by the user but not
856 accessible by others (read/write/execute).
859 ignores a private key file if it is accessible by others.
860 It is possible to specify a passphrase when
861 generating the key; the passphrase will be used to encrypt the
862 sensitive part of this file using 3DES.
863 .It Pa $HOME/.ssh/identity.pub, $HOME/.ssh/id_dsa.pub, $HOME/.ssh/id_rsa.pub
864 Contains the public key for authentication (public part of the
865 identity file in human-readable form).
867 .Pa $HOME/.ssh/identity.pub
868 file should be added to the file
869 .Pa $HOME/.ssh/authorized_keys
871 where the user wishes to log in using protocol version 1 RSA authentication.
873 .Pa $HOME/.ssh/id_dsa.pub
875 .Pa $HOME/.ssh/id_rsa.pub
876 file should be added to
877 .Pa $HOME/.ssh/authorized_keys
879 where the user wishes to log in using protocol version 2 DSA/RSA authentication.
881 sensitive and can (but need not) be readable by anyone.
883 never used automatically and are not necessary; they are only provided for
884 the convenience of the user.
885 .It Pa $HOME/.ssh/config
886 This is the per-user configuration file.
887 The file format and configuration options are described in
889 Because of the potential for abuse, this file must have strict permissions:
890 read/write for the user, and not accessible by others.
891 .It Pa $HOME/.ssh/authorized_keys
892 Lists the public keys (RSA/DSA) that can be used for logging in as this user.
893 The format of this file is described in the
896 In the simplest form the format is the same as the
899 This file is not highly sensitive, but the recommended
900 permissions are read/write for the user, and not accessible by others.
901 .It Pa /etc/ssh/ssh_known_hosts
902 Systemwide list of known host keys.
903 This file should be prepared by the
904 system administrator to contain the public host keys of all machines in the
906 This file should be world-readable.
908 public keys, one per line, in the following format (fields separated
909 by spaces): system name, public key and optional comment field.
910 When different names are used
911 for the same machine, all such names should be listed, separated by
913 The format is described in the
917 The canonical system name (as returned by name servers) is used by
919 to verify the client host when logging in; other names are needed because
921 does not convert the user-supplied name to a canonical name before
922 checking the key, because someone with access to the name servers
923 would then be able to fool host authentication.
924 .It Pa /etc/ssh/ssh_config
925 Systemwide configuration file.
926 The file format and configuration options are described in
928 .It Pa /etc/ssh/ssh_host_key, /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_rsa_key
929 These three files contain the private parts of the host keys
931 .Cm RhostsRSAAuthentication
933 .Cm HostbasedAuthentication .
934 If the protocol version 1
935 .Cm RhostsRSAAuthentication
938 must be setuid root, since the host key is readable only by root.
939 For protocol version 2,
943 to access the host keys for
944 .Cm HostbasedAuthentication .
945 This eliminates the requirement that
947 be setuid root when that authentication method is used.
954 authentication to list the
955 host/user pairs that are permitted to log in.
956 (Note that this file is
957 also used by rlogin and rsh, which makes using this file insecure.)
958 Each line of the file contains a host name (in the canonical form
959 returned by name servers), and then a user name on that host,
960 separated by a space.
961 On some machines this file may need to be
962 world-readable if the user's home directory is on a NFS partition,
966 Additionally, this file must be owned by the user,
967 and must not have write permissions for anyone else.
969 permission for most machines is read/write for the user, and not
970 accessible by others.
974 will be installed so that it requires successful RSA host
975 authentication before permitting
978 If the server machine does not have the client's host key in
979 .Pa /etc/ssh/ssh_known_hosts ,
981 .Pa $HOME/.ssh/known_hosts .
982 The easiest way to do this is to
983 connect back to the client from the server machine using ssh; this
984 will automatically add the host key to
985 .Pa $HOME/.ssh/known_hosts .
987 This file is used exactly the same way as
990 having this file is to be able to use rhosts authentication with
992 without permitting login with
996 .It Pa /etc/hosts.equiv
997 This file is used during
1001 canonical hosts names, one per line (the full format is described in the
1004 If the client host is found in this file, login is
1005 automatically permitted provided client and server user names are the
1007 Additionally, successful RSA host authentication is normally
1009 This file should only be writable by root.
1010 .It Pa /etc/shosts.equiv
1011 This file is processed exactly as
1012 .Pa /etc/hosts.equiv .
1013 This file may be useful to permit logins using
1015 but not using rsh/rlogin.
1016 .It Pa /etc/ssh/sshrc
1017 Commands in this file are executed by
1019 when the user logs in just before the user's shell (or command) is started.
1022 manual page for more information.
1023 .It Pa $HOME/.ssh/rc
1024 Commands in this file are executed by
1026 when the user logs in just before the user's shell (or command) is
1030 manual page for more information.
1031 .It Pa $HOME/.ssh/environment
1032 Contains additional definitions for environment variables, see section
1038 exits with the exit status of the remote command or with 255
1039 if an error occurred.
1059 .%T "SSH Protocol Architecture"
1060 .%N draft-ietf-secsh-architecture-12.txt
1062 .%O work in progress material
1065 OpenSSH is a derivative of the original and free
1066 ssh 1.2.12 release by Tatu Ylonen.
1067 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1068 Theo de Raadt and Dug Song
1069 removed many bugs, re-added newer features and
1071 Markus Friedl contributed the support for SSH
1072 protocol versions 1.5 and 2.0.
andersk / openssh.git / blob