2 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
3 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 .\" All rights reserved
6 .\" As far as I am concerned, the code I have written for this software
7 .\" can be used freely for any purpose. Any derived versions of this
8 .\" software must be clearly marked as such, and if the derived work is
9 .\" incompatible with the protocol description in the RFC file, it must be
10 .\" called by a name other than "ssh" or "Secure Shell".
12 .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
13 .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
14 .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
16 .\" Redistribution and use in source and binary forms, with or without
17 .\" modification, are permitted provided that the following conditions
19 .\" 1. Redistributions of source code must retain the above copyright
20 .\" notice, this list of conditions and the following disclaimer.
21 .\" 2. Redistributions in binary form must reproduce the above copyright
22 .\" notice, this list of conditions and the following disclaimer in the
23 .\" documentation and/or other materials provided with the distribution.
25 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
26 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
28 .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
29 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
30 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
31 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
32 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
33 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
34 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 .\" $OpenBSD: sshd.8,v 1.304 2018/07/22 12:16:59 dtucker Exp $
38 .Dd $Mdocdate: July 22 2018 $
43 .Nd OpenSSH SSH daemon
48 .Op Fl C Ar connection_spec
49 .Op Fl c Ar host_certificate_file
51 .Op Fl f Ar config_file
52 .Op Fl g Ar login_grace_time
53 .Op Fl h Ar host_key_file
60 (OpenSSH Daemon) is the daemon program for
62 Together these programs replace rlogin and rsh,
63 and provide secure encrypted communications between two untrusted hosts
64 over an insecure network.
67 listens for connections from clients.
68 It is normally started at boot from
71 daemon for each incoming connection.
72 The forked daemons handle
73 key exchange, encryption, authentication, command execution,
77 can be configured using command-line options or a configuration file
80 command-line options override values specified in the
83 rereads its configuration file when it receives a hangup signal,
85 by executing itself with the name and options it was started with, e.g.\&
88 The options are as follows:
93 to use IPv4 addresses only.
97 to use IPv6 addresses only.
98 .It Fl C Ar connection_spec
99 Specify the connection parameters to use for the
104 directives in the configuration file that would apply are applied before the
105 configuration is written to standard output.
106 The connection parameters are supplied as keyword=value pairs and may be
107 supplied in any order, either with multiple
109 options or as a comma-separated list.
118 and correspond to source address, user, resolved source host name,
119 local address, local port number and routing domain respectively.
120 .It Fl c Ar host_certificate_file
121 Specifies a path to a certificate file to identify
124 The certificate file must match a host key file specified using the
128 configuration directive.
130 When this option is specified,
132 will not detach and does not become a daemon.
133 This allows easy monitoring of
137 The server sends verbose debug output to standard error,
138 and does not put itself in the background.
139 The server also will not fork and will only process one connection.
140 This option is only intended for debugging for the server.
143 options increase the debugging level.
148 instead of the system log.
150 Write debug logs to standard error instead of the system log.
151 .It Fl f Ar config_file
152 Specifies the name of the configuration file.
154 .Pa /etc/ssh/sshd_config .
156 refuses to start if there is no configuration file.
157 .It Fl g Ar login_grace_time
158 Gives the grace time for clients to authenticate themselves (default
160 If the client fails to authenticate the user within
161 this many seconds, the server disconnects and exits.
162 A value of zero indicates no limit.
163 .It Fl h Ar host_key_file
164 Specifies a file from which a host key is read.
165 This option must be given if
167 is not run as root (as the normal
168 host key files are normally not readable by anyone but root).
170 .Pa /etc/ssh/ssh_host_ecdsa_key ,
171 .Pa /etc/ssh/ssh_host_ed25519_key
173 .Pa /etc/ssh/ssh_host_rsa_key .
174 It is possible to have multiple host key files for
175 the different host key algorithms.
182 Can be used to give options in the format used in the configuration file.
183 This is useful for specifying options for which there is no separate
185 For full details of the options, and their values, see
188 Specifies the port on which the server listens for connections
190 Multiple port options are permitted.
191 Ports specified in the configuration file with the
193 option are ignored when a command-line port is specified.
194 Ports specified using the
196 option override command-line ports.
199 Nothing is sent to the system log.
200 Normally the beginning,
201 authentication, and termination of each connection is logged.
204 Check the validity of the configuration file, output the effective configuration
205 to stdout and then exit.
208 rules may be applied by specifying the connection parameters using one or more
213 Only check the validity of the configuration file and sanity of the keys.
214 This is useful for updating
216 reliably as configuration options may change.
218 This option is used to specify the size of the field
221 structure that holds the remote host name.
222 If the resolved host name is longer than
224 the dotted decimal value will be used instead.
225 This allows hosts with very long host names that
226 overflow this field to still be uniquely identified.
229 indicates that only dotted decimal addresses
230 should be put into the
234 may also be used to prevent
236 from making DNS requests unless the authentication
237 mechanism or configuration requires it.
238 Authentication mechanisms that may require DNS include
239 .Cm HostbasedAuthentication
241 .Cm from="pattern-list"
242 option in a key file.
243 Configuration options that require DNS include using a
250 The OpenSSH SSH daemon supports SSH protocol 2 only.
251 Each host has a host-specific key,
252 used to identify the host.
253 Whenever a client connects, the daemon responds with its public
255 The client compares the
256 host key against its own database to verify that it has not changed.
257 Forward security is provided through a Diffie-Hellman key agreement.
258 This key agreement results in a shared session key.
259 The rest of the session is encrypted using a symmetric cipher, currently
260 128-bit AES, Blowfish, 3DES, CAST128, Arcfour, 192-bit AES, or 256-bit AES.
261 The client selects the encryption algorithm
262 to use from those offered by the server.
263 Additionally, session integrity is provided
264 through a cryptographic message authentication code
265 (hmac-md5, hmac-sha1, umac-64, umac-128,
266 hmac-sha2-256 or hmac-sha2-512).
268 Finally, the server and the client enter an authentication dialog.
269 The client tries to authenticate itself using
270 host-based authentication,
271 public key authentication,
272 challenge-response authentication,
273 or password authentication.
275 Regardless of the authentication type, the account is checked to
276 ensure that it is accessible. An account is not accessible if it is
279 or its group is listed in
281 \&. The definition of a locked account is system dependent. Some platforms
282 have their own account database (eg AIX) and some modify the passwd field (
284 on Solaris and UnixWare,
291 on FreeBSD and a leading
294 If there is a requirement to disable password authentication
295 for the account while allowing still public-key, then the passwd field
296 should be set to something other than these values (eg
302 If the client successfully authenticates itself, a dialog for
303 preparing the session is entered.
304 At this time the client may request
305 things like allocating a pseudo-tty, forwarding X11 connections,
306 forwarding TCP connections, or forwarding the authentication agent
307 connection over the secure channel.
309 After this, the client either requests a shell or execution of a command.
310 The sides then enter session mode.
311 In this mode, either side may send
312 data at any time, and such data is forwarded to/from the shell or
313 command on the server side, and the user terminal in the client side.
315 When the user program terminates and all forwarded X11 and other
316 connections have been closed, the server sends command exit status to
317 the client, and both sides exit.
319 When a user successfully logs in,
322 .Bl -enum -offset indent
324 If the login is on a tty, and no command has been specified,
325 prints last login time and
327 (unless prevented in the configuration file or by
333 If the login is on a tty, records login time.
337 .Pa /var/run/nologin ;
338 if one exists, it prints the contents and quits
341 Changes to run with normal user privileges.
343 Sets up basic environment.
346 .Pa ~/.ssh/environment ,
347 if it exists, and users are allowed to change their environment.
349 .Cm PermitUserEnvironment
353 Changes to user's home directory.
360 option is set, runs it; else if
367 files are given the X11
368 authentication protocol and cookie in standard input.
373 Runs user's shell or command.
374 All commands are run under the user's login shell as specified in the
375 system password database.
382 runs it after reading the
383 environment files but before starting the user's shell or command.
384 It must not produce any output on stdout; stderr must be used
386 If X11 forwarding is in use, it will receive the "proto cookie" pair in
387 its standard input (and
394 will not run xauth automatically to add X11 cookies.
396 The primary purpose of this file is to run any initialization routines
397 which may be needed before the user's home directory becomes
398 accessible; AFS is a particular example of such an environment.
400 This file will probably contain some initialization code followed by
401 something similar to:
402 .Bd -literal -offset 3n
403 if read proto cookie && [ -n "$DISPLAY" ]; then
404 if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then
405 # X11UseLocalhost=yes
406 echo add unix:`echo $DISPLAY |
407 cut -c11-` $proto $cookie
410 echo add $DISPLAY $proto $cookie
415 If this file does not exist,
418 does not exist either, xauth is used to add the cookie.
419 .Sh AUTHORIZED_KEYS FILE FORMAT
420 .Cm AuthorizedKeysFile
421 specifies the files containing public keys for
422 public key authentication;
423 if this option is not specified, the default is
424 .Pa ~/.ssh/authorized_keys
426 .Pa ~/.ssh/authorized_keys2 .
427 Each line of the file contains one
428 key (empty lines and lines starting with a
432 Public keys consist of the following space-separated fields:
433 options, keytype, base64-encoded key, comment.
434 The options field is optional.
436 .Dq ecdsa-sha2-nistp256 ,
437 .Dq ecdsa-sha2-nistp384 ,
438 .Dq ecdsa-sha2-nistp521 ,
443 the comment field is not used for anything (but may be convenient for the
444 user to identify the key).
446 Note that lines in this file can be several hundred bytes long
447 (because of the size of the public key encoding) up to a limit of
448 8 kilobytes, which permits DSA keys up to 8 kilobits and RSA
449 keys up to 16 kilobits.
450 You don't want to type them in; instead, copy the
459 enforces a minimum RSA key modulus size of 1024 bits.
461 The options (if present) consist of comma-separated option
463 No spaces are permitted, except within double quotes.
464 The following option specifications are supported (note
465 that option keywords are case-insensitive):
467 .It Cm agent-forwarding
468 Enable authentication agent forwarding previously disabled by the
471 .It Cm cert-authority
472 Specifies that the listed key is a certification authority (CA) that is
473 trusted to validate signed certificates for user authentication.
475 Certificates may encode access restrictions similar to these key options.
476 If both certificate restrictions and key options are present, the most
477 restrictive union of the two is applied.
478 .It Cm command="command"
479 Specifies that the command is executed whenever this key is used for
481 The command supplied by the user (if any) is ignored.
482 The command is run on a pty if the client requests a pty;
483 otherwise it is run without a tty.
484 If an 8-bit clean channel is required,
485 one must not request a pty or should specify
487 A quote may be included in the command by quoting it with a backslash.
489 This option might be useful
490 to restrict certain public keys to perform just a specific operation.
491 An example might be a key that permits remote backups but nothing else.
492 Note that the client may specify TCP and/or X11
493 forwarding unless they are explicitly prohibited, e.g. using the
497 The command originally supplied by the client is available in the
498 .Ev SSH_ORIGINAL_COMMAND
499 environment variable.
500 Note that this option applies to shell, command or subsystem execution.
501 Also note that this command may be superseded by a
506 If a command is specified and a forced-command is embedded in a certificate
507 used for authentication, then the certificate will be accepted only if the
508 two commands are identical.
509 .It Cm environment="NAME=value"
510 Specifies that the string is to be added to the environment when
511 logging in using this key.
512 Environment variables set this way
513 override other default environment values.
514 Multiple options of this type are permitted.
515 Environment processing is disabled by default and is
517 .Cm PermitUserEnvironment
519 .It Cm expiry-time="timespec"
520 Specifies a time after which the key will not be accepted.
521 The time may be specified as a YYYYMMDD date or a YYYYMMDDHHMM[SS] time
522 in the system time-zone.
523 .It Cm from="pattern-list"
524 Specifies that in addition to public key authentication, either the canonical
525 name of the remote host or its IP address must be present in the
526 comma-separated list of patterns.
529 for more information on patterns.
531 In addition to the wildcard matching that may be applied to hostnames or
534 stanza may match IP addresses using CIDR address/masklen notation.
536 The purpose of this option is to optionally increase security: public key
537 authentication by itself does not trust the network or name servers or
538 anything (but the key); however, if somebody somehow steals the key, the key
539 permits an intruder to log in from anywhere in the world.
540 This additional option makes using a stolen key more difficult (name
541 servers and/or routers would have to be compromised in addition to
543 .It Cm no-agent-forwarding
544 Forbids authentication agent forwarding when this key is used for
546 .It Cm no-port-forwarding
547 Forbids TCP forwarding when this key is used for authentication.
548 Any port forward requests by the client will return an error.
549 This might be used, e.g. in connection with the
553 Prevents tty allocation (a request to allocate a pty will fail).
555 Disables execution of
557 .It Cm no-X11-forwarding
558 Forbids X11 forwarding when this key is used for authentication.
559 Any X11 forward requests by the client will return an error.
560 .It Cm permitlisten="[host:]port"
561 Limit remote port forwarding with the
564 option such that it may only listen on the specified host (optional) and port.
565 IPv6 addresses can be specified by enclosing the address in square brackets.
568 options may be applied separated by commas.
569 Hostnames may include wildcards as described in the PATTERNS section in
571 A port specification of
574 Note that the setting of
576 may further restrict listen addresses.
579 will send a hostname of
581 if a listen host was not specified when the forwarding was requested, and
582 that this name is treated differently to the explicit localhost addresses
586 .It Cm permitopen="host:port"
587 Limit local port forwarding with the
590 option such that it may only connect to the specified host and port.
591 IPv6 addresses can be specified by enclosing the address in square brackets.
594 options may be applied separated by commas.
595 No pattern matching is performed on the specified hostnames,
596 they must be literal domains or addresses.
597 A port specification of
600 .It Cm port-forwarding
601 Enable port forwarding previously disabled by the
604 .It Cm principals="principals"
607 line, specifies allowed principals for certificate authentication as a
608 comma-separated list.
609 At least one name from the list must appear in the certificate's
610 list of principals for the certificate to be accepted.
611 This option is ignored for keys that are not marked as trusted certificate
616 Permits tty allocation previously disabled by the
620 Enable all restrictions, i.e. disable port, agent and X11 forwarding,
621 as well as disabling PTY allocation
624 If any future restriction capabilities are added to authorized_keys files
625 they will be included in this set.
629 device on the server.
630 Without this option, the next available device will be used if
631 the client requests a tunnel.
635 previously disabled by the
638 .It Cm X11-forwarding
639 Permits X11 forwarding previously disabled by the
644 An example authorized_keys file:
645 .Bd -literal -offset 3n
646 # Comments allowed at start of line
647 ssh-rsa AAAAB3Nza...LiPk== user@example.net
648 from="*.sales.example.net,!pc.sales.example.net" ssh-rsa
649 AAAAB2...19Q== john@example.net
650 command="dump /home",no-pty,no-port-forwarding ssh-rsa
651 AAAAC3...51R== example.net
652 permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-rsa
654 permitlisten="localhost:8080",permitopen="localhost:22000" ssh-rsa
656 tunnel="0",command="sh /etc/netstart tun0" ssh-rsa AAAA...==
658 restrict,command="uptime" ssh-rsa AAAA1C8...32Tv==
660 restrict,pty,command="nethack" ssh-rsa AAAA1f8...IrrC5==
663 .Sh SSH_KNOWN_HOSTS FILE FORMAT
665 .Pa /etc/ssh/ssh_known_hosts
667 .Pa ~/.ssh/known_hosts
668 files contain host public keys for all known hosts.
669 The global file should
670 be prepared by the administrator (optional), and the per-user file is
671 maintained automatically: whenever the user connects to an unknown host,
672 its key is added to the per-user file.
674 Each line in these files contains the following fields: markers (optional),
675 hostnames, keytype, base64-encoded key, comment.
676 The fields are separated by spaces.
678 The marker is optional, but if it is present then it must be one of
679 .Dq @cert-authority ,
680 to indicate that the line contains a certification authority (CA) key,
683 to indicate that the key contained on the line is revoked and must not ever
685 Only one marker should be used on a key line.
687 Hostnames is a comma-separated list of patterns
692 wildcards); each pattern in turn is matched against the host name.
695 is authenticating a client, such as when using
696 .Cm HostbasedAuthentication ,
697 this will be the canonical client host name.
700 is authenticating a server, this will be the host name
701 given by the user, the value of the
704 if it was specified, or the canonical server hostname if the
706 .Cm CanonicalizeHostname
709 A pattern may also be preceded by
711 to indicate negation: if the host name matches a negated
712 pattern, it is not accepted (by that line) even if it matched another
714 A hostname or address may optionally be enclosed within
718 brackets then followed by
720 and a non-standard port number.
722 Alternately, hostnames may be stored in a hashed form which hides host names
723 and addresses should the file's contents be disclosed.
724 Hashed hostnames start with a
727 Only one hashed hostname may appear on a single line and none of the above
728 negation or wildcard operators may be applied.
730 The keytype and base64-encoded key are taken directly from the host key; they
731 can be obtained, for example, from
732 .Pa /etc/ssh/ssh_host_rsa_key.pub .
733 The optional comment field continues to the end of the line, and is not used.
737 and empty lines are ignored as comments.
739 When performing host authentication, authentication is accepted if any
740 matching line has the proper key; either one that matches exactly or,
741 if the server has presented a certificate for authentication, the key
742 of the certification authority that signed the certificate.
743 For a key to be trusted as a certification authority, it must use the
745 marker described above.
747 The known hosts file also provides a facility to mark keys as revoked,
748 for example when it is known that the associated private key has been
750 Revoked keys are specified by including the
752 marker at the beginning of the key line, and are never accepted for
753 authentication or as certification authorities, but instead will
754 produce a warning from
756 when they are encountered.
758 It is permissible (but not
759 recommended) to have several lines or different host keys for the same
761 This will inevitably happen when short forms of host names
762 from different domains are put in the file.
764 that the files contain conflicting information; authentication is
765 accepted if valid information can be found from either file.
767 Note that the lines in these files are typically hundreds of characters
768 long, and you definitely don't want to type in the host keys by hand.
769 Rather, generate them by a script,
771 or by taking, for example,
772 .Pa /etc/ssh/ssh_host_rsa_key.pub
773 and adding the host names at the front.
775 also offers some basic automated editing for
776 .Pa ~/.ssh/known_hosts
777 including removing hosts matching a host name and converting all host
778 names to their hashed representations.
780 An example ssh_known_hosts file:
781 .Bd -literal -offset 3n
782 # Comments allowed at start of line
783 closenet,...,192.0.2.53 1024 37 159...93 closenet.example.net
784 cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....=
786 |1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa
789 @revoked * ssh-rsa AAAAB5W...
790 # A CA key, accepted for any host in *.mydomain.com or *.mydomain.org
791 @cert-authority *.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W...
794 .Bl -tag -width Ds -compact
796 This file is used to suppress printing the last login time and
804 It does not suppress printing of the banner specified by
808 This file is used for host-based authentication (see
810 for more information).
811 On some machines this file may need to be
812 world-readable if the user's home directory is on an NFS partition,
816 Additionally, this file must be owned by the user,
817 and must not have write permissions for anyone else.
819 permission for most machines is read/write for the user, and not
820 accessible by others.
823 This file is used in exactly the same way as
825 but allows host-based authentication without permitting login with
829 This directory is the default location for all user-specific configuration
830 and authentication information.
831 There is no general requirement to keep the entire contents of this directory
832 secret, but the recommended permissions are read/write/execute for the user,
833 and not accessible by others.
835 .It Pa ~/.ssh/authorized_keys
836 Lists the public keys (DSA, ECDSA, Ed25519, RSA)
837 that can be used for logging in as this user.
838 The format of this file is described above.
839 The content of the file is not highly sensitive, but the recommended
840 permissions are read/write for the user, and not accessible by others.
844 directory, or the user's home directory are writable
845 by other users, then the file could be modified or replaced by unauthorized
849 will not allow it to be used unless the
851 option has been set to
854 .It Pa ~/.ssh/environment
855 This file is read into the environment at login (if it exists).
856 It can only contain empty lines, comment lines (that start with
858 and assignment lines of the form name=value.
859 The file should be writable
860 only by the user; it need not be readable by anyone else.
861 Environment processing is disabled by default and is
863 .Cm PermitUserEnvironment
866 .It Pa ~/.ssh/known_hosts
867 Contains a list of host keys for all hosts the user has logged into
868 that are not already in the systemwide list of known host keys.
869 The format of this file is described above.
870 This file should be writable only by root/the owner and
871 can, but need not be, world-readable.
874 Contains initialization routines to be run before
875 the user's home directory becomes accessible.
876 This file should be writable only by the user, and need not be
877 readable by anyone else.
879 .It Pa /etc/hosts.allow
880 .It Pa /etc/hosts.deny
881 Access controls that should be enforced by tcp-wrappers are defined here.
882 Further details are described in
885 .It Pa /etc/hosts.equiv
886 This file is for host-based authentication (see
888 It should only be writable by root.
891 Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange"
893 The file format is described in
895 If no usable groups are found in this file then fixed internal groups will
905 refuses to let anyone except root log in.
906 The contents of the file
907 are displayed to anyone trying to log in, and non-root connections are
909 The file should be world-readable.
911 .It Pa /etc/shosts.equiv
912 This file is used in exactly the same way as
914 but allows host-based authentication without permitting login with
917 .It Pa /etc/ssh/ssh_host_ecdsa_key
918 .It Pa /etc/ssh/ssh_host_ed25519_key
919 .It Pa /etc/ssh/ssh_host_rsa_key
920 These files contain the private parts of the host keys.
921 These files should only be owned by root, readable only by root, and not
922 accessible to others.
925 does not start if these files are group/world-accessible.
927 .It Pa /etc/ssh/ssh_host_ecdsa_key.pub
928 .It Pa /etc/ssh/ssh_host_ed25519_key.pub
929 .It Pa /etc/ssh/ssh_host_rsa_key.pub
930 These files contain the public parts of the host keys.
931 These files should be world-readable but writable only by
933 Their contents should match the respective private parts.
935 really used for anything; they are provided for the convenience of
936 the user so their contents can be copied to known hosts files.
937 These files are created using
940 .It Pa /etc/ssh/ssh_known_hosts
941 Systemwide list of known host keys.
942 This file should be prepared by the
943 system administrator to contain the public host keys of all machines in the
945 The format of this file is described above.
946 This file should be writable only by root/the owner and
947 should be world-readable.
949 .It Pa /etc/ssh/sshd_config
950 Contains configuration data for
952 The file format and configuration options are described in
955 .It Pa /etc/ssh/sshrc
958 it can be used to specify
959 machine-specific login-time initializations globally.
960 This file should be writable only by root, and should be world-readable.
966 during privilege separation in the pre-authentication phase.
967 The directory should not contain any files and must be owned by root
968 and not group or world-writable.
970 .It Pa /var/run/sshd.pid
971 Contains the process ID of the
973 listening for connections (if there are several daemons running
974 concurrently for different ports, this contains the process ID of the one
976 The content of this file is not sensitive; it can be world-readable.
994 OpenSSH is a derivative of the original and free
995 ssh 1.2.12 release by Tatu Ylonen.
996 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
997 Theo de Raadt and Dug Song
998 removed many bugs, re-added newer features and
1000 Markus Friedl contributed the support for SSH
1001 protocol versions 1.5 and 2.0.
1002 Niels Provos and Markus Friedl contributed support
1003 for privilege separation.