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 1.322 2023/01/18 01:50:21 millert Exp $
37 .Dd $Mdocdate: January 18 2023 $
47 .Op Fl C Ar connection_spec
48 .Op Fl c Ar host_certificate_file
50 .Op Fl f Ar config_file
51 .Op Fl g Ar login_grace_time
52 .Op Fl h Ar host_key_file
59 (OpenSSH Daemon) is the daemon program for
61 It provides secure encrypted communications between two untrusted hosts
62 over an insecure network.
65 listens for connections from clients.
66 It is normally started at boot from
69 daemon for each incoming connection.
70 The forked daemons handle
71 key exchange, encryption, authentication, command execution,
75 can be configured using command-line options or a configuration file
78 command-line options override values specified in the
81 rereads its configuration file when it receives a hangup signal,
83 by executing itself with the name and options it was started with, e.g.\&
86 The options are as follows:
91 to use IPv4 addresses only.
95 to use IPv6 addresses only.
96 .It Fl C Ar connection_spec
97 Specify the connection parameters to use for the
102 directives in the configuration file that would apply are applied before the
103 configuration is written to standard output.
104 The connection parameters are supplied as keyword=value pairs and may be
105 supplied in any order, either with multiple
107 options or as a comma-separated list.
116 and correspond to source address, user, resolved source host name,
117 local address, local port number and routing domain respectively.
118 .It Fl c Ar host_certificate_file
119 Specifies a path to a certificate file to identify
122 The certificate file must match a host key file specified using the
126 configuration directive.
128 When this option is specified,
130 will not detach and does not become a daemon.
131 This allows easy monitoring of
135 The server sends verbose debug output to standard error,
136 and does not put itself in the background.
137 The server also will not
139 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
249 Display the version number and exit.
252 The OpenSSH SSH daemon supports SSH protocol 2 only.
253 Each host has a host-specific key,
254 used to identify the host.
255 Whenever a client connects, the daemon responds with its public
257 The client compares the
258 host key against its own database to verify that it has not changed.
259 Forward secrecy is provided through a Diffie-Hellman key agreement.
260 This key agreement results in a shared session key.
261 The rest of the session is encrypted using a symmetric cipher.
262 The client selects the encryption algorithm
263 to use from those offered by the server.
264 Additionally, session integrity is provided
265 through a cryptographic message authentication code (MAC).
267 Finally, the server and the client enter an authentication dialog.
268 The client tries to authenticate itself using
269 host-based authentication,
270 public key authentication,
271 challenge-response authentication,
272 or password authentication.
274 Regardless of the authentication type, the account is checked to
275 ensure that it is accessible. An account is not accessible if it is
278 or its group is listed in
280 \&. The definition of a locked account is system dependent. Some platforms
281 have their own account database (eg AIX) and some modify the passwd field (
283 on Solaris and UnixWare,
290 on FreeBSD and a leading
293 If there is a requirement to disable password authentication
294 for the account while allowing still public-key, then the passwd field
295 should be set to something other than these values (eg
301 If the client successfully authenticates itself, a dialog for
302 preparing the session is entered.
303 At this time the client may request
304 things like allocating a pseudo-tty, forwarding X11 connections,
305 forwarding TCP connections, or forwarding the authentication agent
306 connection over the secure channel.
308 After this, the client either requests an interactive shell or execution
309 or a non-interactive command, which
311 will execute via the user's shell using its
314 The sides then enter session mode.
315 In this mode, either side may send
316 data at any time, and such data is forwarded to/from the shell or
317 command on the server side, and the user terminal in the client side.
319 When the user program terminates and all forwarded X11 and other
320 connections have been closed, the server sends command exit status to
321 the client, and both sides exit.
323 When a user successfully logs in,
326 .Bl -enum -offset indent
328 If the login is on a tty, and no command has been specified,
329 prints last login time and
331 (unless prevented in the configuration file or by
337 If the login is on a tty, records login time.
341 .Pa /var/run/nologin ;
342 if one exists, it prints the contents and quits
345 Changes to run with normal user privileges.
347 Sets up basic environment.
350 .Pa ~/.ssh/environment ,
351 if it exists, and users are allowed to change their environment.
353 .Cm PermitUserEnvironment
357 Changes to user's home directory.
364 option is set, runs it; else if
371 files are given the X11
372 authentication protocol and cookie in standard input.
377 Runs user's shell or command.
378 All commands are run under the user's login shell as specified in the
379 system password database.
386 runs it after reading the
387 environment files but before starting the user's shell or command.
388 It must not produce any output on stdout; stderr must be used
390 If X11 forwarding is in use, it will receive the "proto cookie" pair in
391 its standard input (and
398 will not run xauth automatically to add X11 cookies.
400 The primary purpose of this file is to run any initialization routines
401 which may be needed before the user's home directory becomes
402 accessible; AFS is a particular example of such an environment.
404 This file will probably contain some initialization code followed by
405 something similar to:
406 .Bd -literal -offset 3n
407 if read proto cookie && [ -n "$DISPLAY" ]; then
408 if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then
409 # X11UseLocalhost=yes
410 echo add unix:`echo $DISPLAY |
411 cut -c11-` $proto $cookie
414 echo add $DISPLAY $proto $cookie
419 If this file does not exist,
422 does not exist either, xauth is used to add the cookie.
423 .Sh AUTHORIZED_KEYS FILE FORMAT
424 .Cm AuthorizedKeysFile
425 specifies the files containing public keys for
426 public key authentication;
427 if this option is not specified, the default is
428 .Pa ~/.ssh/authorized_keys
430 .Pa ~/.ssh/authorized_keys2 .
431 Each line of the file contains one
432 key (empty lines and lines starting with a
436 Public keys consist of the following space-separated fields:
437 options, keytype, base64-encoded key, comment.
438 The options field is optional.
439 The supported key types are:
441 .Bl -item -compact -offset indent
443 sk-ecdsa-sha2-nistp256@openssh.com
451 sk-ssh-ed25519@openssh.com
460 The comment field is not used for anything (but may be convenient for the
461 user to identify the key).
463 Note that lines in this file can be several hundred bytes long
464 (because of the size of the public key encoding) up to a limit of
465 8 kilobytes, which permits RSA keys up to 16 kilobits.
466 You don't want to type them in; instead, copy the
469 .Pa id_ecdsa_sk.pub ,
471 .Pa id_ed25519_sk.pub ,
477 enforces a minimum RSA key modulus size of 1024 bits.
479 The options (if present) consist of comma-separated option
481 No spaces are permitted, except within double quotes.
482 The following option specifications are supported (note
483 that option keywords are case-insensitive):
485 .It Cm agent-forwarding
486 Enable authentication agent forwarding previously disabled by the
489 .It Cm cert-authority
490 Specifies that the listed key is a certification authority (CA) that is
491 trusted to validate signed certificates for user authentication.
493 Certificates may encode access restrictions similar to these key options.
494 If both certificate restrictions and key options are present, the most
495 restrictive union of the two is applied.
496 .It Cm command="command"
497 Specifies that the command is executed whenever this key is used for
499 The command supplied by the user (if any) is ignored.
500 The command is run on a pty if the client requests a pty;
501 otherwise it is run without a tty.
502 If an 8-bit clean channel is required,
503 one must not request a pty or should specify
505 A quote may be included in the command by quoting it with a backslash.
507 This option might be useful
508 to restrict certain public keys to perform just a specific operation.
509 An example might be a key that permits remote backups but nothing else.
510 Note that the client may specify TCP and/or X11
511 forwarding unless they are explicitly prohibited, e.g. using the
515 The command originally supplied by the client is available in the
516 .Ev SSH_ORIGINAL_COMMAND
517 environment variable.
518 Note that this option applies to shell, command or subsystem execution.
519 Also note that this command may be superseded by a
524 If a command is specified and a forced-command is embedded in a certificate
525 used for authentication, then the certificate will be accepted only if the
526 two commands are identical.
527 .It Cm environment="NAME=value"
528 Specifies that the string is to be added to the environment when
529 logging in using this key.
530 Environment variables set this way
531 override other default environment values.
532 Multiple options of this type are permitted.
533 Environment processing is disabled by default and is
535 .Cm PermitUserEnvironment
537 .It Cm expiry-time="timespec"
538 Specifies a time after which the key will not be accepted.
539 The time may be specified as a YYYYMMDD[Z] date or a YYYYMMDDHHMM[SS][Z] time.
540 Dates and times will be interpreted in the system time zone unless suffixed
541 by a Z character, in which case they will be interpreted in the UTC time zone.
542 .It Cm from="pattern-list"
543 Specifies that in addition to public key authentication, either the canonical
544 name of the remote host or its IP address must be present in the
545 comma-separated list of patterns.
548 for more information on patterns.
550 In addition to the wildcard matching that may be applied to hostnames or
553 stanza may match IP addresses using CIDR address/masklen notation.
555 The purpose of this option is to optionally increase security: public key
556 authentication by itself does not trust the network or name servers or
557 anything (but the key); however, if somebody somehow steals the key, the key
558 permits an intruder to log in from anywhere in the world.
559 This additional option makes using a stolen key more difficult (name
560 servers and/or routers would have to be compromised in addition to
562 .It Cm no-agent-forwarding
563 Forbids authentication agent forwarding when this key is used for
565 .It Cm no-port-forwarding
566 Forbids TCP forwarding when this key is used for authentication.
567 Any port forward requests by the client will return an error.
568 This might be used, e.g. in connection with the
572 Prevents tty allocation (a request to allocate a pty will fail).
574 Disables execution of
576 .It Cm no-X11-forwarding
577 Forbids X11 forwarding when this key is used for authentication.
578 Any X11 forward requests by the client will return an error.
579 .It Cm permitlisten="[host:]port"
580 Limit remote port forwarding with the
583 option such that it may only listen on the specified host (optional) and port.
584 IPv6 addresses can be specified by enclosing the address in square brackets.
587 options may be applied separated by commas.
588 Hostnames may include wildcards as described in the PATTERNS section in
590 A port specification of
593 Note that the setting of
595 may further restrict listen addresses.
598 will send a hostname of
600 if a listen host was not specified when the forwarding was requested, and
601 that this name is treated differently to the explicit localhost addresses
605 .It Cm permitopen="host:port"
606 Limit local port forwarding with the
609 option such that it may only connect to the specified host and port.
610 IPv6 addresses can be specified by enclosing the address in square brackets.
613 options may be applied separated by commas.
614 No pattern matching or name lookup is performed on the
615 specified hostnames, they must be literal host names and/or addresses.
616 A port specification of
619 .It Cm port-forwarding
620 Enable port forwarding previously disabled by the
623 .It Cm principals="principals"
626 line, specifies allowed principals for certificate authentication as a
627 comma-separated list.
628 At least one name from the list must appear in the certificate's
629 list of principals for the certificate to be accepted.
630 This option is ignored for keys that are not marked as trusted certificate
635 Permits tty allocation previously disabled by the
638 .It Cm no-touch-required
639 Do not require demonstration of user presence
640 for signatures made using this key.
641 This option only makes sense for the FIDO authenticator algorithms
645 .It Cm verify-required
646 Require that signatures made using this key attest that they verified
647 the user, e.g. via a PIN.
648 This option only makes sense for the FIDO authenticator algorithms
653 Enable all restrictions, i.e. disable port, agent and X11 forwarding,
654 as well as disabling PTY allocation
657 If any future restriction capabilities are added to authorized_keys files,
658 they will be included in this set.
662 device on the server.
663 Without this option, the next available device will be used if
664 the client requests a tunnel.
668 previously disabled by the
671 .It Cm X11-forwarding
672 Permits X11 forwarding previously disabled by the
677 An example authorized_keys file:
678 .Bd -literal -offset 3n
679 # Comments are allowed at start of line. Blank lines are allowed.
680 # Plain key, no restrictions
682 # Forced command, disable PTY and all forwarding
683 restrict,command="dump /home" ssh-rsa ...
684 # Restriction of ssh -L forwarding destinations
685 permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-rsa ...
686 # Restriction of ssh -R forwarding listeners
687 permitlisten="localhost:8080",permitlisten="[::1]:22000" ssh-rsa ...
688 # Configuration for tunnel forwarding
689 tunnel="0",command="sh /etc/netstart tun0" ssh-rsa ...
690 # Override of restriction to allow PTY allocation
691 restrict,pty,command="nethack" ssh-rsa ...
692 # Allow FIDO key without requiring touch
693 no-touch-required sk-ecdsa-sha2-nistp256@openssh.com ...
694 # Require user-verification (e.g. PIN or biometric) for FIDO key
695 verify-required sk-ecdsa-sha2-nistp256@openssh.com ...
696 # Trust CA key, allow touch-less FIDO if requested in certificate
697 cert-authority,no-touch-required,principals="user_a" ssh-rsa ...
699 .Sh SSH_KNOWN_HOSTS FILE FORMAT
701 .Pa /etc/ssh/ssh_known_hosts
703 .Pa ~/.ssh/known_hosts
704 files contain host public keys for all known hosts.
705 The global file should
706 be prepared by the administrator (optional), and the per-user file is
707 maintained automatically: whenever the user connects to an unknown host,
708 its key is added to the per-user file.
710 Each line in these files contains the following fields: marker (optional),
711 hostnames, keytype, base64-encoded key, comment.
712 The fields are separated by spaces.
714 The marker is optional, but if it is present then it must be one of
715 .Dq @cert-authority ,
716 to indicate that the line contains a certification authority (CA) key,
719 to indicate that the key contained on the line is revoked and must not ever
721 Only one marker should be used on a key line.
723 Hostnames is a comma-separated list of patterns
728 wildcards); each pattern in turn is matched against the host name.
731 is authenticating a client, such as when using
732 .Cm HostbasedAuthentication ,
733 this will be the canonical client host name.
736 is authenticating a server, this will be the host name
737 given by the user, the value of the
740 if it was specified, or the canonical server hostname if the
742 .Cm CanonicalizeHostname
745 A pattern may also be preceded by
747 to indicate negation: if the host name matches a negated
748 pattern, it is not accepted (by that line) even if it matched another
750 A hostname or address may optionally be enclosed within
754 brackets then followed by
756 and a non-standard port number.
758 Alternately, hostnames may be stored in a hashed form which hides host names
759 and addresses should the file's contents be disclosed.
760 Hashed hostnames start with a
763 Only one hashed hostname may appear on a single line and none of the above
764 negation or wildcard operators may be applied.
766 The keytype and base64-encoded key are taken directly from the host key; they
767 can be obtained, for example, from
768 .Pa /etc/ssh/ssh_host_rsa_key.pub .
769 The optional comment field continues to the end of the line, and is not used.
773 and empty lines are ignored as comments.
775 When performing host authentication, authentication is accepted if any
776 matching line has the proper key; either one that matches exactly or,
777 if the server has presented a certificate for authentication, the key
778 of the certification authority that signed the certificate.
779 For a key to be trusted as a certification authority, it must use the
781 marker described above.
783 The known hosts file also provides a facility to mark keys as revoked,
784 for example when it is known that the associated private key has been
786 Revoked keys are specified by including the
788 marker at the beginning of the key line, and are never accepted for
789 authentication or as certification authorities, but instead will
790 produce a warning from
792 when they are encountered.
794 It is permissible (but not
795 recommended) to have several lines or different host keys for the same
797 This will inevitably happen when short forms of host names
798 from different domains are put in the file.
800 that the files contain conflicting information; authentication is
801 accepted if valid information can be found from either file.
803 Note that the lines in these files are typically hundreds of characters
804 long, and you definitely don't want to type in the host keys by hand.
805 Rather, generate them by a script,
807 or by taking, for example,
808 .Pa /etc/ssh/ssh_host_rsa_key.pub
809 and adding the host names at the front.
811 also offers some basic automated editing for
812 .Pa ~/.ssh/known_hosts
813 including removing hosts matching a host name and converting all host
814 names to their hashed representations.
816 An example ssh_known_hosts file:
817 .Bd -literal -offset 3n
818 # Comments allowed at start of line
819 cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....=
821 |1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa
824 @revoked * ssh-rsa AAAAB5W...
825 # A CA key, accepted for any host in *.mydomain.com or *.mydomain.org
826 @cert-authority *.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W...
829 .Bl -tag -width Ds -compact
831 This file is used to suppress printing the last login time and
839 It does not suppress printing of the banner specified by
843 This file is used for host-based authentication (see
845 for more information).
846 On some machines this file may need to be
847 world-readable if the user's home directory is on an NFS partition,
851 Additionally, this file must be owned by the user,
852 and must not have write permissions for anyone else.
854 permission for most machines is read/write for the user, and not
855 accessible by others.
858 This file is used in exactly the same way as
860 but allows host-based authentication without permitting login with
864 This directory is the default location for all user-specific configuration
865 and authentication information.
866 There is no general requirement to keep the entire contents of this directory
867 secret, but the recommended permissions are read/write/execute for the user,
868 and not accessible by others.
870 .It Pa ~/.ssh/authorized_keys
871 Lists the public keys (DSA, ECDSA, Ed25519, RSA)
872 that can be used for logging in as this user.
873 The format of this file is described above.
874 The content of the file is not highly sensitive, but the recommended
875 permissions are read/write for the user, and not accessible by others.
879 directory, or the user's home directory are writable
880 by other users, then the file could be modified or replaced by unauthorized
884 will not allow it to be used unless the
886 option has been set to
889 .It Pa ~/.ssh/environment
890 This file is read into the environment at login (if it exists).
891 It can only contain empty lines, comment lines (that start with
893 and assignment lines of the form name=value.
894 The file should be writable
895 only by the user; it need not be readable by anyone else.
896 Environment processing is disabled by default and is
898 .Cm PermitUserEnvironment
901 .It Pa ~/.ssh/known_hosts
902 Contains a list of host keys for all hosts the user has logged into
903 that are not already in the systemwide list of known host keys.
904 The format of this file is described above.
905 This file should be writable only by root/the owner and
906 can, but need not be, world-readable.
909 Contains initialization routines to be run before
910 the user's home directory becomes accessible.
911 This file should be writable only by the user, and need not be
912 readable by anyone else.
914 .It Pa /etc/hosts.allow
915 .It Pa /etc/hosts.deny
916 Access controls that should be enforced by tcp-wrappers are defined here.
917 Further details are described in
920 .It Pa /etc/hosts.equiv
921 This file is for host-based authentication (see
923 It should only be writable by root.
926 Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange"
928 The file format is described in
930 If no usable groups are found in this file then fixed internal groups will
940 refuses to let anyone except root log in.
941 The contents of the file
942 are displayed to anyone trying to log in, and non-root connections are
944 The file should be world-readable.
946 .It Pa /etc/shosts.equiv
947 This file is used in exactly the same way as
949 but allows host-based authentication without permitting login with
952 .It Pa /etc/ssh/ssh_host_ecdsa_key
953 .It Pa /etc/ssh/ssh_host_ed25519_key
954 .It Pa /etc/ssh/ssh_host_rsa_key
955 These files contain the private parts of the host keys.
956 These files should only be owned by root, readable only by root, and not
957 accessible to others.
960 does not start if these files are group/world-accessible.
962 .It Pa /etc/ssh/ssh_host_ecdsa_key.pub
963 .It Pa /etc/ssh/ssh_host_ed25519_key.pub
964 .It Pa /etc/ssh/ssh_host_rsa_key.pub
965 These files contain the public parts of the host keys.
966 These files should be world-readable but writable only by
968 Their contents should match the respective private parts.
970 really used for anything; they are provided for the convenience of
971 the user so their contents can be copied to known hosts files.
972 These files are created using
975 .It Pa /etc/ssh/ssh_known_hosts
976 Systemwide list of known host keys.
977 This file should be prepared by the
978 system administrator to contain the public host keys of all machines in the
980 The format of this file is described above.
981 This file should be writable only by root/the owner and
982 should be world-readable.
984 .It Pa /etc/ssh/sshd_config
985 Contains configuration data for
987 The file format and configuration options are described in
990 .It Pa /etc/ssh/sshrc
993 it can be used to specify
994 machine-specific login-time initializations globally.
995 This file should be writable only by root, and should be world-readable.
1001 during privilege separation in the pre-authentication phase.
1002 The directory should not contain any files and must be owned by root
1003 and not group or world-writable.
1005 .It Pa /var/run/sshd.pid
1006 Contains the process ID of the
1008 listening for connections (if there are several daemons running
1009 concurrently for different ports, this contains the process ID of the one
1011 The content of this file is not sensitive; it can be world-readable.
1022 .Xr hosts_access 5 ,
1029 OpenSSH is a derivative of the original and free
1030 ssh 1.2.12 release by Tatu Ylonen.
1031 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1032 Theo de Raadt and Dug Song
1033 removed many bugs, re-added newer features and
1035 Markus Friedl contributed the support for SSH
1036 protocol versions 1.5 and 2.0.
1037 Niels Provos and Markus Friedl contributed support
1038 for privilege separation.