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 1.321 2022/09/11 06:38:11 jmc Exp $
37 .Dd $Mdocdate: September 11 2022 $
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
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 secrecy 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.
260 The client selects the encryption algorithm
261 to use from those offered by the server.
262 Additionally, session integrity is provided
263 through a cryptographic message authentication code (MAC).
265 Finally, the server and the client enter an authentication dialog.
266 The client tries to authenticate itself using
267 host-based authentication,
268 public key authentication,
269 challenge-response authentication,
270 or password authentication.
272 Regardless of the authentication type, the account is checked to
273 ensure that it is accessible. An account is not accessible if it is
276 or its group is listed in
278 \&. The definition of a locked account is system dependent. Some platforms
279 have their own account database (eg AIX) and some modify the passwd field (
281 on Solaris and UnixWare,
288 on FreeBSD and a leading
291 If there is a requirement to disable password authentication
292 for the account while allowing still public-key, then the passwd field
293 should be set to something other than these values (eg
299 If the client successfully authenticates itself, a dialog for
300 preparing the session is entered.
301 At this time the client may request
302 things like allocating a pseudo-tty, forwarding X11 connections,
303 forwarding TCP connections, or forwarding the authentication agent
304 connection over the secure channel.
306 After this, the client either requests an interactive shell or execution
307 or a non-interactive command, which
309 will execute via the user's shell using its
312 The sides then enter session mode.
313 In this mode, either side may send
314 data at any time, and such data is forwarded to/from the shell or
315 command on the server side, and the user terminal in the client side.
317 When the user program terminates and all forwarded X11 and other
318 connections have been closed, the server sends command exit status to
319 the client, and both sides exit.
321 When a user successfully logs in,
324 .Bl -enum -offset indent
326 If the login is on a tty, and no command has been specified,
327 prints last login time and
329 (unless prevented in the configuration file or by
335 If the login is on a tty, records login time.
339 .Pa /var/run/nologin ;
340 if one exists, it prints the contents and quits
343 Changes to run with normal user privileges.
345 Sets up basic environment.
348 .Pa ~/.ssh/environment ,
349 if it exists, and users are allowed to change their environment.
351 .Cm PermitUserEnvironment
355 Changes to user's home directory.
362 option is set, runs it; else if
369 files are given the X11
370 authentication protocol and cookie in standard input.
375 Runs user's shell or command.
376 All commands are run under the user's login shell as specified in the
377 system password database.
384 runs it after reading the
385 environment files but before starting the user's shell or command.
386 It must not produce any output on stdout; stderr must be used
388 If X11 forwarding is in use, it will receive the "proto cookie" pair in
389 its standard input (and
396 will not run xauth automatically to add X11 cookies.
398 The primary purpose of this file is to run any initialization routines
399 which may be needed before the user's home directory becomes
400 accessible; AFS is a particular example of such an environment.
402 This file will probably contain some initialization code followed by
403 something similar to:
404 .Bd -literal -offset 3n
405 if read proto cookie && [ -n "$DISPLAY" ]; then
406 if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then
407 # X11UseLocalhost=yes
408 echo add unix:`echo $DISPLAY |
409 cut -c11-` $proto $cookie
412 echo add $DISPLAY $proto $cookie
417 If this file does not exist,
420 does not exist either, xauth is used to add the cookie.
421 .Sh AUTHORIZED_KEYS FILE FORMAT
422 .Cm AuthorizedKeysFile
423 specifies the files containing public keys for
424 public key authentication;
425 if this option is not specified, the default is
426 .Pa ~/.ssh/authorized_keys
428 .Pa ~/.ssh/authorized_keys2 .
429 Each line of the file contains one
430 key (empty lines and lines starting with a
434 Public keys consist of the following space-separated fields:
435 options, keytype, base64-encoded key, comment.
436 The options field is optional.
437 The supported key types are:
439 .Bl -item -compact -offset indent
441 sk-ecdsa-sha2-nistp256@openssh.com
449 sk-ssh-ed25519@openssh.com
458 The comment field is not used for anything (but may be convenient for the
459 user to identify the key).
461 Note that lines in this file can be several hundred bytes long
462 (because of the size of the public key encoding) up to a limit of
463 8 kilobytes, which permits RSA keys up to 16 kilobits.
464 You don't want to type them in; instead, copy the
467 .Pa id_ecdsa_sk.pub ,
469 .Pa id_ed25519_sk.pub ,
475 enforces a minimum RSA key modulus size of 1024 bits.
477 The options (if present) consist of comma-separated option
479 No spaces are permitted, except within double quotes.
480 The following option specifications are supported (note
481 that option keywords are case-insensitive):
483 .It Cm agent-forwarding
484 Enable authentication agent forwarding previously disabled by the
487 .It Cm cert-authority
488 Specifies that the listed key is a certification authority (CA) that is
489 trusted to validate signed certificates for user authentication.
491 Certificates may encode access restrictions similar to these key options.
492 If both certificate restrictions and key options are present, the most
493 restrictive union of the two is applied.
494 .It Cm command="command"
495 Specifies that the command is executed whenever this key is used for
497 The command supplied by the user (if any) is ignored.
498 The command is run on a pty if the client requests a pty;
499 otherwise it is run without a tty.
500 If an 8-bit clean channel is required,
501 one must not request a pty or should specify
503 A quote may be included in the command by quoting it with a backslash.
505 This option might be useful
506 to restrict certain public keys to perform just a specific operation.
507 An example might be a key that permits remote backups but nothing else.
508 Note that the client may specify TCP and/or X11
509 forwarding unless they are explicitly prohibited, e.g. using the
513 The command originally supplied by the client is available in the
514 .Ev SSH_ORIGINAL_COMMAND
515 environment variable.
516 Note that this option applies to shell, command or subsystem execution.
517 Also note that this command may be superseded by a
522 If a command is specified and a forced-command is embedded in a certificate
523 used for authentication, then the certificate will be accepted only if the
524 two commands are identical.
525 .It Cm environment="NAME=value"
526 Specifies that the string is to be added to the environment when
527 logging in using this key.
528 Environment variables set this way
529 override other default environment values.
530 Multiple options of this type are permitted.
531 Environment processing is disabled by default and is
533 .Cm PermitUserEnvironment
535 .It Cm expiry-time="timespec"
536 Specifies a time after which the key will not be accepted.
537 The time may be specified as a YYYYMMDD[Z] date or a YYYYMMDDHHMM[SS][Z] time.
538 Dates and times will be interpreted in the system time zone unless suffixed
539 by a Z character, in which case they will be interpreted in the UTC time zone.
540 .It Cm from="pattern-list"
541 Specifies that in addition to public key authentication, either the canonical
542 name of the remote host or its IP address must be present in the
543 comma-separated list of patterns.
546 for more information on patterns.
548 In addition to the wildcard matching that may be applied to hostnames or
551 stanza may match IP addresses using CIDR address/masklen notation.
553 The purpose of this option is to optionally increase security: public key
554 authentication by itself does not trust the network or name servers or
555 anything (but the key); however, if somebody somehow steals the key, the key
556 permits an intruder to log in from anywhere in the world.
557 This additional option makes using a stolen key more difficult (name
558 servers and/or routers would have to be compromised in addition to
560 .It Cm no-agent-forwarding
561 Forbids authentication agent forwarding when this key is used for
563 .It Cm no-port-forwarding
564 Forbids TCP forwarding when this key is used for authentication.
565 Any port forward requests by the client will return an error.
566 This might be used, e.g. in connection with the
570 Prevents tty allocation (a request to allocate a pty will fail).
572 Disables execution of
574 .It Cm no-X11-forwarding
575 Forbids X11 forwarding when this key is used for authentication.
576 Any X11 forward requests by the client will return an error.
577 .It Cm permitlisten="[host:]port"
578 Limit remote port forwarding with the
581 option such that it may only listen on the specified host (optional) and port.
582 IPv6 addresses can be specified by enclosing the address in square brackets.
585 options may be applied separated by commas.
586 Hostnames may include wildcards as described in the PATTERNS section in
588 A port specification of
591 Note that the setting of
593 may further restrict listen addresses.
596 will send a hostname of
598 if a listen host was not specified when the forwarding was requested, and
599 that this name is treated differently to the explicit localhost addresses
603 .It Cm permitopen="host:port"
604 Limit local port forwarding with the
607 option such that it may only connect to the specified host and port.
608 IPv6 addresses can be specified by enclosing the address in square brackets.
611 options may be applied separated by commas.
612 No pattern matching or name lookup is performed on the
613 specified hostnames, they must be literal host names and/or addresses.
614 A port specification of
617 .It Cm port-forwarding
618 Enable port forwarding previously disabled by the
621 .It Cm principals="principals"
624 line, specifies allowed principals for certificate authentication as a
625 comma-separated list.
626 At least one name from the list must appear in the certificate's
627 list of principals for the certificate to be accepted.
628 This option is ignored for keys that are not marked as trusted certificate
633 Permits tty allocation previously disabled by the
636 .It Cm no-touch-required
637 Do not require demonstration of user presence
638 for signatures made using this key.
639 This option only makes sense for the FIDO authenticator algorithms
643 .It Cm verify-required
644 Require that signatures made using this key attest that they verified
645 the user, e.g. via a PIN.
646 This option only makes sense for the FIDO authenticator algorithms
651 Enable all restrictions, i.e. disable port, agent and X11 forwarding,
652 as well as disabling PTY allocation
655 If any future restriction capabilities are added to authorized_keys files,
656 they will be included in this set.
660 device on the server.
661 Without this option, the next available device will be used if
662 the client requests a tunnel.
666 previously disabled by the
669 .It Cm X11-forwarding
670 Permits X11 forwarding previously disabled by the
675 An example authorized_keys file:
676 .Bd -literal -offset 3n
677 # Comments are allowed at start of line. Blank lines are allowed.
678 # Plain key, no restrictions
680 # Forced command, disable PTY and all forwarding
681 restrict,command="dump /home" ssh-rsa ...
682 # Restriction of ssh -L forwarding destinations
683 permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-rsa ...
684 # Restriction of ssh -R forwarding listeners
685 permitlisten="localhost:8080",permitlisten="[::1]:22000" ssh-rsa ...
686 # Configuration for tunnel forwarding
687 tunnel="0",command="sh /etc/netstart tun0" ssh-rsa ...
688 # Override of restriction to allow PTY allocation
689 restrict,pty,command="nethack" ssh-rsa ...
690 # Allow FIDO key without requiring touch
691 no-touch-required sk-ecdsa-sha2-nistp256@openssh.com ...
692 # Require user-verification (e.g. PIN or biometric) for FIDO key
693 verify-required sk-ecdsa-sha2-nistp256@openssh.com ...
694 # Trust CA key, allow touch-less FIDO if requested in certificate
695 cert-authority,no-touch-required,principals="user_a" ssh-rsa ...
697 .Sh SSH_KNOWN_HOSTS FILE FORMAT
699 .Pa /etc/ssh/ssh_known_hosts
701 .Pa ~/.ssh/known_hosts
702 files contain host public keys for all known hosts.
703 The global file should
704 be prepared by the administrator (optional), and the per-user file is
705 maintained automatically: whenever the user connects to an unknown host,
706 its key is added to the per-user file.
708 Each line in these files contains the following fields: marker (optional),
709 hostnames, keytype, base64-encoded key, comment.
710 The fields are separated by spaces.
712 The marker is optional, but if it is present then it must be one of
713 .Dq @cert-authority ,
714 to indicate that the line contains a certification authority (CA) key,
717 to indicate that the key contained on the line is revoked and must not ever
719 Only one marker should be used on a key line.
721 Hostnames is a comma-separated list of patterns
726 wildcards); each pattern in turn is matched against the host name.
729 is authenticating a client, such as when using
730 .Cm HostbasedAuthentication ,
731 this will be the canonical client host name.
734 is authenticating a server, this will be the host name
735 given by the user, the value of the
738 if it was specified, or the canonical server hostname if the
740 .Cm CanonicalizeHostname
743 A pattern may also be preceded by
745 to indicate negation: if the host name matches a negated
746 pattern, it is not accepted (by that line) even if it matched another
748 A hostname or address may optionally be enclosed within
752 brackets then followed by
754 and a non-standard port number.
756 Alternately, hostnames may be stored in a hashed form which hides host names
757 and addresses should the file's contents be disclosed.
758 Hashed hostnames start with a
761 Only one hashed hostname may appear on a single line and none of the above
762 negation or wildcard operators may be applied.
764 The keytype and base64-encoded key are taken directly from the host key; they
765 can be obtained, for example, from
766 .Pa /etc/ssh/ssh_host_rsa_key.pub .
767 The optional comment field continues to the end of the line, and is not used.
771 and empty lines are ignored as comments.
773 When performing host authentication, authentication is accepted if any
774 matching line has the proper key; either one that matches exactly or,
775 if the server has presented a certificate for authentication, the key
776 of the certification authority that signed the certificate.
777 For a key to be trusted as a certification authority, it must use the
779 marker described above.
781 The known hosts file also provides a facility to mark keys as revoked,
782 for example when it is known that the associated private key has been
784 Revoked keys are specified by including the
786 marker at the beginning of the key line, and are never accepted for
787 authentication or as certification authorities, but instead will
788 produce a warning from
790 when they are encountered.
792 It is permissible (but not
793 recommended) to have several lines or different host keys for the same
795 This will inevitably happen when short forms of host names
796 from different domains are put in the file.
798 that the files contain conflicting information; authentication is
799 accepted if valid information can be found from either file.
801 Note that the lines in these files are typically hundreds of characters
802 long, and you definitely don't want to type in the host keys by hand.
803 Rather, generate them by a script,
805 or by taking, for example,
806 .Pa /etc/ssh/ssh_host_rsa_key.pub
807 and adding the host names at the front.
809 also offers some basic automated editing for
810 .Pa ~/.ssh/known_hosts
811 including removing hosts matching a host name and converting all host
812 names to their hashed representations.
814 An example ssh_known_hosts file:
815 .Bd -literal -offset 3n
816 # Comments allowed at start of line
817 cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....=
819 |1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa
822 @revoked * ssh-rsa AAAAB5W...
823 # A CA key, accepted for any host in *.mydomain.com or *.mydomain.org
824 @cert-authority *.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W...
827 .Bl -tag -width Ds -compact
829 This file is used to suppress printing the last login time and
837 It does not suppress printing of the banner specified by
841 This file is used for host-based authentication (see
843 for more information).
844 On some machines this file may need to be
845 world-readable if the user's home directory is on an NFS partition,
849 Additionally, this file must be owned by the user,
850 and must not have write permissions for anyone else.
852 permission for most machines is read/write for the user, and not
853 accessible by others.
856 This file is used in exactly the same way as
858 but allows host-based authentication without permitting login with
862 This directory is the default location for all user-specific configuration
863 and authentication information.
864 There is no general requirement to keep the entire contents of this directory
865 secret, but the recommended permissions are read/write/execute for the user,
866 and not accessible by others.
868 .It Pa ~/.ssh/authorized_keys
869 Lists the public keys (DSA, ECDSA, Ed25519, RSA)
870 that can be used for logging in as this user.
871 The format of this file is described above.
872 The content of the file is not highly sensitive, but the recommended
873 permissions are read/write for the user, and not accessible by others.
877 directory, or the user's home directory are writable
878 by other users, then the file could be modified or replaced by unauthorized
882 will not allow it to be used unless the
884 option has been set to
887 .It Pa ~/.ssh/environment
888 This file is read into the environment at login (if it exists).
889 It can only contain empty lines, comment lines (that start with
891 and assignment lines of the form name=value.
892 The file should be writable
893 only by the user; it need not be readable by anyone else.
894 Environment processing is disabled by default and is
896 .Cm PermitUserEnvironment
899 .It Pa ~/.ssh/known_hosts
900 Contains a list of host keys for all hosts the user has logged into
901 that are not already in the systemwide list of known host keys.
902 The format of this file is described above.
903 This file should be writable only by root/the owner and
904 can, but need not be, world-readable.
907 Contains initialization routines to be run before
908 the user's home directory becomes accessible.
909 This file should be writable only by the user, and need not be
910 readable by anyone else.
912 .It Pa /etc/hosts.allow
913 .It Pa /etc/hosts.deny
914 Access controls that should be enforced by tcp-wrappers are defined here.
915 Further details are described in
918 .It Pa /etc/hosts.equiv
919 This file is for host-based authentication (see
921 It should only be writable by root.
924 Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange"
926 The file format is described in
928 If no usable groups are found in this file then fixed internal groups will
938 refuses to let anyone except root log in.
939 The contents of the file
940 are displayed to anyone trying to log in, and non-root connections are
942 The file should be world-readable.
944 .It Pa /etc/shosts.equiv
945 This file is used in exactly the same way as
947 but allows host-based authentication without permitting login with
950 .It Pa /etc/ssh/ssh_host_ecdsa_key
951 .It Pa /etc/ssh/ssh_host_ed25519_key
952 .It Pa /etc/ssh/ssh_host_rsa_key
953 These files contain the private parts of the host keys.
954 These files should only be owned by root, readable only by root, and not
955 accessible to others.
958 does not start if these files are group/world-accessible.
960 .It Pa /etc/ssh/ssh_host_ecdsa_key.pub
961 .It Pa /etc/ssh/ssh_host_ed25519_key.pub
962 .It Pa /etc/ssh/ssh_host_rsa_key.pub
963 These files contain the public parts of the host keys.
964 These files should be world-readable but writable only by
966 Their contents should match the respective private parts.
968 really used for anything; they are provided for the convenience of
969 the user so their contents can be copied to known hosts files.
970 These files are created using
973 .It Pa /etc/ssh/ssh_known_hosts
974 Systemwide list of known host keys.
975 This file should be prepared by the
976 system administrator to contain the public host keys of all machines in the
978 The format of this file is described above.
979 This file should be writable only by root/the owner and
980 should be world-readable.
982 .It Pa /etc/ssh/sshd_config
983 Contains configuration data for
985 The file format and configuration options are described in
988 .It Pa /etc/ssh/sshrc
991 it can be used to specify
992 machine-specific login-time initializations globally.
993 This file should be writable only by root, and should be world-readable.
999 during privilege separation in the pre-authentication phase.
1000 The directory should not contain any files and must be owned by root
1001 and not group or world-writable.
1003 .It Pa /var/run/sshd.pid
1004 Contains the process ID of the
1006 listening for connections (if there are several daemons running
1007 concurrently for different ports, this contains the process ID of the one
1009 The content of this file is not sensitive; it can be world-readable.
1020 .Xr hosts_access 5 ,
1027 OpenSSH is a derivative of the original and free
1028 ssh 1.2.12 release by Tatu Ylonen.
1029 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1030 Theo de Raadt and Dug Song
1031 removed many bugs, re-added newer features and
1033 Markus Friedl contributed the support for SSH
1034 protocol versions 1.5 and 2.0.
1035 Niels Provos and Markus Friedl contributed support
1036 for privilege separation.