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 1.280 2015/07/03 03:49:45 djm Exp $
38 .Dd $Mdocdate: July 3 2015 $
43 .Nd OpenSSH SSH daemon
49 .Op Fl C Ar connection_spec
50 .Op Fl c Ar host_certificate_file
52 .Op Fl f Ar config_file
53 .Op Fl g Ar login_grace_time
54 .Op Fl h Ar host_key_file
55 .Op Fl k Ar key_gen_time
62 (OpenSSH Daemon) is the daemon program for
64 Together these programs replace rlogin and rsh,
65 and provide secure encrypted communications between two untrusted hosts
66 over an insecure network.
69 listens for connections from clients.
70 It is normally started at boot from
73 daemon for each incoming connection.
74 The forked daemons handle
75 key exchange, encryption, authentication, command execution,
79 can be configured using command-line options or a configuration file
82 command-line options override values specified in the
85 rereads its configuration file when it receives a hangup signal,
87 by executing itself with the name and options it was started with, e.g.\&
90 The options are as follows:
95 to use IPv4 addresses only.
99 to use IPv6 addresses only.
101 Specifies the number of bits in the ephemeral protocol version 1
102 server key (default 1024).
103 .It Fl C Ar connection_spec
104 Specify the connection parameters to use for the
109 directives in the configuration file
110 that would apply to the specified user, host, and address will be set before
111 the configuration is written to standard output.
112 The connection parameters are supplied as keyword=value pairs.
120 All are required and may be supplied in any order, either with multiple
122 options or as a comma-separated list.
123 .It Fl c Ar host_certificate_file
124 Specifies a path to a certificate file to identify
127 The certificate file must match a host key file specified using the
131 configuration directive.
133 When this option is specified,
135 will not detach and does not become a daemon.
136 This allows easy monitoring of
140 The server sends verbose debug output to standard error,
141 and does not put itself in the background.
142 The server also will not fork and will only process one connection.
143 This option is only intended for debugging for the server.
146 options increase the debugging level.
151 instead of the system log.
153 Write debug logs to standard error instead of the system log.
154 .It Fl f Ar config_file
155 Specifies the name of the configuration file.
157 .Pa /etc/ssh/sshd_config .
159 refuses to start if there is no configuration file.
160 .It Fl g Ar login_grace_time
161 Gives the grace time for clients to authenticate themselves (default
163 If the client fails to authenticate the user within
164 this many seconds, the server disconnects and exits.
165 A value of zero indicates no limit.
166 .It Fl h Ar host_key_file
167 Specifies a file from which a host key is read.
168 This option must be given if
170 is not run as root (as the normal
171 host key files are normally not readable by anyone but root).
173 .Pa /etc/ssh/ssh_host_key
174 for protocol version 1, and
175 .Pa /etc/ssh/ssh_host_dsa_key ,
176 .Pa /etc/ssh/ssh_host_ecdsa_key .
177 .Pa /etc/ssh/ssh_host_ed25519_key
179 .Pa /etc/ssh/ssh_host_rsa_key
180 for protocol version 2.
181 It is possible to have multiple host key files for
182 the different protocol versions and host key algorithms.
188 If SSH protocol 1 is enabled,
190 should not normally be run
191 from inetd because it needs to generate the server key before it can
192 respond to the client, and this may take some time.
193 Clients may have to wait too long if the key was regenerated every time.
194 .It Fl k Ar key_gen_time
195 Specifies how often the ephemeral protocol version 1 server key is
196 regenerated (default 3600 seconds, or one hour).
197 The motivation for regenerating the key fairly
198 often is that the key is not stored anywhere, and after about an hour
199 it becomes impossible to recover the key for decrypting intercepted
200 communications even if the machine is cracked into or physically
202 A value of zero indicates that the key will never be regenerated.
204 Can be used to give options in the format used in the configuration file.
205 This is useful for specifying options for which there is no separate
207 For full details of the options, and their values, see
210 Specifies the port on which the server listens for connections
212 Multiple port options are permitted.
213 Ports specified in the configuration file with the
215 option are ignored when a command-line port is specified.
216 Ports specified using the
218 option override command-line ports.
221 Nothing is sent to the system log.
222 Normally the beginning,
223 authentication, and termination of each connection is logged.
226 Check the validity of the configuration file, output the effective configuration
227 to stdout and then exit.
230 rules may be applied by specifying the connection parameters using one or more
235 Only check the validity of the configuration file and sanity of the keys.
236 This is useful for updating
238 reliably as configuration options may change.
240 This option is used to specify the size of the field
243 structure that holds the remote host name.
244 If the resolved host name is longer than
246 the dotted decimal value will be used instead.
247 This allows hosts with very long host names that
248 overflow this field to still be uniquely identified.
251 indicates that only dotted decimal addresses
252 should be put into the
256 may also be used to prevent
258 from making DNS requests unless the authentication
259 mechanism or configuration requires it.
260 Authentication mechanisms that may require DNS include
261 .Cm RhostsRSAAuthentication ,
262 .Cm HostbasedAuthentication ,
264 .Cm from="pattern-list"
265 option in a key file.
266 Configuration options that require DNS include using a
273 The OpenSSH SSH daemon supports SSH protocols 1 and 2.
274 The default is to use protocol 2 only,
275 though this can be changed via the
279 Protocol 2 supports DSA, ECDSA, Ed25519 and RSA keys;
280 protocol 1 only supports RSA keys.
282 each host has a host-specific key,
284 used to identify the host.
286 Forward security for protocol 1 is provided through
287 an additional server key,
289 generated when the server starts.
290 This key is normally regenerated every hour if it has been used, and
291 is never stored on disk.
292 Whenever a client connects, the daemon responds with its public
293 host and server keys.
294 The client compares the
295 RSA host key against its own database to verify that it has not changed.
296 The client then generates a 256-bit random number.
298 random number using both the host key and the server key, and sends
299 the encrypted number to the server.
300 Both sides then use this
301 random number as a session key which is used to encrypt all further
302 communications in the session.
303 The rest of the session is encrypted
304 using a conventional cipher, currently Blowfish or 3DES, with 3DES
305 being used by default.
306 The client selects the encryption algorithm
307 to use from those offered by the server.
310 forward security is provided through a Diffie-Hellman key agreement.
311 This key agreement results in a shared session key.
312 The rest of the session is encrypted using a symmetric cipher, currently
313 128-bit AES, Blowfish, 3DES, CAST128, Arcfour, 192-bit AES, or 256-bit AES.
314 The client selects the encryption algorithm
315 to use from those offered by the server.
316 Additionally, session integrity is provided
317 through a cryptographic message authentication code
318 (hmac-md5, hmac-sha1, umac-64, umac-128, hmac-ripemd160,
319 hmac-sha2-256 or hmac-sha2-512).
321 Finally, the server and the client enter an authentication dialog.
322 The client tries to authenticate itself using
323 host-based authentication,
324 public key authentication,
325 challenge-response authentication,
326 or password authentication.
328 Regardless of the authentication type, the account is checked to
329 ensure that it is accessible. An account is not accessible if it is
332 or its group is listed in
334 \&. The definition of a locked account is system dependant. Some platforms
335 have their own account database (eg AIX) and some modify the passwd field (
337 on Solaris and UnixWare,
344 on FreeBSD and a leading
347 If there is a requirement to disable password authentication
348 for the account while allowing still public-key, then the passwd field
349 should be set to something other than these values (eg
355 If the client successfully authenticates itself, a dialog for
356 preparing the session is entered.
357 At this time the client may request
358 things like allocating a pseudo-tty, forwarding X11 connections,
359 forwarding TCP connections, or forwarding the authentication agent
360 connection over the secure channel.
362 After this, the client either requests a shell or execution of a command.
363 The sides then enter session mode.
364 In this mode, either side may send
365 data at any time, and such data is forwarded to/from the shell or
366 command on the server side, and the user terminal in the client side.
368 When the user program terminates and all forwarded X11 and other
369 connections have been closed, the server sends command exit status to
370 the client, and both sides exit.
372 When a user successfully logs in,
375 .Bl -enum -offset indent
377 If the login is on a tty, and no command has been specified,
378 prints last login time and
380 (unless prevented in the configuration file or by
386 If the login is on a tty, records login time.
390 .Pa /var/run/nologin ;
391 if one exists, it prints the contents and quits
394 Changes to run with normal user privileges.
396 Sets up basic environment.
399 .Pa ~/.ssh/environment ,
400 if it exists, and users are allowed to change their environment.
402 .Cm PermitUserEnvironment
406 Changes to user's home directory.
413 option is set, runs it; else if
420 files are given the X11
421 authentication protocol and cookie in standard input.
426 Runs user's shell or command.
427 All commands are run under the user's login shell as specified in the
428 system password database.
435 runs it after reading the
436 environment files but before starting the user's shell or command.
437 It must not produce any output on stdout; stderr must be used
439 If X11 forwarding is in use, it will receive the "proto cookie" pair in
440 its standard input (and
447 will not run xauth automatically to add X11 cookies.
449 The primary purpose of this file is to run any initialization routines
450 which may be needed before the user's home directory becomes
451 accessible; AFS is a particular example of such an environment.
453 This file will probably contain some initialization code followed by
454 something similar to:
455 .Bd -literal -offset 3n
456 if read proto cookie && [ -n "$DISPLAY" ]; then
457 if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then
458 # X11UseLocalhost=yes
459 echo add unix:`echo $DISPLAY |
460 cut -c11-` $proto $cookie
463 echo add $DISPLAY $proto $cookie
468 If this file does not exist,
471 does not exist either, xauth is used to add the cookie.
472 .Sh AUTHORIZED_KEYS FILE FORMAT
473 .Cm AuthorizedKeysFile
474 specifies the files containing public keys for
475 public key authentication;
476 if none is specified, the default is
477 .Pa ~/.ssh/authorized_keys
479 .Pa ~/.ssh/authorized_keys2 .
480 Each line of the file contains one
481 key (empty lines and lines starting with a
485 Protocol 1 public keys consist of the following space-separated fields:
486 options, bits, exponent, modulus, comment.
487 Protocol 2 public key consist of:
488 options, keytype, base64-encoded key, comment.
489 The options field is optional;
490 its presence is determined by whether the line starts
491 with a number or not (the options field never starts with a number).
492 The bits, exponent, modulus, and comment fields give the RSA key for
493 protocol version 1; the
494 comment field is not used for anything (but may be convenient for the
495 user to identify the key).
496 For protocol version 2 the keytype is
497 .Dq ecdsa-sha2-nistp256 ,
498 .Dq ecdsa-sha2-nistp384 ,
499 .Dq ecdsa-sha2-nistp521 ,
505 Note that lines in this file are usually several hundred bytes long
506 (because of the size of the public key encoding) up to a limit of
507 8 kilobytes, which permits DSA keys up to 8 kilobits and RSA
508 keys up to 16 kilobits.
509 You don't want to type them in; instead, copy the
519 enforces a minimum RSA key modulus size for protocol 1
520 and protocol 2 keys of 768 bits.
522 The options (if present) consist of comma-separated option
524 No spaces are permitted, except within double quotes.
525 The following option specifications are supported (note
526 that option keywords are case-insensitive):
528 .It Cm cert-authority
529 Specifies that the listed key is a certification authority (CA) that is
530 trusted to validate signed certificates for user authentication.
532 Certificates may encode access restrictions similar to these key options.
533 If both certificate restrictions and key options are present, the most
534 restrictive union of the two is applied.
535 .It Cm command="command"
536 Specifies that the command is executed whenever this key is used for
538 The command supplied by the user (if any) is ignored.
539 The command is run on a pty if the client requests a pty;
540 otherwise it is run without a tty.
541 If an 8-bit clean channel is required,
542 one must not request a pty or should specify
544 A quote may be included in the command by quoting it with a backslash.
545 This option might be useful
546 to restrict certain public keys to perform just a specific operation.
547 An example might be a key that permits remote backups but nothing else.
548 Note that the client may specify TCP and/or X11
549 forwarding unless they are explicitly prohibited.
550 The command originally supplied by the client is available in the
551 .Ev SSH_ORIGINAL_COMMAND
552 environment variable.
553 Note that this option applies to shell, command or subsystem execution.
554 Also note that this command may be superseded by either a
557 directive or a command embedded in a certificate.
558 .It Cm environment="NAME=value"
559 Specifies that the string is to be added to the environment when
560 logging in using this key.
561 Environment variables set this way
562 override other default environment values.
563 Multiple options of this type are permitted.
564 Environment processing is disabled by default and is
566 .Cm PermitUserEnvironment
568 This option is automatically disabled if
571 .It Cm from="pattern-list"
572 Specifies that in addition to public key authentication, either the canonical
573 name of the remote host or its IP address must be present in the
574 comma-separated list of patterns.
577 for more information on patterns.
579 In addition to the wildcard matching that may be applied to hostnames or
582 stanza may match IP addresses using CIDR address/masklen notation.
584 The purpose of this option is to optionally increase security: public key
585 authentication by itself does not trust the network or name servers or
586 anything (but the key); however, if somebody somehow steals the key, the key
587 permits an intruder to log in from anywhere in the world.
588 This additional option makes using a stolen key more difficult (name
589 servers and/or routers would have to be compromised in addition to
591 .It Cm no-agent-forwarding
592 Forbids authentication agent forwarding when this key is used for
594 .It Cm no-port-forwarding
595 Forbids TCP forwarding when this key is used for authentication.
596 Any port forward requests by the client will return an error.
597 This might be used, e.g. in connection with the
601 Prevents tty allocation (a request to allocate a pty will fail).
603 Disables execution of
605 .It Cm no-X11-forwarding
606 Forbids X11 forwarding when this key is used for authentication.
607 Any X11 forward requests by the client will return an error.
608 .It Cm permitopen="host:port"
609 Limit local port forwarding with
612 such that it may only connect to the specified host and port.
613 IPv6 addresses can be specified by enclosing the address in square brackets.
616 options may be applied separated by commas.
617 No pattern matching is performed on the specified hostnames,
618 they must be literal domains or addresses.
619 A port specification of
622 .It Cm principals="principals"
625 line, specifies allowed principals for certificate authentication as a
626 comma-separated list.
627 At least one name from the list must appear in the certificate's
628 list of principals for the certificate to be accepted.
629 This option is ignored for keys that are not marked as trusted certificate
636 device on the server.
637 Without this option, the next available device will be used if
638 the client requests a tunnel.
641 An example authorized_keys file:
642 .Bd -literal -offset 3n
643 # Comments allowed at start of line
644 ssh-rsa AAAAB3Nza...LiPk== user@example.net
645 from="*.sales.example.net,!pc.sales.example.net" ssh-rsa
646 AAAAB2...19Q== john@example.net
647 command="dump /home",no-pty,no-port-forwarding ssh-dss
648 AAAAC3...51R== example.net
649 permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-dss
651 tunnel="0",command="sh /etc/netstart tun0" ssh-rsa AAAA...==
654 .Sh SSH_KNOWN_HOSTS FILE FORMAT
656 .Pa /etc/ssh/ssh_known_hosts
658 .Pa ~/.ssh/known_hosts
659 files contain host public keys for all known hosts.
660 The global file should
661 be prepared by the administrator (optional), and the per-user file is
662 maintained automatically: whenever the user connects from an unknown host,
663 its key is added to the per-user file.
665 Each line in these files contains the following fields: markers (optional),
666 hostnames, bits, exponent, modulus, comment.
667 The fields are separated by spaces.
669 The marker is optional, but if it is present then it must be one of
670 .Dq @cert-authority ,
671 to indicate that the line contains a certification authority (CA) key,
674 to indicate that the key contained on the line is revoked and must not ever
676 Only one marker should be used on a key line.
678 Hostnames is a comma-separated list of patterns
683 wildcards); each pattern in turn is matched against the canonical host
684 name (when authenticating a client) or against the user-supplied
685 name (when authenticating a server).
686 A pattern may also be preceded by
688 to indicate negation: if the host name matches a negated
689 pattern, it is not accepted (by that line) even if it matched another
691 A hostname or address may optionally be enclosed within
695 brackets then followed by
697 and a non-standard port number.
699 Alternately, hostnames may be stored in a hashed form which hides host names
700 and addresses should the file's contents be disclosed.
701 Hashed hostnames start with a
704 Only one hashed hostname may appear on a single line and none of the above
705 negation or wildcard operators may be applied.
707 Bits, exponent, and modulus are taken directly from the RSA host key; they
708 can be obtained, for example, from
709 .Pa /etc/ssh/ssh_host_key.pub .
710 The optional comment field continues to the end of the line, and is not used.
714 and empty lines are ignored as comments.
716 When performing host authentication, authentication is accepted if any
717 matching line has the proper key; either one that matches exactly or,
718 if the server has presented a certificate for authentication, the key
719 of the certification authority that signed the certificate.
720 For a key to be trusted as a certification authority, it must use the
722 marker described above.
724 The known hosts file also provides a facility to mark keys as revoked,
725 for example when it is known that the associated private key has been
727 Revoked keys are specified by including the
729 marker at the beginning of the key line, and are never accepted for
730 authentication or as certification authorities, but instead will
731 produce a warning from
733 when they are encountered.
735 It is permissible (but not
736 recommended) to have several lines or different host keys for the same
738 This will inevitably happen when short forms of host names
739 from different domains are put in the file.
741 that the files contain conflicting information; authentication is
742 accepted if valid information can be found from either file.
744 Note that the lines in these files are typically hundreds of characters
745 long, and you definitely don't want to type in the host keys by hand.
746 Rather, generate them by a script,
749 .Pa /etc/ssh/ssh_host_key.pub
750 and adding the host names at the front.
752 also offers some basic automated editing for
753 .Pa ~/.ssh/known_hosts
754 including removing hosts matching a host name and converting all host
755 names to their hashed representations.
757 An example ssh_known_hosts file:
758 .Bd -literal -offset 3n
759 # Comments allowed at start of line
760 closenet,...,192.0.2.53 1024 37 159...93 closenet.example.net
761 cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....=
763 |1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa
766 @revoked * ssh-rsa AAAAB5W...
767 # A CA key, accepted for any host in *.mydomain.com or *.mydomain.org
768 @cert-authority *.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W...
771 .Bl -tag -width Ds -compact
773 This file is used to suppress printing the last login time and
781 It does not suppress printing of the banner specified by
785 This file is used for host-based authentication (see
787 for more information).
788 On some machines this file may need to be
789 world-readable if the user's home directory is on an NFS partition,
793 Additionally, this file must be owned by the user,
794 and must not have write permissions for anyone else.
796 permission for most machines is read/write for the user, and not
797 accessible by others.
800 This file is used in exactly the same way as
802 but allows host-based authentication without permitting login with
806 This directory is the default location for all user-specific configuration
807 and authentication information.
808 There is no general requirement to keep the entire contents of this directory
809 secret, but the recommended permissions are read/write/execute for the user,
810 and not accessible by others.
812 .It Pa ~/.ssh/authorized_keys
813 Lists the public keys (DSA, ECDSA, Ed25519, RSA)
814 that can be used for logging in as this user.
815 The format of this file is described above.
816 The content of the file is not highly sensitive, but the recommended
817 permissions are read/write for the user, and not accessible by others.
821 directory, or the user's home directory are writable
822 by other users, then the file could be modified or replaced by unauthorized
826 will not allow it to be used unless the
828 option has been set to
831 .It Pa ~/.ssh/environment
832 This file is read into the environment at login (if it exists).
833 It can only contain empty lines, comment lines (that start with
835 and assignment lines of the form name=value.
836 The file should be writable
837 only by the user; it need not be readable by anyone else.
838 Environment processing is disabled by default and is
840 .Cm PermitUserEnvironment
843 .It Pa ~/.ssh/known_hosts
844 Contains a list of host keys for all hosts the user has logged into
845 that are not already in the systemwide list of known host keys.
846 The format of this file is described above.
847 This file should be writable only by root/the owner and
848 can, but need not be, world-readable.
851 Contains initialization routines to be run before
852 the user's home directory becomes accessible.
853 This file should be writable only by the user, and need not be
854 readable by anyone else.
856 .It Pa /etc/hosts.allow
857 .It Pa /etc/hosts.deny
858 Access controls that should be enforced by tcp-wrappers are defined here.
859 Further details are described in
862 .It Pa /etc/hosts.equiv
863 This file is for host-based authentication (see
865 It should only be writable by root.
868 Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange".
869 The file format is described in
879 refuses to let anyone except root log in.
880 The contents of the file
881 are displayed to anyone trying to log in, and non-root connections are
883 The file should be world-readable.
885 .It Pa /etc/shosts.equiv
886 This file is used in exactly the same way as
888 but allows host-based authentication without permitting login with
891 .It Pa /etc/ssh/ssh_host_key
892 .It Pa /etc/ssh/ssh_host_dsa_key
893 .It Pa /etc/ssh/ssh_host_ecdsa_key
894 .It Pa /etc/ssh/ssh_host_ed25519_key
895 .It Pa /etc/ssh/ssh_host_rsa_key
896 These files contain the private parts of the host keys.
897 These files should only be owned by root, readable only by root, and not
898 accessible to others.
901 does not start if these files are group/world-accessible.
903 .It Pa /etc/ssh/ssh_host_key.pub
904 .It Pa /etc/ssh/ssh_host_dsa_key.pub
905 .It Pa /etc/ssh/ssh_host_ecdsa_key.pub
906 .It Pa /etc/ssh/ssh_host_ed25519_key.pub
907 .It Pa /etc/ssh/ssh_host_rsa_key.pub
908 These files contain the public parts of the host keys.
909 These files should be world-readable but writable only by
911 Their contents should match the respective private parts.
913 really used for anything; they are provided for the convenience of
914 the user so their contents can be copied to known hosts files.
915 These files are created using
918 .It Pa /etc/ssh/ssh_known_hosts
919 Systemwide list of known host keys.
920 This file should be prepared by the
921 system administrator to contain the public host keys of all machines in the
923 The format of this file is described above.
924 This file should be writable only by root/the owner and
925 should be world-readable.
927 .It Pa /etc/ssh/sshd_config
928 Contains configuration data for
930 The file format and configuration options are described in
933 .It Pa /etc/ssh/sshrc
936 it can be used to specify
937 machine-specific login-time initializations globally.
938 This file should be writable only by root, and should be world-readable.
944 during privilege separation in the pre-authentication phase.
945 The directory should not contain any files and must be owned by root
946 and not group or world-writable.
948 .It Pa /var/run/sshd.pid
949 Contains the process ID of the
951 listening for connections (if there are several daemons running
952 concurrently for different ports, this contains the process ID of the one
954 The content of this file is not sensitive; it can be world-readable.
972 OpenSSH is a derivative of the original and free
973 ssh 1.2.12 release by Tatu Ylonen.
974 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
975 Theo de Raadt and Dug Song
976 removed many bugs, re-added newer features and
978 Markus Friedl contributed the support for SSH
979 protocol versions 1.5 and 2.0.
980 Niels Provos and Markus Friedl contributed support
981 for privilege separation.