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1SSHD(8) System Manager's Manual SSHD(8)
2
3NAME
4 sshd M-bM-^@M-^S OpenSSH SSH daemon
5
6SYNOPSIS
7 sshd [-46DdeiqTt] [-C connection_spec] [-c host_certificate_file]
8 [-E log_file] [-f config_file] [-g login_grace_time]
9 [-h host_key_file] [-o option] [-p port] [-u len]
10
11DESCRIPTION
12 sshd (OpenSSH Daemon) is the daemon program for ssh(1). Together these
13 programs replace rlogin and rsh, and provide secure encrypted
14 communications between two untrusted hosts over an insecure network.
15
16 sshd listens for connections from clients. It is normally started at
17 boot from /etc/rc. It forks a new daemon for each incoming connection.
18 The forked daemons handle key exchange, encryption, authentication,
19 command execution, and data exchange.
20
21 sshd can be configured using command-line options or a configuration file
22 (by default sshd_config(5)); command-line options override values
23 specified in the configuration file. sshd rereads its configuration file
24 when it receives a hangup signal, SIGHUP, by executing itself with the
25 name and options it was started with, e.g. /usr/sbin/sshd.
26
27 The options are as follows:
28
29 -4 Forces sshd to use IPv4 addresses only.
30
31 -6 Forces sshd to use IPv6 addresses only.
32
33 -C connection_spec
34 Specify the connection parameters to use for the -T extended test
35 mode. If provided, any Match directives in the configuration
36 file that would apply to the specified user, host, and address
37 will be set before the configuration is written to standard
38 output. The connection parameters are supplied as keyword=value
39 pairs. The keywords are M-bM-^@M-^\userM-bM-^@M-^], M-bM-^@M-^\hostM-bM-^@M-^], M-bM-^@M-^\laddrM-bM-^@M-^], M-bM-^@M-^\lportM-bM-^@M-^], and
40 M-bM-^@M-^\addrM-bM-^@M-^]. All are required and may be supplied in any order,
41 either with multiple -C options or as a comma-separated list.
42
43 -c host_certificate_file
44 Specifies a path to a certificate file to identify sshd during
45 key exchange. The certificate file must match a host key file
46 specified using the -h option or the HostKey configuration
47 directive.
48
49 -D When this option is specified, sshd will not detach and does not
50 become a daemon. This allows easy monitoring of sshd.
51
52 -d Debug mode. The server sends verbose debug output to standard
53 error, and does not put itself in the background. The server
54 also will not fork and will only process one connection. This
55 option is only intended for debugging for the server. Multiple
56 -d options increase the debugging level. Maximum is 3.
57
58 -E log_file
59 Append debug logs to log_file instead of the system log.
60
61 -e Write debug logs to standard error instead of the system log.
62
63 -f config_file
64 Specifies the name of the configuration file. The default is
65 /etc/ssh/sshd_config. sshd refuses to start if there is no
66 configuration file.
67
68 -g login_grace_time
69 Gives the grace time for clients to authenticate themselves
70 (default 120 seconds). If the client fails to authenticate the
71 user within this many seconds, the server disconnects and exits.
72 A value of zero indicates no limit.
73
74 -h host_key_file
75 Specifies a file from which a host key is read. This option must
76 be given if sshd is not run as root (as the normal host key files
77 are normally not readable by anyone but root). The default is
78 /etc/ssh/ssh_host_dsa_key, /etc/ssh/ssh_host_ecdsa_key,
79 /etc/ssh/ssh_host_ed25519_key and /etc/ssh/ssh_host_rsa_key. It
80 is possible to have multiple host key files for the different
81 host key algorithms.
82
83 -i Specifies that sshd is being run from inetd(8).
84
85 -o option
86 Can be used to give options in the format used in the
87 configuration file. This is useful for specifying options for
88 which there is no separate command-line flag. For full details
89 of the options, and their values, see sshd_config(5).
90
91 -p port
92 Specifies the port on which the server listens for connections
93 (default 22). Multiple port options are permitted. Ports
94 specified in the configuration file with the Port option are
95 ignored when a command-line port is specified. Ports specified
96 using the ListenAddress option override command-line ports.
97
98 -q Quiet mode. Nothing is sent to the system log. Normally the
99 beginning, authentication, and termination of each connection is
100 logged.
101
102 -T Extended test mode. Check the validity of the configuration
103 file, output the effective configuration to stdout and then exit.
104 Optionally, Match rules may be applied by specifying the
105 connection parameters using one or more -C options.
106
107 -t Test mode. Only check the validity of the configuration file and
108 sanity of the keys. This is useful for updating sshd reliably as
109 configuration options may change.
110
111 -u len This option is used to specify the size of the field in the utmp
112 structure that holds the remote host name. If the resolved host
113 name is longer than len, the dotted decimal value will be used
114 instead. This allows hosts with very long host names that
115 overflow this field to still be uniquely identified. Specifying
116 -u0 indicates that only dotted decimal addresses should be put
117 into the utmp file. -u0 may also be used to prevent sshd from
118 making DNS requests unless the authentication mechanism or
119 configuration requires it. Authentication mechanisms that may
120 require DNS include HostbasedAuthentication and using a
121 from="pattern-list" option in a key file. Configuration options
122 that require DNS include using a USER@HOST pattern in AllowUsers
123 or DenyUsers.
124
125AUTHENTICATION
126 The OpenSSH SSH daemon supports SSH protocol 2 only. Each host has a
127 host-specific key, used to identify the host. Whenever a client
128 connects, the daemon responds with its public host key. The client
129 compares the host key against its own database to verify that it has not
130 changed. Forward security is provided through a Diffie-Hellman key
131 agreement. This key agreement results in a shared session key. The rest
132 of the session is encrypted using a symmetric cipher, currently 128-bit
133 AES, Blowfish, 3DES, CAST128, Arcfour, 192-bit AES, or 256-bit AES. The
134 client selects the encryption algorithm to use from those offered by the
135 server. Additionally, session integrity is provided through a
136 cryptographic message authentication code (hmac-md5, hmac-sha1, umac-64,
137 umac-128, hmac-ripemd160, hmac-sha2-256 or hmac-sha2-512).
138
139 Finally, the server and the client enter an authentication dialog. The
140 client tries to authenticate itself using host-based authentication,
141 public key authentication, challenge-response authentication, or password
142 authentication.
143
144 Regardless of the authentication type, the account is checked to ensure
145 that it is accessible. An account is not accessible if it is locked,
146 listed in DenyUsers or its group is listed in DenyGroups . The
147 definition of a locked account is system dependant. Some platforms have
148 their own account database (eg AIX) and some modify the passwd field (
149 M-bM-^@M-^X*LK*M-bM-^@M-^Y on Solaris and UnixWare, M-bM-^@M-^X*M-bM-^@M-^Y on HP-UX, containing M-bM-^@M-^XNologinM-bM-^@M-^Y on
150 Tru64, a leading M-bM-^@M-^X*LOCKED*M-bM-^@M-^Y on FreeBSD and a leading M-bM-^@M-^X!M-bM-^@M-^Y on most
151 Linuxes). If there is a requirement to disable password authentication
152 for the account while allowing still public-key, then the passwd field
153 should be set to something other than these values (eg M-bM-^@M-^XNPM-bM-^@M-^Y or M-bM-^@M-^X*NP*M-bM-^@M-^Y ).
154
155 If the client successfully authenticates itself, a dialog for preparing
156 the session is entered. At this time the client may request things like
157 allocating a pseudo-tty, forwarding X11 connections, forwarding TCP
158 connections, or forwarding the authentication agent connection over the
159 secure channel.
160
161 After this, the client either requests a shell or execution of a command.
162 The sides then enter session mode. In this mode, either side may send
163 data at any time, and such data is forwarded to/from the shell or command
164 on the server side, and the user terminal in the client side.
165
166 When the user program terminates and all forwarded X11 and other
167 connections have been closed, the server sends command exit status to the
168 client, and both sides exit.
169
170LOGIN PROCESS
171 When a user successfully logs in, sshd does the following:
172
173 1. If the login is on a tty, and no command has been specified,
174 prints last login time and /etc/motd (unless prevented in the
175 configuration file or by ~/.hushlogin; see the FILES section).
176
177 2. If the login is on a tty, records login time.
178
179 3. Checks /etc/nologin; if it exists, prints contents and quits
180 (unless root).
181
182 4. Changes to run with normal user privileges.
183
184 5. Sets up basic environment.
185
186 6. Reads the file ~/.ssh/environment, if it exists, and users are
187 allowed to change their environment. See the
188 PermitUserEnvironment option in sshd_config(5).
189
190 7. Changes to user's home directory.
191
192 8. If ~/.ssh/rc exists and the sshd_config(5) PermitUserRC option
193 is set, runs it; else if /etc/ssh/sshrc exists, runs it;
194 otherwise runs xauth. The M-bM-^@M-^\rcM-bM-^@M-^] files are given the X11
195 authentication protocol and cookie in standard input. See
196 SSHRC, below.
197
198 9. Runs user's shell or command. All commands are run under the
199 user's login shell as specified in the system password
200 database.
201
202SSHRC
203 If the file ~/.ssh/rc exists, sh(1) runs it after reading the environment
204 files but before starting the user's shell or command. It must not
205 produce any output on stdout; stderr must be used instead. If X11
206 forwarding is in use, it will receive the "proto cookie" pair in its
207 standard input (and DISPLAY in its environment). The script must call
208 xauth(1) because sshd will not run xauth automatically to add X11
209 cookies.
210
211 The primary purpose of this file is to run any initialization routines
212 which may be needed before the user's home directory becomes accessible;
213 AFS is a particular example of such an environment.
214
215 This file will probably contain some initialization code followed by
216 something similar to:
217
218 if read proto cookie && [ -n "$DISPLAY" ]; then
219 if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then
220 # X11UseLocalhost=yes
221 echo add unix:`echo $DISPLAY |
222 cut -c11-` $proto $cookie
223 else
224 # X11UseLocalhost=no
225 echo add $DISPLAY $proto $cookie
226 fi | xauth -q -
227 fi
228
229 If this file does not exist, /etc/ssh/sshrc is run, and if that does not
230 exist either, xauth is used to add the cookie.
231
232AUTHORIZED_KEYS FILE FORMAT
233 AuthorizedKeysFile specifies the files containing public keys for public
234 key authentication; if this option is not specified, the default is
235 ~/.ssh/authorized_keys and ~/.ssh/authorized_keys2. Each line of the
236 file contains one key (empty lines and lines starting with a M-bM-^@M-^X#M-bM-^@M-^Y are
237 ignored as comments). Public keys consist of the following space-
238 separated fields: options, keytype, base64-encoded key, comment. The
239 options field is optional. The keytype is M-bM-^@M-^\ecdsa-sha2-nistp256M-bM-^@M-^],
240 M-bM-^@M-^\ecdsa-sha2-nistp384M-bM-^@M-^], M-bM-^@M-^\ecdsa-sha2-nistp521M-bM-^@M-^], M-bM-^@M-^\ssh-ed25519M-bM-^@M-^], M-bM-^@M-^\ssh-dssM-bM-^@M-^] or
241 M-bM-^@M-^\ssh-rsaM-bM-^@M-^]; the comment field is not used for anything (but may be
242 convenient for the user to identify the key).
243
244 Note that lines in this file can be several hundred bytes long (because
245 of the size of the public key encoding) up to a limit of 8 kilobytes,
246 which permits DSA keys up to 8 kilobits and RSA keys up to 16 kilobits.
247 You don't want to type them in; instead, copy the id_dsa.pub,
248 id_ecdsa.pub, id_ed25519.pub, or the id_rsa.pub file and edit it.
249
250 sshd enforces a minimum RSA key modulus size of 768 bits.
251
252 The options (if present) consist of comma-separated option
253 specifications. No spaces are permitted, except within double quotes.
254 The following option specifications are supported (note that option
255 keywords are case-insensitive):
256
257 agent-forwarding
258 Enable authentication agent forwarding previously disabled by the
259 restrict option.
260
261 cert-authority
262 Specifies that the listed key is a certification authority (CA)
263 that is trusted to validate signed certificates for user
264 authentication.
265
266 Certificates may encode access restrictions similar to these key
267 options. If both certificate restrictions and key options are
268 present, the most restrictive union of the two is applied.
269
270 command="command"
271 Specifies that the command is executed whenever this key is used
272 for authentication. The command supplied by the user (if any) is
273 ignored. The command is run on a pty if the client requests a
274 pty; otherwise it is run without a tty. If an 8-bit clean
275 channel is required, one must not request a pty or should specify
276 no-pty. A quote may be included in the command by quoting it
277 with a backslash.
278
279 This option might be useful to restrict certain public keys to
280 perform just a specific operation. An example might be a key
281 that permits remote backups but nothing else. Note that the
282 client may specify TCP and/or X11 forwarding unless they are
283 explicitly prohibited, e.g. using the restrict key option.
284
285 The command originally supplied by the client is available in the
286 SSH_ORIGINAL_COMMAND environment variable. Note that this option
287 applies to shell, command or subsystem execution. Also note that
288 this command may be superseded by a sshd_config(5) ForceCommand
289 directive.
290
291 If a command is specified and a forced-command is embedded in a
292 certificate used for authentication, then the certificate will be
293 accepted only if the two commands are identical.
294
295 environment="NAME=value"
296 Specifies that the string is to be added to the environment when
297 logging in using this key. Environment variables set this way
298 override other default environment values. Multiple options of
299 this type are permitted. Environment processing is disabled by
300 default and is controlled via the PermitUserEnvironment option.
301
302 from="pattern-list"
303 Specifies that in addition to public key authentication, either
304 the canonical name of the remote host or its IP address must be
305 present in the comma-separated list of patterns. See PATTERNS in
306 ssh_config(5) for more information on patterns.
307
308 In addition to the wildcard matching that may be applied to
309 hostnames or addresses, a from stanza may match IP addresses
310 using CIDR address/masklen notation.
311
312 The purpose of this option is to optionally increase security:
313 public key authentication by itself does not trust the network or
314 name servers or anything (but the key); however, if somebody
315 somehow steals the key, the key permits an intruder to log in
316 from anywhere in the world. This additional option makes using a
317 stolen key more difficult (name servers and/or routers would have
318 to be compromised in addition to just the key).
319
320 no-agent-forwarding
321 Forbids authentication agent forwarding when this key is used for
322 authentication.
323
324 no-port-forwarding
325 Forbids TCP forwarding when this key is used for authentication.
326 Any port forward requests by the client will return an error.
327 This might be used, e.g. in connection with the command option.
328
329 no-pty Prevents tty allocation (a request to allocate a pty will fail).
330
331 no-user-rc
332 Disables execution of ~/.ssh/rc.
333
334 no-X11-forwarding
335 Forbids X11 forwarding when this key is used for authentication.
336 Any X11 forward requests by the client will return an error.
337
338 permitopen="host:port"
339 Limit local port forwarding with ssh(1) -L such that it may only
340 connect to the specified host and port. IPv6 addresses can be
341 specified by enclosing the address in square brackets. Multiple
342 permitopen options may be applied separated by commas. No
343 pattern matching is performed on the specified hostnames, they
344 must be literal domains or addresses. A port specification of *
345 matches any port.
346
347 port-forwarding
348 Enable port forwarding previously disabled by the restrict
349
350 principals="principals"
351 On a cert-authority line, specifies allowed principals for
352 certificate authentication as a comma-separated list. At least
353 one name from the list must appear in the certificate's list of
354 principals for the certificate to be accepted. This option is
355 ignored for keys that are not marked as trusted certificate
356 signers using the cert-authority option.
357
358 pty Permits tty allocation previously disabled by the restrict
359 option.
360
361 restrict
362 Enable all restrictions, i.e. disable port, agent and X11
363 forwarding, as well as disabling PTY allocation and execution of
364 ~/.ssh/rc. If any future restriction capabilities are added to
365 authorized_keys files they will be included in this set.
366
367 tunnel="n"
368 Force a tun(4) device on the server. Without this option, the
369 next available device will be used if the client requests a
370 tunnel.
371
372 user-rc
373 Enables execution of ~/.ssh/rc previously disabled by the
374 restrict option.
375
376 X11-forwarding
377 Permits X11 forwarding previously disabled by the restrict
378 option.
379
380 An example authorized_keys file:
381
382 # Comments allowed at start of line
383 ssh-rsa AAAAB3Nza...LiPk== user@example.net
384 from="*.sales.example.net,!pc.sales.example.net" ssh-rsa
385 AAAAB2...19Q== john@example.net
386 command="dump /home",no-pty,no-port-forwarding ssh-dss
387 AAAAC3...51R== example.net
388 permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-dss
389 AAAAB5...21S==
390 tunnel="0",command="sh /etc/netstart tun0" ssh-rsa AAAA...==
391 jane@example.net
392 restrict,command="uptime" ssh-rsa AAAA1C8...32Tv==
393 user@example.net
394 restrict,pty,command="nethack" ssh-rsa AAAA1f8...IrrC5==
395 user@example.net
396
397SSH_KNOWN_HOSTS FILE FORMAT
398 The /etc/ssh/ssh_known_hosts and ~/.ssh/known_hosts files contain host
399 public keys for all known hosts. The global file should be prepared by
400 the administrator (optional), and the per-user file is maintained
401 automatically: whenever the user connects from an unknown host, its key
402 is added to the per-user file.
403
404 Each line in these files contains the following fields: markers
405 (optional), hostnames, keytype, base64-encoded key, comment. The fields
406 are separated by spaces.
407
408 The marker is optional, but if it is present then it must be one of
409 M-bM-^@M-^\@cert-authorityM-bM-^@M-^], to indicate that the line contains a certification
410 authority (CA) key, or M-bM-^@M-^\@revokedM-bM-^@M-^], to indicate that the key contained on
411 the line is revoked and must not ever be accepted. Only one marker
412 should be used on a key line.
413
414 Hostnames is a comma-separated list of patterns (M-bM-^@M-^X*M-bM-^@M-^Y and M-bM-^@M-^X?M-bM-^@M-^Y act as
415 wildcards); each pattern in turn is matched against the canonical host
416 name (when authenticating a client) or against the user-supplied name
417 (when authenticating a server). A pattern may also be preceded by M-bM-^@M-^X!M-bM-^@M-^Y to
418 indicate negation: if the host name matches a negated pattern, it is not
419 accepted (by that line) even if it matched another pattern on the line.
420 A hostname or address may optionally be enclosed within M-bM-^@M-^X[M-bM-^@M-^Y and M-bM-^@M-^X]M-bM-^@M-^Y
421 brackets then followed by M-bM-^@M-^X:M-bM-^@M-^Y and a non-standard port number.
422
423 Alternately, hostnames may be stored in a hashed form which hides host
424 names and addresses should the file's contents be disclosed. Hashed
425 hostnames start with a M-bM-^@M-^X|M-bM-^@M-^Y character. Only one hashed hostname may
426 appear on a single line and none of the above negation or wildcard
427 operators may be applied.
428
429 The keytype and base64-encoded key are taken directly from the host key;
430 they can be obtained, for example, from /etc/ssh/ssh_host_rsa_key.pub.
431 The optional comment field continues to the end of the line, and is not
432 used.
433
434 Lines starting with M-bM-^@M-^X#M-bM-^@M-^Y and empty lines are ignored as comments.
435
436 When performing host authentication, authentication is accepted if any
437 matching line has the proper key; either one that matches exactly or, if
438 the server has presented a certificate for authentication, the key of the
439 certification authority that signed the certificate. For a key to be
440 trusted as a certification authority, it must use the M-bM-^@M-^\@cert-authorityM-bM-^@M-^]
441 marker described above.
442
443 The known hosts file also provides a facility to mark keys as revoked,
444 for example when it is known that the associated private key has been
445 stolen. Revoked keys are specified by including the M-bM-^@M-^\@revokedM-bM-^@M-^] marker at
446 the beginning of the key line, and are never accepted for authentication
447 or as certification authorities, but instead will produce a warning from
448 ssh(1) when they are encountered.
449
450 It is permissible (but not recommended) to have several lines or
451 different host keys for the same names. This will inevitably happen when
452 short forms of host names from different domains are put in the file. It
453 is possible that the files contain conflicting information;
454 authentication is accepted if valid information can be found from either
455 file.
456
457 Note that the lines in these files are typically hundreds of characters
458 long, and you definitely don't want to type in the host keys by hand.
459 Rather, generate them by a script, ssh-keyscan(1) or by taking, for
460 example, /etc/ssh/ssh_host_rsa_key.pub and adding the host names at the
461 front. ssh-keygen(1) also offers some basic automated editing for
462 ~/.ssh/known_hosts including removing hosts matching a host name and
463 converting all host names to their hashed representations.
464
465 An example ssh_known_hosts file:
466
467 # Comments allowed at start of line
468 closenet,...,192.0.2.53 1024 37 159...93 closenet.example.net
469 cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....=
470 # A hashed hostname
471 |1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa
472 AAAA1234.....=
473 # A revoked key
474 @revoked * ssh-rsa AAAAB5W...
475 # A CA key, accepted for any host in *.mydomain.com or *.mydomain.org
476 @cert-authority *.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W...
477
478FILES
479 ~/.hushlogin
480 This file is used to suppress printing the last login time and
481 /etc/motd, if PrintLastLog and PrintMotd, respectively, are
482 enabled. It does not suppress printing of the banner specified
483 by Banner.
484
485 ~/.rhosts
486 This file is used for host-based authentication (see ssh(1) for
487 more information). On some machines this file may need to be
488 world-readable if the user's home directory is on an NFS
489 partition, because sshd reads it as root. Additionally, this
490 file must be owned by the user, and must not have write
491 permissions for anyone else. The recommended permission for most
492 machines is read/write for the user, and not accessible by
493 others.
494
495 ~/.shosts
496 This file is used in exactly the same way as .rhosts, but allows
497 host-based authentication without permitting login with
498 rlogin/rsh.
499
500 ~/.ssh/
501 This directory is the default location for all user-specific
502 configuration and authentication information. There is no
503 general requirement to keep the entire contents of this directory
504 secret, but the recommended permissions are read/write/execute
505 for the user, and not accessible by others.
506
507 ~/.ssh/authorized_keys
508 Lists the public keys (DSA, ECDSA, Ed25519, RSA) that can be used
509 for logging in as this user. The format of this file is
510 described above. The content of the file is not highly
511 sensitive, but the recommended permissions are read/write for the
512 user, and not accessible by others.
513
514 If this file, the ~/.ssh directory, or the user's home directory
515 are writable by other users, then the file could be modified or
516 replaced by unauthorized users. In this case, sshd will not
517 allow it to be used unless the StrictModes option has been set to
518 M-bM-^@M-^\noM-bM-^@M-^].
519
520 ~/.ssh/environment
521 This file is read into the environment at login (if it exists).
522 It can only contain empty lines, comment lines (that start with
523 M-bM-^@M-^X#M-bM-^@M-^Y), and assignment lines of the form name=value. The file
524 should be writable only by the user; it need not be readable by
525 anyone else. Environment processing is disabled by default and
526 is controlled via the PermitUserEnvironment option.
527
528 ~/.ssh/known_hosts
529 Contains a list of host keys for all hosts the user has logged
530 into that are not already in the systemwide list of known host
531 keys. The format of this file is described above. This file
532 should be writable only by root/the owner and can, but need not
533 be, world-readable.
534
535 ~/.ssh/rc
536 Contains initialization routines to be run before the user's home
537 directory becomes accessible. This file should be writable only
538 by the user, and need not be readable by anyone else.
539
540 /etc/hosts.equiv
541 This file is for host-based authentication (see ssh(1)). It
542 should only be writable by root.
543
544 /etc/moduli
545 Contains Diffie-Hellman groups used for the "Diffie-Hellman Group
546 Exchange" key exchange method. The file format is described in
547 moduli(5). If no usable groups are found in this file then fixed
548 internal groups will be used.
549
550 /etc/motd
551 See motd(5).
552
553 /etc/nologin
554 If this file exists, sshd refuses to let anyone except root log
555 in. The contents of the file are displayed to anyone trying to
556 log in, and non-root connections are refused. The file should be
557 world-readable.
558
559 /etc/shosts.equiv
560 This file is used in exactly the same way as hosts.equiv, but
561 allows host-based authentication without permitting login with
562 rlogin/rsh.
563
564 /etc/ssh/ssh_host_dsa_key
565 /etc/ssh/ssh_host_ecdsa_key
566 /etc/ssh/ssh_host_ed25519_key
567 /etc/ssh/ssh_host_rsa_key
568 These files contain the private parts of the host keys. These
569 files should only be owned by root, readable only by root, and
570 not accessible to others. Note that sshd does not start if these
571 files are group/world-accessible.
572
573 /etc/ssh/ssh_host_dsa_key.pub
574 /etc/ssh/ssh_host_ecdsa_key.pub
575 /etc/ssh/ssh_host_ed25519_key.pub
576 /etc/ssh/ssh_host_rsa_key.pub
577 These files contain the public parts of the host keys. These
578 files should be world-readable but writable only by root. Their
579 contents should match the respective private parts. These files
580 are not really used for anything; they are provided for the
581 convenience of the user so their contents can be copied to known
582 hosts files. These files are created using ssh-keygen(1).
583
584 /etc/ssh/ssh_known_hosts
585 Systemwide list of known host keys. This file should be prepared
586 by the system administrator to contain the public host keys of
587 all machines in the organization. The format of this file is
588 described above. This file should be writable only by root/the
589 owner and should be world-readable.
590
591 /etc/ssh/sshd_config
592 Contains configuration data for sshd. The file format and
593 configuration options are described in sshd_config(5).
594
595 /etc/ssh/sshrc
596 Similar to ~/.ssh/rc, it can be used to specify machine-specific
597 login-time initializations globally. This file should be
598 writable only by root, and should be world-readable.
599
600 /var/empty
601 chroot(2) directory used by sshd during privilege separation in
602 the pre-authentication phase. The directory should not contain
603 any files and must be owned by root and not group or world-
604 writable.
605
606 /var/run/sshd.pid
607 Contains the process ID of the sshd listening for connections (if
608 there are several daemons running concurrently for different
609 ports, this contains the process ID of the one started last).
610 The content of this file is not sensitive; it can be world-
611 readable.
612
613SEE ALSO
614 scp(1), sftp(1), ssh(1), ssh-add(1), ssh-agent(1), ssh-keygen(1),
615 ssh-keyscan(1), chroot(2), login.conf(5), moduli(5), sshd_config(5),
616 inetd(8), sftp-server(8)
617
618AUTHORS
619 OpenSSH is a derivative of the original and free ssh 1.2.12 release by
620 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
621 de Raadt and Dug Song removed many bugs, re-added newer features and
622 created OpenSSH. Markus Friedl contributed the support for SSH protocol
623 versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support
624 for privilege separation.
625
626OpenBSD 6.0 November 30, 2016 OpenBSD 6.0
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-01 01:31:38 +0000