sshd.0 revision 204861
1SSHD(8) OpenBSD System Manager's Manual SSHD(8) 2 3NAME 4 sshd - OpenSSH SSH daemon 5 6SYNOPSIS 7 sshd [-46DdeiqTt] [-b bits] [-C connection_spec] 8 [-c host_certificate_file] [-f config_file] [-g login_grace_time] 9 [-h host_key_file] [-k key_gen_time] [-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(1) and rsh(1), and provide secure encrypted com- 14 munications 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, com- 19 mand 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 speci- 23 fied in the configuration file. sshd rereads its configuration file when 24 it receives a hangup signal, SIGHUP, by executing itself with the name 25 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 -b bits 34 Specifies the number of bits in the ephemeral protocol version 1 35 server key (default 1024). 36 37 -C connection_spec 38 Specify the connection parameters to use for the -T extended test 39 mode. If provided, any Match directives in the configuration 40 file that would apply to the specified user, host, and address 41 will be set before the configuration is written to standard out- 42 put. The connection parameters are supplied as keyword=value 43 pairs. The keywords are ``user'', ``host'', and ``addr''. All 44 are required and may be supplied in any order, either with multi- 45 ple -C options or as a comma-separated list. 46 47 -c host_certificate_file 48 Specifies a path to a certificate file to identify sshd during 49 key exchange. The certificate file must match a host key file 50 specified using the -h option or the HostKey configuration direc- 51 tive. 52 53 -D When this option is specified, sshd will not detach and does not 54 become a daemon. This allows easy monitoring of sshd. 55 56 -d Debug mode. The server sends verbose debug output to standard 57 error, and does not put itself in the background. The server al- 58 so will not fork and will only process one connection. This op- 59 tion is only intended for debugging for the server. Multiple -d 60 options increase the debugging level. Maximum is 3. 61 62 -e When this option is specified, sshd will send the output to the 63 standard error instead of the system log. 64 65 -f config_file 66 Specifies the name of the configuration file. The default is 67 /etc/ssh/sshd_config. sshd refuses to start if there is no con- 68 figuration file. 69 70 -g login_grace_time 71 Gives the grace time for clients to authenticate themselves (de- 72 fault 120 seconds). If the client fails to authenticate the user 73 within this many seconds, the server disconnects and exits. A 74 value of zero indicates no limit. 75 76 -h host_key_file 77 Specifies a file from which a host key is read. This option must 78 be given if sshd is not run as root (as the normal host key files 79 are normally not readable by anyone but root). The default is 80 /etc/ssh/ssh_host_key for protocol version 1, and 81 /etc/ssh/ssh_host_rsa_key and /etc/ssh/ssh_host_dsa_key for pro- 82 tocol version 2. It is possible to have multiple host key files 83 for the different protocol versions and host key algorithms. 84 85 -i Specifies that sshd is being run from inetd(8). sshd is normally 86 not run from inetd because it needs to generate the server key 87 before it can respond to the client, and this may take tens of 88 seconds. Clients would have to wait too long if the key was re- 89 generated every time. However, with small key sizes (e.g. 512) 90 using sshd from inetd may be feasible. 91 92 -k key_gen_time 93 Specifies how often the ephemeral protocol version 1 server key 94 is regenerated (default 3600 seconds, or one hour). The motiva- 95 tion for regenerating the key fairly often is that the key is not 96 stored anywhere, and after about an hour it becomes impossible to 97 recover the key for decrypting intercepted communications even if 98 the machine is cracked into or physically seized. A value of ze- 99 ro indicates that the key will never be regenerated. 100 101 -o option 102 Can be used to give options in the format used in the configura- 103 tion file. This is useful for specifying options for which there 104 is no separate command-line flag. For full details of the op- 105 tions, and their values, see sshd_config(5). 106 107 -p port 108 Specifies the port on which the server listens for connections 109 (default 22). Multiple port options are permitted. Ports speci- 110 fied in the configuration file with the Port option are ignored 111 when a command-line port is specified. Ports specified using the 112 ListenAddress option override command-line ports. 113 114 -q Quiet mode. Nothing is sent to the system log. Normally the be- 115 ginning, authentication, and termination of each connection is 116 logged. 117 118 -T Extended test mode. Check the validity of the configuration 119 file, output the effective configuration to stdout and then exit. 120 Optionally, Match rules may be applied by specifying the connec- 121 tion parameters using one or more -C options. 122 123 -t Test mode. Only check the validity of the configuration file and 124 sanity of the keys. This is useful for updating sshd reliably as 125 configuration options may change. 126 127 -u len This option is used to specify the size of the field in the utmp 128 structure that holds the remote host name. If the resolved host 129 name is longer than len, the dotted decimal value will be used 130 instead. This allows hosts with very long host names that over- 131 flow this field to still be uniquely identified. Specifying -u0 132 indicates that only dotted decimal addresses should be put into 133 the utmp file. -u0 may also be used to prevent sshd from making 134 DNS requests unless the authentication mechanism or configuration 135 requires it. Authentication mechanisms that may require DNS in- 136 clude RhostsRSAAuthentication, HostbasedAuthentication, and using 137 a from="pattern-list" option in a key file. Configuration op- 138 tions that require DNS include using a USER@HOST pattern in 139 AllowUsers or DenyUsers. 140 141AUTHENTICATION 142 The OpenSSH SSH daemon supports SSH protocols 1 and 2. The default is to 143 use protocol 2 only, though this can be changed via the Protocol option 144 in sshd_config(5). Protocol 2 supports both RSA and DSA keys; protocol 1 145 only supports RSA keys. For both protocols, each host has a host-specif- 146 ic key, normally 2048 bits, used to identify the host. 147 148 Forward security for protocol 1 is provided through an additional server 149 key, normally 768 bits, generated when the server starts. This key is 150 normally regenerated every hour if it has been used, and is never stored 151 on disk. Whenever a client connects, the daemon responds with its public 152 host and server keys. The client compares the RSA host key against its 153 own database to verify that it has not changed. The client then gener- 154 ates a 256-bit random number. It encrypts this random number using both 155 the host key and the server key, and sends the encrypted number to the 156 server. Both sides then use this random number as a session key which is 157 used to encrypt all further communications in the session. The rest of 158 the session is encrypted using a conventional cipher, currently Blowfish 159 or 3DES, with 3DES being used by default. The client selects the encryp- 160 tion algorithm to use from those offered by the server. 161 162 For protocol 2, forward security is provided through a Diffie-Hellman key 163 agreement. This key agreement results in a shared session key. The rest 164 of the session is encrypted using a symmetric cipher, currently 128-bit 165 AES, Blowfish, 3DES, CAST128, Arcfour, 192-bit AES, or 256-bit AES. The 166 client selects the encryption algorithm to use from those offered by the 167 server. Additionally, session integrity is provided through a crypto- 168 graphic message authentication code (hmac-md5, hmac-sha1, umac-64 or 169 hmac-ripemd160). 170 171 Finally, the server and the client enter an authentication dialog. The 172 client tries to authenticate itself using host-based authentication, pub- 173 lic key authentication, challenge-response authentication, or password 174 authentication. 175 176 Regardless of the authentication type, the account is checked to ensure 177 that it is accessible. An account is not accessible if it is locked, 178 listed in DenyUsers or its group is listed in DenyGroups . The defini- 179 tion of a locked account is system dependant. Some platforms have their 180 own account database (eg AIX) and some modify the passwd field ( `*LK*' 181 on Solaris and UnixWare, `*' on HP-UX, containing `Nologin' on Tru64, a 182 leading `*LOCKED*' on FreeBSD and a leading `!' on most Linuxes). If 183 there is a requirement to disable password authentication for the account 184 while allowing still public-key, then the passwd field should be set to 185 something other than these values (eg `NP' or `*NP*' ). 186 187 If the client successfully authenticates itself, a dialog for preparing 188 the session is entered. At this time the client may request things like 189 allocating a pseudo-tty, forwarding X11 connections, forwarding TCP con- 190 nections, or forwarding the authentication agent connection over the se- 191 cure channel. 192 193 After this, the client either requests a shell or execution of a command. 194 The sides then enter session mode. In this mode, either side may send 195 data at any time, and such data is forwarded to/from the shell or command 196 on the server side, and the user terminal in the client side. 197 198 When the user program terminates and all forwarded X11 and other connec- 199 tions have been closed, the server sends command exit status to the 200 client, and both sides exit. 201 202LOGIN PROCESS 203 When a user successfully logs in, sshd does the following: 204 205 1. If the login is on a tty, and no command has been specified, 206 prints last login time and /etc/motd (unless prevented in the 207 configuration file or by ~/.hushlogin; see the FILES section). 208 209 2. If the login is on a tty, records login time. 210 211 3. Checks /etc/nologin; if it exists, prints contents and quits 212 (unless root). 213 214 4. Changes to run with normal user privileges. 215 216 5. Sets up basic environment. 217 218 6. Reads the file ~/.ssh/environment, if it exists, and users are 219 allowed to change their environment. See the 220 PermitUserEnvironment option in sshd_config(5). 221 222 7. Changes to user's home directory. 223 224 8. If ~/.ssh/rc exists, runs it; else if /etc/ssh/sshrc exists, 225 runs it; otherwise runs xauth. The ``rc'' files are given the 226 X11 authentication protocol and cookie in standard input. See 227 SSHRC, below. 228 229 9. Runs user's shell or command. 230 231SSHRC 232 If the file ~/.ssh/rc exists, sh(1) runs it after reading the environment 233 files but before starting the user's shell or command. It must not pro- 234 duce any output on stdout; stderr must be used instead. If X11 forward- 235 ing is in use, it will receive the "proto cookie" pair in its standard 236 input (and DISPLAY in its environment). The script must call xauth(1) 237 because sshd will not run xauth automatically to add X11 cookies. 238 239 The primary purpose of this file is to run any initialization routines 240 which may be needed before the user's home directory becomes accessible; 241 AFS is a particular example of such an environment. 242 243 This file will probably contain some initialization code followed by 244 something similar to: 245 246 if read proto cookie && [ -n "$DISPLAY" ]; then 247 if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then 248 # X11UseLocalhost=yes 249 echo add unix:`echo $DISPLAY | 250 cut -c11-` $proto $cookie 251 else 252 # X11UseLocalhost=no 253 echo add $DISPLAY $proto $cookie 254 fi | xauth -q - 255 fi 256 257 If this file does not exist, /etc/ssh/sshrc is run, and if that does not 258 exist either, xauth is used to add the cookie. 259 260AUTHORIZED_KEYS FILE FORMAT 261 AuthorizedKeysFile specifies the file containing public keys for public 262 key authentication; if none is specified, the default is 263 ~/.ssh/authorized_keys. Each line of the file contains one key (empty 264 lines and lines starting with a `#' are ignored as comments). Protocol 1 265 public keys consist of the following space-separated fields: options, 266 bits, exponent, modulus, comment. Protocol 2 public key consist of: op- 267 tions, keytype, base64-encoded key, comment. The options field is op- 268 tional; its presence is determined by whether the line starts with a num- 269 ber or not (the options field never starts with a number). The bits, ex- 270 ponent, modulus, and comment fields give the RSA key for protocol version 271 1; the comment field is not used for anything (but may be convenient for 272 the user to identify the key). For protocol version 2 the keytype is 273 ``ssh-dss'' or ``ssh-rsa''. 274 275 Note that lines in this file are usually several hundred bytes long (be- 276 cause of the size of the public key encoding) up to a limit of 8 kilo- 277 bytes, which permits DSA keys up to 8 kilobits and RSA keys up to 16 278 kilobits. You don't want to type them in; instead, copy the 279 identity.pub, id_dsa.pub, or the id_rsa.pub file and edit it. 280 281 sshd enforces a minimum RSA key modulus size for protocol 1 and protocol 282 2 keys of 768 bits. 283 284 The options (if present) consist of comma-separated option specifica- 285 tions. No spaces are permitted, except within double quotes. The fol- 286 lowing option specifications are supported (note that option keywords are 287 case-insensitive): 288 289 cert-authority 290 Specifies that the listed key is a certification authority (CA) 291 that is trusted to validate signed certificates for user authen- 292 tication. 293 294 Certificates may encode access restrictions similar to these key 295 options. If both certificate restrictions and key options are 296 present, the most restrictive union of the two is applied. 297 298 command="command" 299 Specifies that the command is executed whenever this key is used 300 for authentication. The command supplied by the user (if any) is 301 ignored. The command is run on a pty if the client requests a 302 pty; otherwise it is run without a tty. If an 8-bit clean chan- 303 nel is required, one must not request a pty or should specify no- 304 pty. A quote may be included in the command by quoting it with a 305 backslash. This option might be useful to restrict certain pub- 306 lic keys to perform just a specific operation. An example might 307 be a key that permits remote backups but nothing else. Note that 308 the client may specify TCP and/or X11 forwarding unless they are 309 explicitly prohibited. The command originally supplied by the 310 client is available in the SSH_ORIGINAL_COMMAND environment vari- 311 able. Note that this option applies to shell, command or subsys- 312 tem execution. Also note that this command may be superseded by 313 either a sshd_config(5) ForceCommand directive or a command em- 314 bedded in a certificate. 315 316 environment="NAME=value" 317 Specifies that the string is to be added to the environment when 318 logging in using this key. Environment variables set this way 319 override other default environment values. Multiple options of 320 this type are permitted. Environment processing is disabled by 321 default and is controlled via the PermitUserEnvironment option. 322 This option is automatically disabled if UseLogin is enabled. 323 324 from="pattern-list" 325 Specifies that in addition to public key authentication, either 326 the canonical name of the remote host or its IP address must be 327 present in the comma-separated list of patterns. See PATTERNS in 328 ssh_config(5) for more information on patterns. 329 330 In addition to the wildcard matching that may be applied to host- 331 names or addresses, a from stanza may match IP addresses using 332 CIDR address/masklen notation. 333 334 The purpose of this option is to optionally increase security: 335 public key authentication by itself does not trust the network or 336 name servers or anything (but the key); however, if somebody 337 somehow steals the key, the key permits an intruder to log in 338 from anywhere in the world. This additional option makes using a 339 stolen key more difficult (name servers and/or routers would have 340 to be compromised in addition to just the key). 341 342 no-agent-forwarding 343 Forbids authentication agent forwarding when this key is used for 344 authentication. 345 346 no-port-forwarding 347 Forbids TCP forwarding when this key is used for authentication. 348 Any port forward requests by the client will return an error. 349 This might be used, e.g. in connection with the command option. 350 351 no-pty Prevents tty allocation (a request to allocate a pty will fail). 352 353 no-user-rc 354 Disables execution of ~/.ssh/rc. 355 356 no-X11-forwarding 357 Forbids X11 forwarding when this key is used for authentication. 358 Any X11 forward requests by the client will return an error. 359 360 permitopen="host:port" 361 Limit local ``ssh -L'' port forwarding such that it may only con- 362 nect to the specified host and port. IPv6 addresses can be spec- 363 ified with an alternative syntax: host/port. Multiple permitopen 364 options may be applied separated by commas. No pattern matching 365 is performed on the specified hostnames, they must be literal do- 366 mains or addresses. 367 368 tunnel="n" 369 Force a tun(4) device on the server. Without this option, the 370 next available device will be used if the client requests a tun- 371 nel. 372 373 An example authorized_keys file: 374 375 # Comments allowed at start of line 376 ssh-rsa AAAAB3Nza...LiPk== user@example.net 377 from="*.sales.example.net,!pc.sales.example.net" ssh-rsa 378 AAAAB2...19Q== john@example.net 379 command="dump /home",no-pty,no-port-forwarding ssh-dss 380 AAAAC3...51R== example.net 381 permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-dss 382 AAAAB5...21S== 383 tunnel="0",command="sh /etc/netstart tun0" ssh-rsa AAAA...== 384 jane@example.net 385 386SSH_KNOWN_HOSTS FILE FORMAT 387 The /etc/ssh/ssh_known_hosts and ~/.ssh/known_hosts files contain host 388 public keys for all known hosts. The global file should be prepared by 389 the administrator (optional), and the per-user file is maintained auto- 390 matically: whenever the user connects from an unknown host, its key is 391 added to the per-user file. 392 393 Each line in these files contains the following fields: markers (option- 394 al), hostnames, bits, exponent, modulus, comment. The fields are sepa- 395 rated by spaces. 396 397 The marker is optional, but if it is present then it must be one of 398 ``@cert-authority'', to indicate that the line contains a certification 399 authority (CA) key, or ``@revoked'', to indicate that the key contained 400 on the line is revoked and must not ever be accepted. Only one marker 401 should be used on a key line. 402 403 Hostnames is a comma-separated list of patterns (`*' and `?' act as wild- 404 cards); each pattern in turn is matched against the canonical host name 405 (when authenticating a client) or against the user-supplied name (when 406 authenticating a server). A pattern may also be preceded by `!' to indi- 407 cate negation: if the host name matches a negated pattern, it is not ac- 408 cepted (by that line) even if it matched another pattern on the line. A 409 hostname or address may optionally be enclosed within `[' and `]' brack- 410 ets then followed by `:' and a non-standard port number. 411 412 Alternately, hostnames may be stored in a hashed form which hides host 413 names and addresses should the file's contents be disclosed. Hashed 414 hostnames start with a `|' character. Only one hashed hostname may ap- 415 pear on a single line and none of the above negation or wildcard opera- 416 tors may be applied. 417 418 Bits, exponent, and modulus are taken directly from the RSA host key; 419 they can be obtained, for example, from /etc/ssh/ssh_host_key.pub. The 420 optional comment field continues to the end of the line, and is not used. 421 422 Lines starting with `#' and empty lines are ignored as comments. 423 424 When performing host authentication, authentication is accepted if any 425 matching line has the proper key; either one that matches exactly or, if 426 the server has presented a certificate for authentication, the key of the 427 certification authority that signed the certificate. For a key to be 428 trusted as a certification authority, it must use the ``@cert-authority'' 429 marker described above. 430 431 The known hosts file also provides a facility to mark keys as revoked, 432 for example when it is known that the associated private key has been 433 stolen. Revoked keys are specified by including the ``@revoked'' marker 434 at the beginning of the key line, and are never accepted for authentica- 435 tion or as certification authorities, but instead will produce a warning 436 from ssh(1) when they are encountered. 437 438 It is permissible (but not recommended) to have several lines or differ- 439 ent host keys for the same names. This will inevitably happen when short 440 forms of host names from different domains are put in the file. It is 441 possible that the files contain conflicting information; authentication 442 is accepted if valid information can be found from either file. 443 444 Note that the lines in these files are typically hundreds of characters 445 long, and you definitely don't want to type in the host keys by hand. 446 Rather, generate them by a script, ssh-keyscan(1) or by taking 447 /etc/ssh/ssh_host_key.pub and adding the host names at the front. 448 ssh-keygen(1) also offers some basic automated editing for 449 ~/.ssh/known_hosts including removing hosts matching a host name and con- 450 verting all host names to their hashed representations. 451 452 An example ssh_known_hosts file: 453 454 # Comments allowed at start of line 455 closenet,...,192.0.2.53 1024 37 159...93 closenet.example.net 456 cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....= 457 # A hashed hostname 458 |1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa 459 AAAA1234.....= 460 # A revoked key 461 @revoked * ssh-rsa AAAAB5W... 462 # A CA key, accepted for any host in *.mydomain.com or *.mydomain.org 463 @cert-authority *.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W... 464 465FILES 466 ~/.hushlogin 467 This file is used to suppress printing the last login time and 468 /etc/motd, if PrintLastLog and PrintMotd, respectively, are en- 469 abled. It does not suppress printing of the banner specified by 470 Banner. 471 472 ~/.rhosts 473 This file is used for host-based authentication (see ssh(1) for 474 more information). On some machines this file may need to be 475 world-readable if the user's home directory is on an NFS parti- 476 tion, because sshd reads it as root. Additionally, this file 477 must be owned by the user, and must not have write permissions 478 for anyone else. The recommended permission for most machines is 479 read/write for the user, and not accessible by others. 480 481 ~/.shosts 482 This file is used in exactly the same way as .rhosts, but allows 483 host-based authentication without permitting login with 484 rlogin/rsh. 485 486 ~/.ssh/ 487 This directory is the default location for all user-specific con- 488 figuration and authentication information. There is no general 489 requirement to keep the entire contents of this directory secret, 490 but the recommended permissions are read/write/execute for the 491 user, and not accessible by others. 492 493 ~/.ssh/authorized_keys 494 Lists the public keys (RSA/DSA) that can be used for logging in 495 as this user. The format of this file is described above. The 496 content of the file is not highly sensitive, but the recommended 497 permissions are read/write for the user, and not accessible by 498 others. 499 500 If this file, the ~/.ssh directory, or the user's home directory 501 are writable by other users, then the file could be modified or 502 replaced by unauthorized users. In this case, sshd will not al- 503 low it to be used unless the StrictModes option has been set to 504 ``no''. 505 506 ~/.ssh/environment 507 This file is read into the environment at login (if it exists). 508 It can only contain empty lines, comment lines (that start with 509 `#'), and assignment lines of the form name=value. The file 510 should be writable only by the user; it need not be readable by 511 anyone else. Environment processing is disabled by default and 512 is controlled via the PermitUserEnvironment option. 513 514 ~/.ssh/known_hosts 515 Contains a list of host keys for all hosts the user has logged 516 into that are not already in the systemwide list of known host 517 keys. The format of this file is described above. This file 518 should be writable only by root/the owner and can, but need not 519 be, world-readable. 520 521 ~/.ssh/rc 522 Contains initialization routines to be run before the user's home 523 directory becomes accessible. This file should be writable only 524 by the user, and need not be readable by anyone else. 525 526 /etc/hosts.allow 527 /etc/hosts.deny 528 Access controls that should be enforced by tcp-wrappers are de- 529 fined here. Further details are described in hosts_access(5). 530 531 /etc/hosts.equiv 532 This file is for host-based authentication (see ssh(1)). It 533 should only be writable by root. 534 535 /etc/moduli 536 Contains Diffie-Hellman groups used for the "Diffie-Hellman Group 537 Exchange". The file format is described in moduli(5). 538 539 /etc/motd 540 See motd(5). 541 542 /etc/nologin 543 If this file exists, sshd refuses to let anyone except root log 544 in. The contents of the file are displayed to anyone trying to 545 log in, and non-root connections are refused. The file should be 546 world-readable. 547 548 /etc/shosts.equiv 549 This file is used in exactly the same way as hosts.equiv, but al- 550 lows host-based authentication without permitting login with 551 rlogin/rsh. 552 553 /etc/ssh/ssh_host_key 554 /etc/ssh/ssh_host_dsa_key 555 /etc/ssh/ssh_host_rsa_key 556 These three files contain the private parts of the host keys. 557 These files should only be owned by root, readable only by root, 558 and not accessible to others. Note that sshd does not start if 559 these files are group/world-accessible. 560 561 /etc/ssh/ssh_host_key.pub 562 /etc/ssh/ssh_host_dsa_key.pub 563 /etc/ssh/ssh_host_rsa_key.pub 564 These three files contain the public parts of the host keys. 565 These files should be world-readable but writable only by root. 566 Their contents should match the respective private parts. These 567 files are not really used for anything; they are provided for the 568 convenience of the user so their contents can be copied to known 569 hosts files. These files are created using ssh-keygen(1). 570 571 /etc/ssh/ssh_known_hosts 572 Systemwide list of known host keys. This file should be prepared 573 by the system administrator to contain the public host keys of 574 all machines in the organization. The format of this file is de- 575 scribed above. This file should be writable only by root/the 576 owner and should be world-readable. 577 578 /etc/ssh/sshd_config 579 Contains configuration data for sshd. The file format and con- 580 figuration options are described in sshd_config(5). 581 582 /etc/ssh/sshrc 583 Similar to ~/.ssh/rc, it can be used to specify machine-specific 584 login-time initializations globally. This file should be 585 writable only by root, and should be world-readable. 586 587 /var/empty 588 chroot(2) directory used by sshd during privilege separation in 589 the pre-authentication phase. The directory should not contain 590 any files and must be owned by root and not group or world- 591 writable. 592 593 /var/run/sshd.pid 594 Contains the process ID of the sshd listening for connections (if 595 there are several daemons running concurrently for different 596 ports, this contains the process ID of the one started last). 597 The content of this file is not sensitive; it can be world-read- 598 able. 599 600SEE ALSO 601 scp(1), sftp(1), ssh(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), 602 ssh-keyscan(1), chroot(2), hosts_access(5), login.conf(5), moduli(5), 603 sshd_config(5), inetd(8), sftp-server(8) 604 605AUTHORS 606 OpenSSH is a derivative of the original and free ssh 1.2.12 release by 607 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo 608 de Raadt and Dug Song removed many bugs, re-added newer features and cre- 609 ated OpenSSH. Markus Friedl contributed the support for SSH protocol 610 versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support 611 for privilege separation. 612 613CAVEATS 614 System security is not improved unless rshd, rlogind, and rexecd are dis- 615 abled (thus completely disabling rlogin and rsh into the machine). 616 617OpenBSD 4.6 March 5, 2010 10 618