sshd_config.0 revision 197670
1SSHD_CONFIG(5) OpenBSD Programmer's Manual SSHD_CONFIG(5) 2 3NAME 4 sshd_config - OpenSSH SSH daemon configuration file 5 6SYNOPSIS 7 /etc/ssh/sshd_config 8 9DESCRIPTION 10 sshd(8) reads configuration data from /etc/ssh/sshd_config (or the file 11 specified with -f on the command line). The file contains keyword-argu- 12 ment pairs, one per line. Lines starting with `#' and empty lines are 13 interpreted as comments. Arguments may optionally be enclosed in double 14 quotes (") in order to represent arguments containing spaces. 15 16 The possible keywords and their meanings are as follows (note that key- 17 words are case-insensitive and arguments are case-sensitive): 18 19 AcceptEnv 20 Specifies what environment variables sent by the client will be 21 copied into the session's environ(7). See SendEnv in 22 ssh_config(5) for how to configure the client. Note that envi- 23 ronment passing is only supported for protocol 2. Variables are 24 specified by name, which may contain the wildcard characters `*' 25 and `?'. Multiple environment variables may be separated by 26 whitespace or spread across multiple AcceptEnv directives. Be 27 warned that some environment variables could be used to bypass 28 restricted user environments. For this reason, care should be 29 taken in the use of this directive. The default is not to accept 30 any environment variables. 31 32 AddressFamily 33 Specifies which address family should be used by sshd(8). Valid 34 arguments are ``any'', ``inet'' (use IPv4 only), or ``inet6'' 35 (use IPv6 only). The default is ``any''. 36 37 AllowAgentForwarding 38 Specifies whether ssh-agent(1) forwarding is permitted. The de- 39 fault is ``yes''. Note that disabling agent forwarding does not 40 improve security unless users are also denied shell access, as 41 they can always install their own forwarders. 42 43 AllowGroups 44 This keyword can be followed by a list of group name patterns, 45 separated by spaces. If specified, login is allowed only for 46 users whose primary group or supplementary group list matches one 47 of the patterns. Only group names are valid; a numerical group 48 ID is not recognized. By default, login is allowed for all 49 groups. The allow/deny directives are processed in the following 50 order: DenyUsers, AllowUsers, DenyGroups, and finally 51 AllowGroups. 52 53 See PATTERNS in ssh_config(5) for more information on patterns. 54 55 AllowTcpForwarding 56 Specifies whether TCP forwarding is permitted. The default is 57 ``yes''. Note that disabling TCP forwarding does not improve se- 58 curity unless users are also denied shell access, as they can al- 59 ways install their own forwarders. 60 61 AllowUsers 62 This keyword can be followed by a list of user name patterns, 63 separated by spaces. If specified, login is allowed only for us- 64 er names that match one of the patterns. Only user names are 65 valid; a numerical user ID is not recognized. By default, login 66 is allowed for all users. If the pattern takes the form US- 67 ER@HOST then USER and HOST are separately checked, restricting 68 logins to particular users from particular hosts. The allow/deny 69 directives are processed in the following order: DenyUsers, 70 AllowUsers, DenyGroups, and finally AllowGroups. 71 72 See PATTERNS in ssh_config(5) for more information on patterns. 73 74 AuthorizedKeysFile 75 Specifies the file that contains the public keys that can be used 76 for user authentication. AuthorizedKeysFile may contain tokens 77 of the form %T which are substituted during connection setup. 78 The following tokens are defined: %% is replaced by a literal 79 '%', %h is replaced by the home directory of the user being au- 80 thenticated, and %u is replaced by the username of that user. 81 After expansion, AuthorizedKeysFile is taken to be an absolute 82 path or one relative to the user's home directory. The default 83 is ``.ssh/authorized_keys''. 84 85 Banner The contents of the specified file are sent to the remote user 86 before authentication is allowed. If the argument is ``none'' 87 then no banner is displayed. This option is only available for 88 protocol version 2. By default, no banner is displayed. 89 90 ChallengeResponseAuthentication 91 Specifies whether challenge-response authentication is allowed 92 (e.g. via PAM or though authentication styles supported in 93 login.conf(5)) The default is ``yes''. 94 95 ChrootDirectory 96 Specifies a path to chroot(2) to after authentication. This 97 path, and all its components, must be root-owned directories that 98 are not writable by any other user or group. After the chroot, 99 sshd(8) changes the working directory to the user's home directo- 100 ry. 101 102 The path may contain the following tokens that are expanded at 103 runtime once the connecting user has been authenticated: %% is 104 replaced by a literal '%', %h is replaced by the home directory 105 of the user being authenticated, and %u is replaced by the user- 106 name of that user. 107 108 The ChrootDirectory must contain the necessary files and directo- 109 ries to support the user's session. For an interactive session 110 this requires at least a shell, typically sh(1), and basic /dev 111 nodes such as null(4), zero(4), stdin(4), stdout(4), stderr(4), 112 arandom(4) and tty(4) devices. For file transfer sessions using 113 ``sftp'', no additional configuration of the environment is nec- 114 essary if the in-process sftp server is used, though sessions 115 which use logging do require /dev/log inside the chroot directory 116 (see sftp-server(8) for details). 117 118 The default is not to chroot(2). 119 120 Ciphers 121 Specifies the ciphers allowed for protocol version 2. Multiple 122 ciphers must be comma-separated. The supported ciphers are 123 ``3des-cbc'', ``aes128-cbc'', ``aes192-cbc'', ``aes256-cbc'', 124 ``aes128-ctr'', ``aes192-ctr'', ``aes256-ctr'', ``arcfour128'', 125 ``arcfour256'', ``arcfour'', ``blowfish-cbc'', and 126 ``cast128-cbc''. The default is: 127 128 aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128, 129 aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc, 130 aes256-cbc,arcfour 131 132 ClientAliveCountMax 133 Sets the number of client alive messages (see below) which may be 134 sent without sshd(8) receiving any messages back from the client. 135 If this threshold is reached while client alive messages are be- 136 ing sent, sshd will disconnect the client, terminating the ses- 137 sion. It is important to note that the use of client alive mes- 138 sages is very different from TCPKeepAlive (below). The client 139 alive messages are sent through the encrypted channel and there- 140 fore will not be spoofable. The TCP keepalive option enabled by 141 TCPKeepAlive is spoofable. The client alive mechanism is valu- 142 able when the client or server depend on knowing when a connec- 143 tion has become inactive. 144 145 The default value is 3. If ClientAliveInterval (see below) is 146 set to 15, and ClientAliveCountMax is left at the default, unre- 147 sponsive SSH clients will be disconnected after approximately 45 148 seconds. This option applies to protocol version 2 only. 149 150 ClientAliveInterval 151 Sets a timeout interval in seconds after which if no data has 152 been received from the client, sshd(8) will send a message 153 through the encrypted channel to request a response from the 154 client. The default is 0, indicating that these messages will 155 not be sent to the client. This option applies to protocol ver- 156 sion 2 only. 157 158 Compression 159 Specifies whether compression is allowed, or delayed until the 160 user has authenticated successfully. The argument must be 161 ``yes'', ``delayed'', or ``no''. The default is ``delayed''. 162 163 DenyGroups 164 This keyword can be followed by a list of group name patterns, 165 separated by spaces. Login is disallowed for users whose primary 166 group or supplementary group list matches one of the patterns. 167 Only group names are valid; a numerical group ID is not recog- 168 nized. By default, login is allowed for all groups. The al- 169 low/deny directives are processed in the following order: 170 DenyUsers, AllowUsers, DenyGroups, and finally AllowGroups. 171 172 See PATTERNS in ssh_config(5) for more information on patterns. 173 174 DenyUsers 175 This keyword can be followed by a list of user name patterns, 176 separated by spaces. Login is disallowed for user names that 177 match one of the patterns. Only user names are valid; a numeri- 178 cal user ID is not recognized. By default, login is allowed for 179 all users. If the pattern takes the form USER@HOST then USER and 180 HOST are separately checked, restricting logins to particular 181 users from particular hosts. The allow/deny directives are pro- 182 cessed in the following order: DenyUsers, AllowUsers, DenyGroups, 183 and finally AllowGroups. 184 185 See PATTERNS in ssh_config(5) for more information on patterns. 186 187 ForceCommand 188 Forces the execution of the command specified by ForceCommand, 189 ignoring any command supplied by the client and ~/.ssh/rc if pre- 190 sent. The command is invoked by using the user's login shell 191 with the -c option. This applies to shell, command, or subsystem 192 execution. It is most useful inside a Match block. The command 193 originally supplied by the client is available in the 194 SSH_ORIGINAL_COMMAND environment variable. Specifying a command 195 of ``internal-sftp'' will force the use of an in-process sftp 196 server that requires no support files when used with 197 ChrootDirectory. 198 199 GatewayPorts 200 Specifies whether remote hosts are allowed to connect to ports 201 forwarded for the client. By default, sshd(8) binds remote port 202 forwardings to the loopback address. This prevents other remote 203 hosts from connecting to forwarded ports. GatewayPorts can be 204 used to specify that sshd should allow remote port forwardings to 205 bind to non-loopback addresses, thus allowing other hosts to con- 206 nect. The argument may be ``no'' to force remote port forward- 207 ings to be available to the local host only, ``yes'' to force re- 208 mote port forwardings to bind to the wildcard address, or 209 ``clientspecified'' to allow the client to select the address to 210 which the forwarding is bound. The default is ``no''. 211 212 GSSAPIAuthentication 213 Specifies whether user authentication based on GSSAPI is allowed. 214 The default is ``no''. Note that this option applies to protocol 215 version 2 only. 216 217 GSSAPICleanupCredentials 218 Specifies whether to automatically destroy the user's credentials 219 cache on logout. The default is ``yes''. Note that this option 220 applies to protocol version 2 only. 221 222 HostbasedAuthentication 223 Specifies whether rhosts or /etc/hosts.equiv authentication to- 224 gether with successful public key client host authentication is 225 allowed (host-based authentication). This option is similar to 226 RhostsRSAAuthentication and applies to protocol version 2 only. 227 The default is ``no''. 228 229 HostbasedUsesNameFromPacketOnly 230 Specifies whether or not the server will attempt to perform a re- 231 verse name lookup when matching the name in the ~/.shosts, 232 ~/.rhosts, and /etc/hosts.equiv files during 233 HostbasedAuthentication. A setting of ``yes'' means that sshd(8) 234 uses the name supplied by the client rather than attempting to 235 resolve the name from the TCP connection itself. The default is 236 ``no''. 237 238 HostKey 239 Specifies a file containing a private host key used by SSH. The 240 default is /etc/ssh/ssh_host_key for protocol version 1, and 241 /etc/ssh/ssh_host_rsa_key and /etc/ssh/ssh_host_dsa_key for pro- 242 tocol version 2. Note that sshd(8) will refuse to use a file if 243 it is group/world-accessible. It is possible to have multiple 244 host key files. ``rsa1'' keys are used for version 1 and ``dsa'' 245 or ``rsa'' are used for version 2 of the SSH protocol. 246 247 IgnoreRhosts 248 Specifies that .rhosts and .shosts files will not be used in 249 RhostsRSAAuthentication or HostbasedAuthentication. 250 251 /etc/hosts.equiv and /etc/shosts.equiv are still used. The de- 252 fault is ``yes''. 253 254 IgnoreUserKnownHosts 255 Specifies whether sshd(8) should ignore the user's 256 ~/.ssh/known_hosts during RhostsRSAAuthentication or 257 HostbasedAuthentication. The default is ``no''. 258 259 KerberosAuthentication 260 Specifies whether the password provided by the user for 261 PasswordAuthentication will be validated through the Kerberos 262 KDC. To use this option, the server needs a Kerberos servtab 263 which allows the verification of the KDC's identity. The default 264 is ``no''. 265 266 KerberosGetAFSToken 267 If AFS is active and the user has a Kerberos 5 TGT, attempt to 268 acquire an AFS token before accessing the user's home directory. 269 The default is ``no''. 270 271 KerberosOrLocalPasswd 272 If password authentication through Kerberos fails then the pass- 273 word will be validated via any additional local mechanism such as 274 /etc/passwd. The default is ``yes''. 275 276 KerberosTicketCleanup 277 Specifies whether to automatically destroy the user's ticket 278 cache file on logout. The default is ``yes''. 279 280 KeyRegenerationInterval 281 In protocol version 1, the ephemeral server key is automatically 282 regenerated after this many seconds (if it has been used). The 283 purpose of regeneration is to prevent decrypting captured ses- 284 sions by later breaking into the machine and stealing the keys. 285 The key is never stored anywhere. If the value is 0, the key is 286 never regenerated. The default is 3600 (seconds). 287 288 ListenAddress 289 Specifies the local addresses sshd(8) should listen on. The fol- 290 lowing forms may be used: 291 292 ListenAddress host|IPv4_addr|IPv6_addr 293 ListenAddress host|IPv4_addr:port 294 ListenAddress [host|IPv6_addr]:port 295 296 If port is not specified, sshd will listen on the address and all 297 prior Port options specified. The default is to listen on all 298 local addresses. Multiple ListenAddress options are permitted. 299 Additionally, any Port options must precede this option for non- 300 port qualified addresses. 301 302 LoginGraceTime 303 The server disconnects after this time if the user has not suc- 304 cessfully logged in. If the value is 0, there is no time limit. 305 The default is 120 seconds. 306 307 LogLevel 308 Gives the verbosity level that is used when logging messages from 309 sshd(8). The possible values are: QUIET, FATAL, ERROR, INFO, 310 VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO. 311 DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify 312 higher levels of debugging output. Logging with a DEBUG level 313 violates the privacy of users and is not recommended. 314 315 MACs Specifies the available MAC (message authentication code) algo- 316 rithms. The MAC algorithm is used in protocol version 2 for data 317 integrity protection. Multiple algorithms must be comma-separat- 318 ed. The default is: 319 320 hmac-md5,hmac-sha1,umac-64@openssh.com, 321 hmac-ripemd160,hmac-sha1-96,hmac-md5-96 322 323 Match Introduces a conditional block. If all of the criteria on the 324 Match line are satisfied, the keywords on the following lines 325 override those set in the global section of the config file, un- 326 til either another Match line or the end of the file. 327 328 The arguments to Match are one or more criteria-pattern pairs. 329 The available criteria are User, Group, Host, and Address. The 330 match patterns may consist of single entries or comma-separated 331 lists and may use the wildcard and negation operators described 332 in the PATTERNS section of ssh_config(5). 333 334 The patterns in an Address criteria may additionally contain ad- 335 dresses to match in CIDR address/masklen format, e.g. 336 ``192.0.2.0/24'' or ``3ffe:ffff::/32''. Note that the mask 337 length provided must be consistent with the address - it is an 338 error to specify a mask length that is too long for the address 339 or one with bits set in this host portion of the address. For 340 example, ``192.0.2.0/33'' and ``192.0.2.0/8'' respectively. 341 342 Only a subset of keywords may be used on the lines following a 343 Match keyword. Available keywords are AllowAgentForwarding, 344 AllowTcpForwarding, Banner, ChrootDirectory, ForceCommand, 345 GatewayPorts, GSSAPIAuthentication, HostbasedAuthentication, 346 KbdInteractiveAuthentication, KerberosAuthentication, 347 MaxAuthTries, MaxSessions, PasswordAuthentication, 348 PermitEmptyPasswords, PermitOpen, PermitRootLogin, 349 RhostsRSAAuthentication, RSAAuthentication, X11DisplayOffset, 350 X11Forwarding and X11UseLocalHost. 351 352 MaxAuthTries 353 Specifies the maximum number of authentication attempts permitted 354 per connection. Once the number of failures reaches half this 355 value, additional failures are logged. The default is 6. 356 357 MaxSessions 358 Specifies the maximum number of open sessions permitted per net- 359 work connection. The default is 10. 360 361 MaxStartups 362 Specifies the maximum number of concurrent unauthenticated con- 363 nections to the SSH daemon. Additional connections will be 364 dropped until authentication succeeds or the LoginGraceTime ex- 365 pires for a connection. The default is 10. 366 367 Alternatively, random early drop can be enabled by specifying the 368 three colon separated values ``start:rate:full'' (e.g. 369 "10:30:60"). sshd(8) will refuse connection attempts with a 370 probability of ``rate/100'' (30%) if there are currently 371 ``start'' (10) unauthenticated connections. The probability in- 372 creases linearly and all connection attempts are refused if the 373 number of unauthenticated connections reaches ``full'' (60). 374 375 PasswordAuthentication 376 Specifies whether password authentication is allowed. The de- 377 fault is ``yes''. 378 379 PermitEmptyPasswords 380 When password authentication is allowed, it specifies whether the 381 server allows login to accounts with empty password strings. The 382 default is ``no''. 383 384 PermitOpen 385 Specifies the destinations to which TCP port forwarding is per- 386 mitted. The forwarding specification must be one of the follow- 387 ing forms: 388 389 PermitOpen host:port 390 PermitOpen IPv4_addr:port 391 PermitOpen [IPv6_addr]:port 392 393 Multiple forwards may be specified by separating them with 394 whitespace. An argument of ``any'' can be used to remove all re- 395 strictions and permit any forwarding requests. By default all 396 port forwarding requests are permitted. 397 398 PermitRootLogin 399 Specifies whether root can log in using ssh(1). The argument 400 must be ``yes'', ``without-password'', ``forced-commands-only'', 401 or ``no''. The default is ``yes''. 402 403 If this option is set to ``without-password'', password authenti- 404 cation is disabled for root. 405 406 If this option is set to ``forced-commands-only'', root login 407 with public key authentication will be allowed, but only if the 408 command option has been specified (which may be useful for taking 409 remote backups even if root login is normally not allowed). All 410 other authentication methods are disabled for root. 411 412 If this option is set to ``no'', root is not allowed to log in. 413 414 PermitTunnel 415 Specifies whether tun(4) device forwarding is allowed. The argu- 416 ment must be ``yes'', ``point-to-point'' (layer 3), ``ethernet'' 417 (layer 2), or ``no''. Specifying ``yes'' permits both ``point- 418 to-point'' and ``ethernet''. The default is ``no''. 419 420 PermitUserEnvironment 421 Specifies whether ~/.ssh/environment and environment= options in 422 ~/.ssh/authorized_keys are processed by sshd(8). The default is 423 ``no''. Enabling environment processing may enable users to by- 424 pass access restrictions in some configurations using mechanisms 425 such as LD_PRELOAD. 426 427 PidFile 428 Specifies the file that contains the process ID of the SSH dae- 429 mon. The default is /var/run/sshd.pid. 430 431 Port Specifies the port number that sshd(8) listens on. The default 432 is 22. Multiple options of this type are permitted. See also 433 ListenAddress. 434 435 PrintLastLog 436 Specifies whether sshd(8) should print the date and time of the 437 last user login when a user logs in interactively. The default 438 is ``yes''. 439 440 PrintMotd 441 Specifies whether sshd(8) should print /etc/motd when a user logs 442 in interactively. (On some systems it is also printed by the 443 shell, /etc/profile, or equivalent.) The default is ``yes''. 444 445 Protocol 446 Specifies the protocol versions sshd(8) supports. The possible 447 values are `1' and `2'. Multiple versions must be comma-separat- 448 ed. The default is ``2,1''. Note that the order of the protocol 449 list does not indicate preference, because the client selects 450 among multiple protocol versions offered by the server. Specify- 451 ing ``2,1'' is identical to ``1,2''. 452 453 PubkeyAuthentication 454 Specifies whether public key authentication is allowed. The de- 455 fault is ``yes''. Note that this option applies to protocol ver- 456 sion 2 only. 457 458 RhostsRSAAuthentication 459 Specifies whether rhosts or /etc/hosts.equiv authentication to- 460 gether with successful RSA host authentication is allowed. The 461 default is ``no''. This option applies to protocol version 1 on- 462 ly. 463 464 RSAAuthentication 465 Specifies whether pure RSA authentication is allowed. The de- 466 fault is ``yes''. This option applies to protocol version 1 on- 467 ly. 468 469 ServerKeyBits 470 Defines the number of bits in the ephemeral protocol version 1 471 server key. The minimum value is 512, and the default is 1024. 472 473 StrictModes 474 Specifies whether sshd(8) should check file modes and ownership 475 of the user's files and home directory before accepting login. 476 This is normally desirable because novices sometimes accidentally 477 leave their directory or files world-writable. The default is 478 ``yes''. 479 480 Subsystem 481 Configures an external subsystem (e.g. file transfer daemon). 482 Arguments should be a subsystem name and a command (with optional 483 arguments) to execute upon subsystem request. 484 485 The command sftp-server(8) implements the ``sftp'' file transfer 486 subsystem. 487 488 Alternately the name ``internal-sftp'' implements an in-process 489 ``sftp'' server. This may simplify configurations using 490 ChrootDirectory to force a different filesystem root on clients. 491 492 By default no subsystems are defined. Note that this option ap- 493 plies to protocol version 2 only. 494 495 SyslogFacility 496 Gives the facility code that is used when logging messages from 497 sshd(8). The possible values are: DAEMON, USER, AUTH, LOCAL0, 498 LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The de- 499 fault is AUTH. 500 501 TCPKeepAlive 502 Specifies whether the system should send TCP keepalive messages 503 to the other side. If they are sent, death of the connection or 504 crash of one of the machines will be properly noticed. However, 505 this means that connections will die if the route is down tem- 506 porarily, and some people find it annoying. On the other hand, 507 if TCP keepalives are not sent, sessions may hang indefinitely on 508 the server, leaving ``ghost'' users and consuming server re- 509 sources. 510 511 The default is ``yes'' (to send TCP keepalive messages), and the 512 server will notice if the network goes down or the client host 513 crashes. This avoids infinitely hanging sessions. 514 515 To disable TCP keepalive messages, the value should be set to 516 ``no''. 517 518 UseDNS Specifies whether sshd(8) should look up the remote host name and 519 check that the resolved host name for the remote IP address maps 520 back to the very same IP address. The default is ``yes''. 521 522 UseLogin 523 Specifies whether login(1) is used for interactive login ses- 524 sions. The default is ``no''. Note that login(1) is never used 525 for remote command execution. Note also, that if this is en- 526 abled, X11Forwarding will be disabled because login(1) does not 527 know how to handle xauth(1) cookies. If UsePrivilegeSeparation 528 is specified, it will be disabled after authentication. 529 530 UsePAM Enables the Pluggable Authentication Module interface. If set to 531 ``yes'' this will enable PAM authentication using 532 ChallengeResponseAuthentication and PasswordAuthentication in ad- 533 dition to PAM account and session module processing for all au- 534 thentication types. 535 536 Because PAM challenge-response authentication usually serves an 537 equivalent role to password authentication, you should disable 538 either PasswordAuthentication or ChallengeResponseAuthentication. 539 540 If UsePAM is enabled, you will not be able to run sshd(8) as a 541 non-root user. The default is ``no''. 542 543 UsePrivilegeSeparation 544 Specifies whether sshd(8) separates privileges by creating an un- 545 privileged child process to deal with incoming network traffic. 546 After successful authentication, another process will be created 547 that has the privilege of the authenticated user. The goal of 548 privilege separation is to prevent privilege escalation by con- 549 taining any corruption within the unprivileged processes. The 550 default is ``yes''. 551 552 X11DisplayOffset 553 Specifies the first display number available for sshd(8)'s X11 554 forwarding. This prevents sshd from interfering with real X11 555 servers. The default is 10. 556 557 X11Forwarding 558 Specifies whether X11 forwarding is permitted. The argument must 559 be ``yes'' or ``no''. The default is ``no''. 560 561 When X11 forwarding is enabled, there may be additional exposure 562 to the server and to client displays if the sshd(8) proxy display 563 is configured to listen on the wildcard address (see 564 X11UseLocalhost below), though this is not the default. Addi- 565 tionally, the authentication spoofing and authentication data 566 verification and substitution occur on the client side. The se- 567 curity risk of using X11 forwarding is that the client's X11 dis- 568 play server may be exposed to attack when the SSH client requests 569 forwarding (see the warnings for ForwardX11 in ssh_config(5)). A 570 system administrator may have a stance in which they want to pro- 571 tect clients that may expose themselves to attack by unwittingly 572 requesting X11 forwarding, which can warrant a ``no'' setting. 573 574 Note that disabling X11 forwarding does not prevent users from 575 forwarding X11 traffic, as users can always install their own 576 forwarders. X11 forwarding is automatically disabled if UseLogin 577 is enabled. 578 579 X11UseLocalhost 580 Specifies whether sshd(8) should bind the X11 forwarding server 581 to the loopback address or to the wildcard address. By default, 582 sshd binds the forwarding server to the loopback address and sets 583 the hostname part of the DISPLAY environment variable to 584 ``localhost''. This prevents remote hosts from connecting to the 585 proxy display. However, some older X11 clients may not function 586 with this configuration. X11UseLocalhost may be set to ``no'' to 587 specify that the forwarding server should be bound to the wild- 588 card address. The argument must be ``yes'' or ``no''. The de- 589 fault is ``yes''. 590 591 XAuthLocation 592 Specifies the full pathname of the xauth(1) program. The default 593 is /usr/X11R6/bin/xauth. 594 595TIME FORMATS 596 sshd(8) command-line arguments and configuration file options that speci- 597 fy time may be expressed using a sequence of the form: time[qualifier], 598 where time is a positive integer value and qualifier is one of the fol- 599 lowing: 600 601 <none> seconds 602 s | S seconds 603 m | M minutes 604 h | H hours 605 d | D days 606 w | W weeks 607 608 Each member of the sequence is added together to calculate the total time 609 value. 610 611 Time format examples: 612 613 600 600 seconds (10 minutes) 614 10m 10 minutes 615 1h30m 1 hour 30 minutes (90 minutes) 616 617FILES 618 /etc/ssh/sshd_config 619 Contains configuration data for sshd(8). This file should be 620 writable by root only, but it is recommended (though not neces- 621 sary) that it be world-readable. 622 623SEE ALSO 624 sshd(8) 625 626AUTHORS 627 OpenSSH is a derivative of the original and free ssh 1.2.12 release by 628 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo 629 de Raadt and Dug Song removed many bugs, re-added newer features and cre- 630 ated OpenSSH. Markus Friedl contributed the support for SSH protocol 631 versions 1.5 and 2.0. Niels Provos and Markus Friedl contributed support 632 for privilege separation. 633 634OpenBSD 4.6 April 21, 2009 10 635