1 SSH_CONFIG(5) File Formats Manual SSH_CONFIG(5) 2 3 NAME 4 ssh_config M-bM-^@M-^S OpenSSH SSH client configuration files 5 6 SYNOPSIS 7 ~/.ssh/config 8 /etc/ssh/ssh_config 9 10 DESCRIPTION 11 ssh(1) obtains configuration data from the following sources in the 12 following order: 13 14 1. command-line options 15 2. user's configuration file (~/.ssh/config) 16 3. system-wide configuration file (/etc/ssh/ssh_config) 17 18 For each parameter, the first obtained value will be used. The 19 configuration files contain sections separated by M-bM-^@M-^\HostM-bM-^@M-^] specifications, 20 and that section is only applied for hosts that match one of the patterns 21 given in the specification. The matched host name is usually the one 22 given on the command line (see the CanonicalizeHostname option for 23 exceptions.) 24 25 Since the first obtained value for each parameter is used, more host- 26 specific declarations should be given near the beginning of the file, and 27 general defaults at the end. 28 29 The configuration file has the following format: 30 31 Empty lines and lines starting with M-bM-^@M-^X#M-bM-^@M-^Y are comments. Otherwise a line 32 is of the format M-bM-^@M-^\keyword argumentsM-bM-^@M-^]. Configuration options may be 33 separated by whitespace or optional whitespace and exactly one M-bM-^@M-^X=M-bM-^@M-^Y; the 34 latter format is useful to avoid the need to quote whitespace when 35 specifying configuration options using the ssh, scp, and sftp -o option. 36 Arguments may optionally be enclosed in double quotes (") in order to 37 represent arguments containing spaces. 38 39 The possible keywords and their meanings are as follows (note that 40 keywords are case-insensitive and arguments are case-sensitive): 41 42 Host Restricts the following declarations (up to the next Host or 43 Match keyword) to be only for those hosts that match one of the 44 patterns given after the keyword. If more than one pattern is 45 provided, they should be separated by whitespace. A single M-bM-^@M-^X*M-bM-^@M-^Y 46 as a pattern can be used to provide global defaults for all 47 hosts. The host is usually the hostname argument given on the 48 command line (see the CanonicalizeHostname option for 49 exceptions.) 50 51 A pattern entry may be negated by prefixing it with an 52 exclamation mark (M-bM-^@M-^X!M-bM-^@M-^Y). If a negated entry is matched, then the 53 Host entry is ignored, regardless of whether any other patterns 54 on the line match. Negated matches are therefore useful to 55 provide exceptions for wildcard matches. 56 57 See PATTERNS for more information on patterns. 58 59 Match Restricts the following declarations (up to the next Host or 60 Match keyword) to be used only when the conditions following the 61 Match keyword are satisfied. Match conditions are specified 62 using one or more critera or the single token all which always 63 matches. The available criteria keywords are: canonical, exec, 64 host, originalhost, user, and localuser. The all criteria must 65 appear alone or immediately after canonical. Other criteria may 66 be combined arbitrarily. All criteria but all and canonical 67 require an argument. Criteria may be negated by prepending an 68 exclamation mark (M-bM-^@M-^X!M-bM-^@M-^Y). 69 70 The canonical keywork matches only when the configuration file is 71 being re-parsed after hostname canonicalization (see the 72 CanonicalizeHostname option.) This may be useful to specify 73 conditions that work with canonical host names only. The exec 74 keyword executes the specified command under the user's shell. 75 If the command returns a zero exit status then the condition is 76 considered true. Commands containing whitespace characters must 77 be quoted. The following character sequences in the command will 78 be expanded prior to execution: M-bM-^@M-^X%LM-bM-^@M-^Y will be substituted by the 79 first component of the local host name, M-bM-^@M-^X%lM-bM-^@M-^Y will be substituted 80 by the local host name (including any domain name), M-bM-^@M-^X%hM-bM-^@M-^Y will be 81 substituted by the target host name, M-bM-^@M-^X%nM-bM-^@M-^Y will be substituted by 82 the original target host name specified on the command-line, M-bM-^@M-^X%pM-bM-^@M-^Y 83 the destination port, M-bM-^@M-^X%rM-bM-^@M-^Y by the remote login username, and M-bM-^@M-^X%uM-bM-^@M-^Y 84 by the username of the user running ssh(1). 85 86 The other keywords' criteria must be single entries or comma- 87 separated lists and may use the wildcard and negation operators 88 described in the PATTERNS section. The criteria for the host 89 keyword are matched against the target hostname, after any 90 substitution by the Hostname or CanonicalizeHostname options. 91 The originalhost keyword matches against the hostname as it was 92 specified on the command-line. The user keyword matches against 93 the target username on the remote host. The localuser keyword 94 matches against the name of the local user running ssh(1) (this 95 keyword may be useful in system-wide ssh_config files). 96 97 AddressFamily 98 Specifies which address family to use when connecting. Valid 99 arguments are M-bM-^@M-^\anyM-bM-^@M-^], M-bM-^@M-^\inetM-bM-^@M-^] (use IPv4 only), or M-bM-^@M-^\inet6M-bM-^@M-^] (use IPv6 100 only). 101 102 BatchMode 103 If set to M-bM-^@M-^\yesM-bM-^@M-^], passphrase/password querying will be disabled. 104 This option is useful in scripts and other batch jobs where no 105 user is present to supply the password. The argument must be 106 M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is M-bM-^@M-^\noM-bM-^@M-^]. 107 108 BindAddress 109 Use the specified address on the local machine as the source 110 address of the connection. Only useful on systems with more than 111 one address. Note that this option does not work if 112 UsePrivilegedPort is set to M-bM-^@M-^\yesM-bM-^@M-^]. 113 114 CanonicalDomains 115 When CanonicalizeHostname is enabled, this option specifies the 116 list of domain suffixes in which to search for the specified 117 destination host. 118 119 CanonicalizeFallbackLocal 120 Specifies whether to fail with an error when hostname 121 canonicalization fails. The default, M-bM-^@M-^\yesM-bM-^@M-^], will attempt to look 122 up the unqualified hostname using the system resolver's search 123 rules. A value of M-bM-^@M-^\noM-bM-^@M-^] will cause ssh(1) to fail instantly if 124 CanonicalizeHostname is enabled and the target hostname cannot be 125 found in any of the domains specified by CanonicalDomains. 126 127 CanonicalizeHostname 128 Controls whether explicit hostname canonicalization is performed. 129 The default, M-bM-^@M-^\noM-bM-^@M-^], is not to perform any name rewriting and let 130 the system resolver handle all hostname lookups. If set to M-bM-^@M-^\yesM-bM-^@M-^] 131 then, for connections that do not use a ProxyCommand, ssh(1) will 132 attempt to canonicalize the hostname specified on the command 133 line using the CanonicalDomains suffixes and 134 CanonicalizePermittedCNAMEs rules. If CanonicalizeHostname is 135 set to M-bM-^@M-^\alwaysM-bM-^@M-^], then canonicalization is applied to proxied 136 connections too. 137 138 If this option is enabled, then the configuration files are 139 processed again using the new target name to pick up any new 140 configuration in matching Host and Match stanzas. 141 142 CanonicalizeMaxDots 143 Specifies the maximum number of dot characters in a hostname 144 before canonicalization is disabled. The default, M-bM-^@M-^\1M-bM-^@M-^], allows a 145 single dot (i.e. hostname.subdomain). 146 147 CanonicalizePermittedCNAMEs 148 Specifies rules to determine whether CNAMEs should be followed 149 when canonicalizing hostnames. The rules consist of one or more 150 arguments of source_domain_list:target_domain_list, where 151 source_domain_list is a pattern-list of domains that may follow 152 CNAMEs in canonicalization, and target_domain_list is a pattern- 153 list of domains that they may resolve to. 154 155 For example, M-bM-^@M-^\*.a.example.com:*.b.example.com,*.c.example.comM-bM-^@M-^] 156 will allow hostnames matching M-bM-^@M-^\*.a.example.comM-bM-^@M-^] to be 157 canonicalized to names in the M-bM-^@M-^\*.b.example.comM-bM-^@M-^] or 158 M-bM-^@M-^\*.c.example.comM-bM-^@M-^] domains. 159 160 ChallengeResponseAuthentication 161 Specifies whether to use challenge-response authentication. The 162 argument to this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is 163 M-bM-^@M-^\yesM-bM-^@M-^]. 164 165 CheckHostIP 166 If this flag is set to M-bM-^@M-^\yesM-bM-^@M-^], ssh(1) will additionally check the 167 host IP address in the known_hosts file. This allows ssh to 168 detect if a host key changed due to DNS spoofing. If the option 169 is set to M-bM-^@M-^\noM-bM-^@M-^], the check will not be executed. The default is 170 M-bM-^@M-^\yesM-bM-^@M-^]. 171 172 Cipher Specifies the cipher to use for encrypting the session in 173 protocol version 1. Currently, M-bM-^@M-^\blowfishM-bM-^@M-^], M-bM-^@M-^\3desM-bM-^@M-^], and M-bM-^@M-^\desM-bM-^@M-^] are 174 supported. des is only supported in the ssh(1) client for 175 interoperability with legacy protocol 1 implementations that do 176 not support the 3des cipher. Its use is strongly discouraged due 177 to cryptographic weaknesses. The default is M-bM-^@M-^\3desM-bM-^@M-^]. 178 179 Ciphers 180 Specifies the ciphers allowed for protocol version 2 in order of 181 preference. Multiple ciphers must be comma-separated. The 182 supported ciphers are: 183 184 3des-cbc 185 aes128-cbc 186 aes192-cbc 187 aes256-cbc 188 aes128-ctr 189 aes192-ctr 190 aes256-ctr 191 aes128-gcm (a] openssh.com 192 aes256-gcm (a] openssh.com 193 arcfour 194 arcfour128 195 arcfour256 196 blowfish-cbc 197 cast128-cbc 198 chacha20-poly1305 (a] openssh.com 199 200 The default is: 201 202 aes128-ctr,aes192-ctr,aes256-ctr, 203 aes128-gcm (a] openssh.com,aes256-gcm (a] openssh.com, 204 chacha20-poly1305 (a] openssh.com, 205 arcfour256,arcfour128, 206 aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc, 207 aes192-cbc,aes256-cbc,arcfour 208 209 The list of available ciphers may also be obtained using the -Q 210 option of ssh(1) with an argument of M-bM-^@M-^\cipherM-bM-^@M-^]. 211 212 ClearAllForwardings 213 Specifies that all local, remote, and dynamic port forwardings 214 specified in the configuration files or on the command line be 215 cleared. This option is primarily useful when used from the 216 ssh(1) command line to clear port forwardings set in 217 configuration files, and is automatically set by scp(1) and 218 sftp(1). The argument must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is 219 M-bM-^@M-^\noM-bM-^@M-^]. 220 221 Compression 222 Specifies whether to use compression. The argument must be M-bM-^@M-^\yesM-bM-^@M-^] 223 or M-bM-^@M-^\noM-bM-^@M-^]. The default is M-bM-^@M-^\noM-bM-^@M-^]. 224 225 CompressionLevel 226 Specifies the compression level to use if compression is enabled. 227 The argument must be an integer from 1 (fast) to 9 (slow, best). 228 The default level is 6, which is good for most applications. The 229 meaning of the values is the same as in gzip(1). Note that this 230 option applies to protocol version 1 only. 231 232 ConnectionAttempts 233 Specifies the number of tries (one per second) to make before 234 exiting. The argument must be an integer. This may be useful in 235 scripts if the connection sometimes fails. The default is 1. 236 237 ConnectTimeout 238 Specifies the timeout (in seconds) used when connecting to the 239 SSH server, instead of using the default system TCP timeout. 240 This value is used only when the target is down or really 241 unreachable, not when it refuses the connection. 242 243 ControlMaster 244 Enables the sharing of multiple sessions over a single network 245 connection. When set to M-bM-^@M-^\yesM-bM-^@M-^], ssh(1) will listen for 246 connections on a control socket specified using the ControlPath 247 argument. Additional sessions can connect to this socket using 248 the same ControlPath with ControlMaster set to M-bM-^@M-^\noM-bM-^@M-^] (the 249 default). These sessions will try to reuse the master instance's 250 network connection rather than initiating new ones, but will fall 251 back to connecting normally if the control socket does not exist, 252 or is not listening. 253 254 Setting this to M-bM-^@M-^\askM-bM-^@M-^] will cause ssh to listen for control 255 connections, but require confirmation using the SSH_ASKPASS 256 program before they are accepted (see ssh-add(1) for details). 257 If the ControlPath cannot be opened, ssh will continue without 258 connecting to a master instance. 259 260 X11 and ssh-agent(1) forwarding is supported over these 261 multiplexed connections, however the display and agent forwarded 262 will be the one belonging to the master connection i.e. it is not 263 possible to forward multiple displays or agents. 264 265 Two additional options allow for opportunistic multiplexing: try 266 to use a master connection but fall back to creating a new one if 267 one does not already exist. These options are: M-bM-^@M-^\autoM-bM-^@M-^] and 268 M-bM-^@M-^\autoaskM-bM-^@M-^]. The latter requires confirmation like the M-bM-^@M-^\askM-bM-^@M-^] 269 option. 270 271 ControlPath 272 Specify the path to the control socket used for connection 273 sharing as described in the ControlMaster section above or the 274 string M-bM-^@M-^\noneM-bM-^@M-^] to disable connection sharing. In the path, M-bM-^@M-^X%LM-bM-^@M-^Y 275 will be substituted by the first component of the local host 276 name, M-bM-^@M-^X%lM-bM-^@M-^Y will be substituted by the local host name (including 277 any domain name), M-bM-^@M-^X%hM-bM-^@M-^Y will be substituted by the target host 278 name, M-bM-^@M-^X%nM-bM-^@M-^Y will be substituted by the original target host name 279 specified on the command line, M-bM-^@M-^X%pM-bM-^@M-^Y the destination port, M-bM-^@M-^X%rM-bM-^@M-^Y by 280 the remote login username, M-bM-^@M-^X%uM-bM-^@M-^Y by the username of the user 281 running ssh(1), and M-bM-^@M-^X%CM-bM-^@M-^Y by a hash of the concatenation: 282 %l%h%p%r. It is recommended that any ControlPath used for 283 opportunistic connection sharing include at least %h, %p, and %r 284 (or alternatively %C) and be placed in a directory that is not 285 writable by other users. This ensures that shared connections 286 are uniquely identified. 287 288 ControlPersist 289 When used in conjunction with ControlMaster, specifies that the 290 master connection should remain open in the background (waiting 291 for future client connections) after the initial client 292 connection has been closed. If set to M-bM-^@M-^\noM-bM-^@M-^], then the master 293 connection will not be placed into the background, and will close 294 as soon as the initial client connection is closed. If set to 295 M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\0M-bM-^@M-^], then the master connection will remain in the 296 background indefinitely (until killed or closed via a mechanism 297 such as the ssh(1) M-bM-^@M-^\-O exitM-bM-^@M-^] option). If set to a time in 298 seconds, or a time in any of the formats documented in 299 sshd_config(5), then the backgrounded master connection will 300 automatically terminate after it has remained idle (with no 301 client connections) for the specified time. 302 303 DynamicForward 304 Specifies that a TCP port on the local machine be forwarded over 305 the secure channel, and the application protocol is then used to 306 determine where to connect to from the remote machine. 307 308 The argument must be [bind_address:]port. IPv6 addresses can be 309 specified by enclosing addresses in square brackets. By default, 310 the local port is bound in accordance with the GatewayPorts 311 setting. However, an explicit bind_address may be used to bind 312 the connection to a specific address. The bind_address of 313 M-bM-^@M-^\localhostM-bM-^@M-^] indicates that the listening port be bound for local 314 use only, while an empty address or M-bM-^@M-^X*M-bM-^@M-^Y indicates that the port 315 should be available from all interfaces. 316 317 Currently the SOCKS4 and SOCKS5 protocols are supported, and 318 ssh(1) will act as a SOCKS server. Multiple forwardings may be 319 specified, and additional forwardings can be given on the command 320 line. Only the superuser can forward privileged ports. 321 322 EnableSSHKeysign 323 Setting this option to M-bM-^@M-^\yesM-bM-^@M-^] in the global client configuration 324 file /etc/ssh/ssh_config enables the use of the helper program 325 ssh-keysign(8) during HostbasedAuthentication. The argument must 326 be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is M-bM-^@M-^\noM-bM-^@M-^]. This option should be 327 placed in the non-hostspecific section. See ssh-keysign(8) for 328 more information. 329 330 EscapeChar 331 Sets the escape character (default: M-bM-^@M-^X~M-bM-^@M-^Y). The escape character 332 can also be set on the command line. The argument should be a 333 single character, M-bM-^@M-^X^M-bM-^@M-^Y followed by a letter, or M-bM-^@M-^\noneM-bM-^@M-^] to disable 334 the escape character entirely (making the connection transparent 335 for binary data). 336 337 ExitOnForwardFailure 338 Specifies whether ssh(1) should terminate the connection if it 339 cannot set up all requested dynamic, tunnel, local, and remote 340 port forwardings. The argument must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The 341 default is M-bM-^@M-^\noM-bM-^@M-^]. 342 343 FingerprintHash 344 Specifies the hash algorithm used when displaying key 345 fingerprints. Valid options are: M-bM-^@M-^\md5M-bM-^@M-^] and M-bM-^@M-^\sha256M-bM-^@M-^]. The 346 default is M-bM-^@M-^\sha256M-bM-^@M-^]. 347 348 ForwardAgent 349 Specifies whether the connection to the authentication agent (if 350 any) will be forwarded to the remote machine. The argument must 351 be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is M-bM-^@M-^\noM-bM-^@M-^]. 352 353 Agent forwarding should be enabled with caution. Users with the 354 ability to bypass file permissions on the remote host (for the 355 agent's Unix-domain socket) can access the local agent through 356 the forwarded connection. An attacker cannot obtain key material 357 from the agent, however they can perform operations on the keys 358 that enable them to authenticate using the identities loaded into 359 the agent. 360 361 ForwardX11 362 Specifies whether X11 connections will be automatically 363 redirected over the secure channel and DISPLAY set. The argument 364 must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is M-bM-^@M-^\noM-bM-^@M-^]. 365 366 X11 forwarding should be enabled with caution. Users with the 367 ability to bypass file permissions on the remote host (for the 368 user's X11 authorization database) can access the local X11 369 display through the forwarded connection. An attacker may then 370 be able to perform activities such as keystroke monitoring if the 371 ForwardX11Trusted option is also enabled. 372 373 ForwardX11Timeout 374 Specify a timeout for untrusted X11 forwarding using the format 375 described in the TIME FORMATS section of sshd_config(5). X11 376 connections received by ssh(1) after this time will be refused. 377 The default is to disable untrusted X11 forwarding after twenty 378 minutes has elapsed. 379 380 ForwardX11Trusted 381 If this option is set to M-bM-^@M-^\yesM-bM-^@M-^], remote X11 clients will have full 382 access to the original X11 display. 383 384 If this option is set to M-bM-^@M-^\noM-bM-^@M-^], remote X11 clients will be 385 considered untrusted and prevented from stealing or tampering 386 with data belonging to trusted X11 clients. Furthermore, the 387 xauth(1) token used for the session will be set to expire after 388 20 minutes. Remote clients will be refused access after this 389 time. 390 391 The default is M-bM-^@M-^\noM-bM-^@M-^]. 392 393 See the X11 SECURITY extension specification for full details on 394 the restrictions imposed on untrusted clients. 395 396 GatewayPorts 397 Specifies whether remote hosts are allowed to connect to local 398 forwarded ports. By default, ssh(1) binds local port forwardings 399 to the loopback address. This prevents other remote hosts from 400 connecting to forwarded ports. GatewayPorts can be used to 401 specify that ssh should bind local port forwardings to the 402 wildcard address, thus allowing remote hosts to connect to 403 forwarded ports. The argument must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The 404 default is M-bM-^@M-^\noM-bM-^@M-^]. 405 406 GlobalKnownHostsFile 407 Specifies one or more files to use for the global host key 408 database, separated by whitespace. The default is 409 /etc/ssh/ssh_known_hosts, /etc/ssh/ssh_known_hosts2. 410 411 GSSAPIAuthentication 412 Specifies whether user authentication based on GSSAPI is allowed. 413 The default is M-bM-^@M-^\noM-bM-^@M-^]. Note that this option applies to protocol 414 version 2 only. 415 416 GSSAPIDelegateCredentials 417 Forward (delegate) credentials to the server. The default is 418 M-bM-^@M-^\noM-bM-^@M-^]. Note that this option applies to protocol version 2 only. 419 420 HashKnownHosts 421 Indicates that ssh(1) should hash host names and addresses when 422 they are added to ~/.ssh/known_hosts. These hashed names may be 423 used normally by ssh(1) and sshd(8), but they do not reveal 424 identifying information should the file's contents be disclosed. 425 The default is M-bM-^@M-^\noM-bM-^@M-^]. Note that existing names and addresses in 426 known hosts files will not be converted automatically, but may be 427 manually hashed using ssh-keygen(1). 428 429 HostbasedAuthentication 430 Specifies whether to try rhosts based authentication with public 431 key authentication. The argument must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The 432 default is M-bM-^@M-^\noM-bM-^@M-^]. This option applies to protocol version 2 only 433 and is similar to RhostsRSAAuthentication. 434 435 HostbasedKeyTypes 436 Specifies the key types that will be used for hostbased 437 authentication as a comma-separated pattern list. The default 438 M-bM-^@M-^\*M-bM-^@M-^] will allow all key types. The -Q option of ssh(1) may be 439 used to list supported key types. 440 441 HostKeyAlgorithms 442 Specifies the protocol version 2 host key algorithms that the 443 client wants to use in order of preference. The default for this 444 option is: 445 446 ecdsa-sha2-nistp256-cert-v01 (a] openssh.com, 447 ecdsa-sha2-nistp384-cert-v01 (a] openssh.com, 448 ecdsa-sha2-nistp521-cert-v01 (a] openssh.com, 449 ssh-ed25519-cert-v01 (a] openssh.com, 450 ssh-rsa-cert-v01 (a] openssh.com,ssh-dss-cert-v01 (a] openssh.com, 451 ssh-rsa-cert-v00 (a] openssh.com,ssh-dss-cert-v00 (a] openssh.com, 452 ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521, 453 ssh-ed25519,ssh-rsa,ssh-dss 454 455 If hostkeys are known for the destination host then this default 456 is modified to prefer their algorithms. 457 458 The list of available key types may also be obtained using the -Q 459 option of ssh(1) with an argument of M-bM-^@M-^\keyM-bM-^@M-^]. 460 461 HostKeyAlias 462 Specifies an alias that should be used instead of the real host 463 name when looking up or saving the host key in the host key 464 database files. This option is useful for tunneling SSH 465 connections or for multiple servers running on a single host. 466 467 HostName 468 Specifies the real host name to log into. This can be used to 469 specify nicknames or abbreviations for hosts. If the hostname 470 contains the character sequence M-bM-^@M-^X%hM-bM-^@M-^Y, then this will be replaced 471 with the host name specified on the command line (this is useful 472 for manipulating unqualified names). The character sequence M-bM-^@M-^X%%M-bM-^@M-^Y 473 will be replaced by a single M-bM-^@M-^X%M-bM-^@M-^Y character, which may be used 474 when specifying IPv6 link-local addresses. 475 476 The default is the name given on the command line. Numeric IP 477 addresses are also permitted (both on the command line and in 478 HostName specifications). 479 480 IdentitiesOnly 481 Specifies that ssh(1) should only use the authentication identity 482 files configured in the ssh_config files, even if ssh-agent(1) or 483 a PKCS11Provider offers more identities. The argument to this 484 keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. This option is intended for 485 situations where ssh-agent offers many different identities. The 486 default is M-bM-^@M-^\noM-bM-^@M-^]. 487 488 IdentityFile 489 Specifies a file from which the user's DSA, ECDSA, Ed25519 or RSA 490 authentication identity is read. The default is ~/.ssh/identity 491 for protocol version 1, and ~/.ssh/id_dsa, ~/.ssh/id_ecdsa, 492 ~/.ssh/id_ed25519 and ~/.ssh/id_rsa for protocol version 2. 493 Additionally, any identities represented by the authentication 494 agent will be used for authentication unless IdentitiesOnly is 495 set. ssh(1) will try to load certificate information from the 496 filename obtained by appending -cert.pub to the path of a 497 specified IdentityFile. 498 499 The file name may use the tilde syntax to refer to a user's home 500 directory or one of the following escape characters: M-bM-^@M-^X%dM-bM-^@M-^Y (local 501 user's home directory), M-bM-^@M-^X%uM-bM-^@M-^Y (local user name), M-bM-^@M-^X%lM-bM-^@M-^Y (local host 502 name), M-bM-^@M-^X%hM-bM-^@M-^Y (remote host name) or M-bM-^@M-^X%rM-bM-^@M-^Y (remote user name). 503 504 It is possible to have multiple identity files specified in 505 configuration files; all these identities will be tried in 506 sequence. Multiple IdentityFile directives will add to the list 507 of identities tried (this behaviour differs from that of other 508 configuration directives). 509 510 IdentityFile may be used in conjunction with IdentitiesOnly to 511 select which identities in an agent are offered during 512 authentication. 513 514 IgnoreUnknown 515 Specifies a pattern-list of unknown options to be ignored if they 516 are encountered in configuration parsing. This may be used to 517 suppress errors if ssh_config contains options that are 518 unrecognised by ssh(1). It is recommended that IgnoreUnknown be 519 listed early in the configuration file as it will not be applied 520 to unknown options that appear before it. 521 522 IPQoS Specifies the IPv4 type-of-service or DSCP class for connections. 523 Accepted values are M-bM-^@M-^\af11M-bM-^@M-^], M-bM-^@M-^\af12M-bM-^@M-^], M-bM-^@M-^\af13M-bM-^@M-^], M-bM-^@M-^\af21M-bM-^@M-^], M-bM-^@M-^\af22M-bM-^@M-^], 524 M-bM-^@M-^\af23M-bM-^@M-^], M-bM-^@M-^\af31M-bM-^@M-^], M-bM-^@M-^\af32M-bM-^@M-^], M-bM-^@M-^\af33M-bM-^@M-^], M-bM-^@M-^\af41M-bM-^@M-^], M-bM-^@M-^\af42M-bM-^@M-^], M-bM-^@M-^\af43M-bM-^@M-^], M-bM-^@M-^\cs0M-bM-^@M-^], 525 M-bM-^@M-^\cs1M-bM-^@M-^], M-bM-^@M-^\cs2M-bM-^@M-^], M-bM-^@M-^\cs3M-bM-^@M-^], M-bM-^@M-^\cs4M-bM-^@M-^], M-bM-^@M-^\cs5M-bM-^@M-^], M-bM-^@M-^\cs6M-bM-^@M-^], M-bM-^@M-^\cs7M-bM-^@M-^], M-bM-^@M-^\efM-bM-^@M-^], 526 M-bM-^@M-^\lowdelayM-bM-^@M-^], M-bM-^@M-^\throughputM-bM-^@M-^], M-bM-^@M-^\reliabilityM-bM-^@M-^], or a numeric value. 527 This option may take one or two arguments, separated by 528 whitespace. If one argument is specified, it is used as the 529 packet class unconditionally. If two values are specified, the 530 first is automatically selected for interactive sessions and the 531 second for non-interactive sessions. The default is M-bM-^@M-^\lowdelayM-bM-^@M-^] 532 for interactive sessions and M-bM-^@M-^\throughputM-bM-^@M-^] for non-interactive 533 sessions. 534 535 KbdInteractiveAuthentication 536 Specifies whether to use keyboard-interactive authentication. 537 The argument to this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default 538 is M-bM-^@M-^\yesM-bM-^@M-^]. 539 540 KbdInteractiveDevices 541 Specifies the list of methods to use in keyboard-interactive 542 authentication. Multiple method names must be comma-separated. 543 The default is to use the server specified list. The methods 544 available vary depending on what the server supports. For an 545 OpenSSH server, it may be zero or more of: M-bM-^@M-^\bsdauthM-bM-^@M-^], M-bM-^@M-^\pamM-bM-^@M-^], and 546 M-bM-^@M-^\skeyM-bM-^@M-^]. 547 548 KexAlgorithms 549 Specifies the available KEX (Key Exchange) algorithms. Multiple 550 algorithms must be comma-separated. The default is: 551 552 curve25519-sha256 (a] libssh.org, 553 ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521, 554 diffie-hellman-group-exchange-sha256, 555 diffie-hellman-group14-sha1, 556 diffie-hellman-group-exchange-sha1, 557 diffie-hellman-group1-sha1 558 559 The list of available key exchange algorithms may also be 560 obtained using the -Q option of ssh(1) with an argument of M-bM-^@M-^\kexM-bM-^@M-^]. 561 562 LocalCommand 563 Specifies a command to execute on the local machine after 564 successfully connecting to the server. The command string 565 extends to the end of the line, and is executed with the user's 566 shell. The following escape character substitutions will be 567 performed: M-bM-^@M-^X%dM-bM-^@M-^Y (local user's home directory), M-bM-^@M-^X%hM-bM-^@M-^Y (remote host 568 name), M-bM-^@M-^X%lM-bM-^@M-^Y (local host name), M-bM-^@M-^X%nM-bM-^@M-^Y (host name as provided on the 569 command line), M-bM-^@M-^X%pM-bM-^@M-^Y (remote port), M-bM-^@M-^X%rM-bM-^@M-^Y (remote user name) or 570 M-bM-^@M-^X%uM-bM-^@M-^Y (local user name) or M-bM-^@M-^X%CM-bM-^@M-^Y by a hash of the concatenation: 571 %l%h%p%r. 572 573 The command is run synchronously and does not have access to the 574 session of the ssh(1) that spawned it. It should not be used for 575 interactive commands. 576 577 This directive is ignored unless PermitLocalCommand has been 578 enabled. 579 580 LocalForward 581 Specifies that a TCP port on the local machine be forwarded over 582 the secure channel to the specified host and port from the remote 583 machine. The first argument must be [bind_address:]port and the 584 second argument must be host:hostport. IPv6 addresses can be 585 specified by enclosing addresses in square brackets. Multiple 586 forwardings may be specified, and additional forwardings can be 587 given on the command line. Only the superuser can forward 588 privileged ports. By default, the local port is bound in 589 accordance with the GatewayPorts setting. However, an explicit 590 bind_address may be used to bind the connection to a specific 591 address. The bind_address of M-bM-^@M-^\localhostM-bM-^@M-^] indicates that the 592 listening port be bound for local use only, while an empty 593 address or M-bM-^@M-^X*M-bM-^@M-^Y indicates that the port should be available from 594 all interfaces. 595 596 LogLevel 597 Gives the verbosity level that is used when logging messages from 598 ssh(1). The possible values are: QUIET, FATAL, ERROR, INFO, 599 VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO. 600 DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify 601 higher levels of verbose output. 602 603 MACs Specifies the MAC (message authentication code) algorithms in 604 order of preference. The MAC algorithm is used in protocol 605 version 2 for data integrity protection. Multiple algorithms 606 must be comma-separated. The algorithms that contain M-bM-^@M-^\-etmM-bM-^@M-^] 607 calculate the MAC after encryption (encrypt-then-mac). These are 608 considered safer and their use recommended. The default is: 609 610 umac-64-etm (a] openssh.com,umac-128-etm (a] openssh.com, 611 hmac-sha2-256-etm (a] openssh.com,hmac-sha2-512-etm (a] openssh.com, 612 umac-64 (a] openssh.com,umac-128 (a] openssh.com, 613 hmac-sha2-256,hmac-sha2-512, 614 hmac-md5-etm (a] openssh.com,hmac-sha1-etm (a] openssh.com, 615 hmac-ripemd160-etm (a] openssh.com, 616 hmac-sha1-96-etm (a] openssh.com,hmac-md5-96-etm (a] openssh.com, 617 hmac-md5,hmac-sha1,hmac-ripemd160, 618 hmac-sha1-96,hmac-md5-96 619 620 The list of available MAC algorithms may also be obtained using 621 the -Q option of ssh(1) with an argument of M-bM-^@M-^\macM-bM-^@M-^]. 622 623 NoHostAuthenticationForLocalhost 624 This option can be used if the home directory is shared across 625 machines. In this case localhost will refer to a different 626 machine on each of the machines and the user will get many 627 warnings about changed host keys. However, this option disables 628 host authentication for localhost. The argument to this keyword 629 must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is to check the host key for 630 localhost. 631 632 NumberOfPasswordPrompts 633 Specifies the number of password prompts before giving up. The 634 argument to this keyword must be an integer. The default is 3. 635 636 PasswordAuthentication 637 Specifies whether to use password authentication. The argument 638 to this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is M-bM-^@M-^\yesM-bM-^@M-^]. 639 640 PermitLocalCommand 641 Allow local command execution via the LocalCommand option or 642 using the !command escape sequence in ssh(1). The argument must 643 be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is M-bM-^@M-^\noM-bM-^@M-^]. 644 645 PKCS11Provider 646 Specifies which PKCS#11 provider to use. The argument to this 647 keyword is the PKCS#11 shared library ssh(1) should use to 648 communicate with a PKCS#11 token providing the user's private RSA 649 key. 650 651 Port Specifies the port number to connect on the remote host. The 652 default is 22. 653 654 PreferredAuthentications 655 Specifies the order in which the client should try protocol 2 656 authentication methods. This allows a client to prefer one 657 method (e.g. keyboard-interactive) over another method (e.g. 658 password). The default is: 659 660 gssapi-with-mic,hostbased,publickey, 661 keyboard-interactive,password 662 663 Protocol 664 Specifies the protocol versions ssh(1) should support in order of 665 preference. The possible values are M-bM-^@M-^X1M-bM-^@M-^Y and M-bM-^@M-^X2M-bM-^@M-^Y. Multiple 666 versions must be comma-separated. When this option is set to 667 M-bM-^@M-^\2,1M-bM-^@M-^] ssh will try version 2 and fall back to version 1 if 668 version 2 is not available. The default is M-bM-^@M-^X2M-bM-^@M-^Y. 669 670 ProxyCommand 671 Specifies the command to use to connect to the server. The 672 command string extends to the end of the line, and is executed 673 using the user's shell M-bM-^@M-^XexecM-bM-^@M-^Y directive to avoid a lingering 674 shell process. 675 676 In the command string, any occurrence of M-bM-^@M-^X%hM-bM-^@M-^Y will be substituted 677 by the host name to connect, M-bM-^@M-^X%pM-bM-^@M-^Y by the port, and M-bM-^@M-^X%rM-bM-^@M-^Y by the 678 remote user name. The command can be basically anything, and 679 should read from its standard input and write to its standard 680 output. It should eventually connect an sshd(8) server running 681 on some machine, or execute sshd -i somewhere. Host key 682 management will be done using the HostName of the host being 683 connected (defaulting to the name typed by the user). Setting 684 the command to M-bM-^@M-^\noneM-bM-^@M-^] disables this option entirely. Note that 685 CheckHostIP is not available for connects with a proxy command. 686 687 This directive is useful in conjunction with nc(1) and its proxy 688 support. For example, the following directive would connect via 689 an HTTP proxy at 192.0.2.0: 690 691 ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p 692 693 ProxyUseFdpass 694 Specifies that ProxyCommand will pass a connected file descriptor 695 back to ssh(1) instead of continuing to execute and pass data. 696 The default is M-bM-^@M-^\noM-bM-^@M-^]. 697 698 PubkeyAuthentication 699 Specifies whether to try public key authentication. The argument 700 to this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is M-bM-^@M-^\yesM-bM-^@M-^]. 701 This option applies to protocol version 2 only. 702 703 RekeyLimit 704 Specifies the maximum amount of data that may be transmitted 705 before the session key is renegotiated, optionally followed a 706 maximum amount of time that may pass before the session key is 707 renegotiated. The first argument is specified in bytes and may 708 have a suffix of M-bM-^@M-^XKM-bM-^@M-^Y, M-bM-^@M-^XMM-bM-^@M-^Y, or M-bM-^@M-^XGM-bM-^@M-^Y to indicate Kilobytes, 709 Megabytes, or Gigabytes, respectively. The default is between 710 M-bM-^@M-^X1GM-bM-^@M-^Y and M-bM-^@M-^X4GM-bM-^@M-^Y, depending on the cipher. The optional second 711 value is specified in seconds and may use any of the units 712 documented in the TIME FORMATS section of sshd_config(5). The 713 default value for RekeyLimit is M-bM-^@M-^\default noneM-bM-^@M-^], which means that 714 rekeying is performed after the cipher's default amount of data 715 has been sent or received and no time based rekeying is done. 716 This option applies to protocol version 2 only. 717 718 RemoteForward 719 Specifies that a TCP port on the remote machine be forwarded over 720 the secure channel to the specified host and port from the local 721 machine. The first argument must be [bind_address:]port and the 722 second argument must be host:hostport. IPv6 addresses can be 723 specified by enclosing addresses in square brackets. Multiple 724 forwardings may be specified, and additional forwardings can be 725 given on the command line. Privileged ports can be forwarded 726 only when logging in as root on the remote machine. 727 728 If the port argument is M-bM-^@M-^X0M-bM-^@M-^Y, the listen port will be dynamically 729 allocated on the server and reported to the client at run time. 730 731 If the bind_address is not specified, the default is to only bind 732 to loopback addresses. If the bind_address is M-bM-^@M-^X*M-bM-^@M-^Y or an empty 733 string, then the forwarding is requested to listen on all 734 interfaces. Specifying a remote bind_address will only succeed 735 if the server's GatewayPorts option is enabled (see 736 sshd_config(5)). 737 738 RequestTTY 739 Specifies whether to request a pseudo-tty for the session. The 740 argument may be one of: M-bM-^@M-^\noM-bM-^@M-^] (never request a TTY), M-bM-^@M-^\yesM-bM-^@M-^] (always 741 request a TTY when standard input is a TTY), M-bM-^@M-^\forceM-bM-^@M-^] (always 742 request a TTY) or M-bM-^@M-^\autoM-bM-^@M-^] (request a TTY when opening a login 743 session). This option mirrors the -t and -T flags for ssh(1). 744 745 RevokedHostKeys 746 Specifies revoked host public keys. Keys listed in this file 747 will be refused for host authentication. Note that if this file 748 does not exist or is not readable, then host authentication will 749 be refused for all hosts. Keys may be specified as a text file, 750 listing one public key per line, or as an OpenSSH Key Revocation 751 List (KRL) as generated by ssh-keygen(1). For more information 752 on KRLs, see the KEY REVOCATION LISTS section in ssh-keygen(1). 753 754 RhostsRSAAuthentication 755 Specifies whether to try rhosts based authentication with RSA 756 host authentication. The argument must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The 757 default is M-bM-^@M-^\noM-bM-^@M-^]. This option applies to protocol version 1 only 758 and requires ssh(1) to be setuid root. 759 760 RSAAuthentication 761 Specifies whether to try RSA authentication. The argument to 762 this keyword must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. RSA authentication will only 763 be attempted if the identity file exists, or an authentication 764 agent is running. The default is M-bM-^@M-^\yesM-bM-^@M-^]. Note that this option 765 applies to protocol version 1 only. 766 767 SendEnv 768 Specifies what variables from the local environ(7) should be sent 769 to the server. Note that environment passing is only supported 770 for protocol 2. The server must also support it, and the server 771 must be configured to accept these environment variables. Refer 772 to AcceptEnv in sshd_config(5) for how to configure the server. 773 Variables are specified by name, which may contain wildcard 774 characters. Multiple environment variables may be separated by 775 whitespace or spread across multiple SendEnv directives. The 776 default is not to send any environment variables. 777 778 See PATTERNS for more information on patterns. 779 780 ServerAliveCountMax 781 Sets the number of server alive messages (see below) which may be 782 sent without ssh(1) receiving any messages back from the server. 783 If this threshold is reached while server alive messages are 784 being sent, ssh will disconnect from the server, terminating the 785 session. It is important to note that the use of server alive 786 messages is very different from TCPKeepAlive (below). The server 787 alive messages are sent through the encrypted channel and 788 therefore will not be spoofable. The TCP keepalive option 789 enabled by TCPKeepAlive is spoofable. The server alive mechanism 790 is valuable when the client or server depend on knowing when a 791 connection has become inactive. 792 793 The default value is 3. If, for example, ServerAliveInterval 794 (see below) is set to 15 and ServerAliveCountMax is left at the 795 default, if the server becomes unresponsive, ssh will disconnect 796 after approximately 45 seconds. This option applies to protocol 797 version 2 only. 798 799 ServerAliveInterval 800 Sets a timeout interval in seconds after which if no data has 801 been received from the server, ssh(1) will send a message through 802 the encrypted channel to request a response from the server. The 803 default is 0, indicating that these messages will not be sent to 804 the server. This option applies to protocol version 2 only. 805 806 StreamLocalBindMask 807 Sets the octal file creation mode mask (umask) used when creating 808 a Unix-domain socket file for local or remote port forwarding. 809 This option is only used for port forwarding to a Unix-domain 810 socket file. 811 812 The default value is 0177, which creates a Unix-domain socket 813 file that is readable and writable only by the owner. Note that 814 not all operating systems honor the file mode on Unix-domain 815 socket files. 816 817 StreamLocalBindUnlink 818 Specifies whether to remove an existing Unix-domain socket file 819 for local or remote port forwarding before creating a new one. 820 If the socket file already exists and StreamLocalBindUnlink is 821 not enabled, ssh will be unable to forward the port to the Unix- 822 domain socket file. This option is only used for port forwarding 823 to a Unix-domain socket file. 824 825 The argument must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is M-bM-^@M-^\noM-bM-^@M-^]. 826 827 StrictHostKeyChecking 828 If this flag is set to M-bM-^@M-^\yesM-bM-^@M-^], ssh(1) will never automatically add 829 host keys to the ~/.ssh/known_hosts file, and refuses to connect 830 to hosts whose host key has changed. This provides maximum 831 protection against trojan horse attacks, though it can be 832 annoying when the /etc/ssh/ssh_known_hosts file is poorly 833 maintained or when connections to new hosts are frequently made. 834 This option forces the user to manually add all new hosts. If 835 this flag is set to M-bM-^@M-^\noM-bM-^@M-^], ssh will automatically add new host 836 keys to the user known hosts files. If this flag is set to 837 M-bM-^@M-^\askM-bM-^@M-^], new host keys will be added to the user known host files 838 only after the user has confirmed that is what they really want 839 to do, and ssh will refuse to connect to hosts whose host key has 840 changed. The host keys of known hosts will be verified 841 automatically in all cases. The argument must be M-bM-^@M-^\yesM-bM-^@M-^], M-bM-^@M-^\noM-bM-^@M-^], or 842 M-bM-^@M-^\askM-bM-^@M-^]. The default is M-bM-^@M-^\askM-bM-^@M-^]. 843 844 TCPKeepAlive 845 Specifies whether the system should send TCP keepalive messages 846 to the other side. If they are sent, death of the connection or 847 crash of one of the machines will be properly noticed. However, 848 this means that connections will die if the route is down 849 temporarily, and some people find it annoying. 850 851 The default is M-bM-^@M-^\yesM-bM-^@M-^] (to send TCP keepalive messages), and the 852 client will notice if the network goes down or the remote host 853 dies. This is important in scripts, and many users want it too. 854 855 To disable TCP keepalive messages, the value should be set to 856 M-bM-^@M-^\noM-bM-^@M-^]. 857 858 Tunnel Request tun(4) device forwarding between the client and the 859 server. The argument must be M-bM-^@M-^\yesM-bM-^@M-^], M-bM-^@M-^\point-to-pointM-bM-^@M-^] (layer 3), 860 M-bM-^@M-^\ethernetM-bM-^@M-^] (layer 2), or M-bM-^@M-^\noM-bM-^@M-^]. Specifying M-bM-^@M-^\yesM-bM-^@M-^] requests the 861 default tunnel mode, which is M-bM-^@M-^\point-to-pointM-bM-^@M-^]. The default is 862 M-bM-^@M-^\noM-bM-^@M-^]. 863 864 TunnelDevice 865 Specifies the tun(4) devices to open on the client (local_tun) 866 and the server (remote_tun). 867 868 The argument must be local_tun[:remote_tun]. The devices may be 869 specified by numerical ID or the keyword M-bM-^@M-^\anyM-bM-^@M-^], which uses the 870 next available tunnel device. If remote_tun is not specified, it 871 defaults to M-bM-^@M-^\anyM-bM-^@M-^]. The default is M-bM-^@M-^\any:anyM-bM-^@M-^]. 872 873 UpdateHostKeys 874 Specifies whether ssh(1) should accept notifications of 875 additional hostkeys from the server sent after authentication has 876 completed and add them to UserKnownHostsFile. The argument must 877 be M-bM-^@M-^\yesM-bM-^@M-^], M-bM-^@M-^\noM-bM-^@M-^] (the default) or M-bM-^@M-^\askM-bM-^@M-^]. Enabling this option 878 allows learning alternate hostkeys for a server and supports 879 graceful key rotation by allowing a server to send replacement 880 public keys before old ones are removed. Additional hostkeys are 881 only accepted if the key used to authenticate the host was 882 already trusted or explicity accepted by the user. If 883 UpdateHostKeys is set to M-bM-^@M-^\askM-bM-^@M-^], then the user is asked to confirm 884 the modifications to the known_hosts file. Confirmation is 885 currently incompatible with ControlPersist, and will be disabled 886 if it is enabled. 887 888 Presently, only sshd(8) from OpenSSH 6.8 and greater support the 889 M-bM-^@M-^\hostkeys (a] openssh.comM-bM-^@M-^] protocol extension used to inform the 890 client of all the server's hostkeys. 891 892 UsePrivilegedPort 893 Specifies whether to use a privileged port for outgoing 894 connections. The argument must be M-bM-^@M-^\yesM-bM-^@M-^] or M-bM-^@M-^\noM-bM-^@M-^]. The default is 895 M-bM-^@M-^\noM-bM-^@M-^]. If set to M-bM-^@M-^\yesM-bM-^@M-^], ssh(1) must be setuid root. Note that 896 this option must be set to M-bM-^@M-^\yesM-bM-^@M-^] for RhostsRSAAuthentication with 897 older servers. 898 899 User Specifies the user to log in as. This can be useful when a 900 different user name is used on different machines. This saves 901 the trouble of having to remember to give the user name on the 902 command line. 903 904 UserKnownHostsFile 905 Specifies one or more files to use for the user host key 906 database, separated by whitespace. The default is 907 ~/.ssh/known_hosts, ~/.ssh/known_hosts2. 908 909 VerifyHostKeyDNS 910 Specifies whether to verify the remote key using DNS and SSHFP 911 resource records. If this option is set to M-bM-^@M-^\yesM-bM-^@M-^], the client 912 will implicitly trust keys that match a secure fingerprint from 913 DNS. Insecure fingerprints will be handled as if this option was 914 set to M-bM-^@M-^\askM-bM-^@M-^]. If this option is set to M-bM-^@M-^\askM-bM-^@M-^], information on 915 fingerprint match will be displayed, but the user will still need 916 to confirm new host keys according to the StrictHostKeyChecking 917 option. The argument must be M-bM-^@M-^\yesM-bM-^@M-^], M-bM-^@M-^\noM-bM-^@M-^], or M-bM-^@M-^\askM-bM-^@M-^]. The default 918 is M-bM-^@M-^\noM-bM-^@M-^]. Note that this option applies to protocol version 2 919 only. 920 921 See also VERIFYING HOST KEYS in ssh(1). 922 923 VisualHostKey 924 If this flag is set to M-bM-^@M-^\yesM-bM-^@M-^], an ASCII art representation of the 925 remote host key fingerprint is printed in addition to the 926 fingerprint string at login and for unknown host keys. If this 927 flag is set to M-bM-^@M-^\noM-bM-^@M-^], no fingerprint strings are printed at login 928 and only the fingerprint string will be printed for unknown host 929 keys. The default is M-bM-^@M-^\noM-bM-^@M-^]. 930 931 XAuthLocation 932 Specifies the full pathname of the xauth(1) program. The default 933 is /usr/X11R6/bin/xauth. 934 935 PATTERNS 936 A pattern consists of zero or more non-whitespace characters, M-bM-^@M-^X*M-bM-^@M-^Y (a 937 wildcard that matches zero or more characters), or M-bM-^@M-^X?M-bM-^@M-^Y (a wildcard that 938 matches exactly one character). For example, to specify a set of 939 declarations for any host in the M-bM-^@M-^\.co.ukM-bM-^@M-^] set of domains, the following 940 pattern could be used: 941 942 Host *.co.uk 943 944 The following pattern would match any host in the 192.168.0.[0-9] network 945 range: 946 947 Host 192.168.0.? 948 949 A pattern-list is a comma-separated list of patterns. Patterns within 950 pattern-lists may be negated by preceding them with an exclamation mark 951 (M-bM-^@M-^X!M-bM-^@M-^Y). For example, to allow a key to be used from anywhere within an 952 organization except from the M-bM-^@M-^\dialupM-bM-^@M-^] pool, the following entry (in 953 authorized_keys) could be used: 954 955 from="!*.dialup.example.com,*.example.com" 956 957 FILES 958 ~/.ssh/config 959 This is the per-user configuration file. The format of this file 960 is described above. This file is used by the SSH client. 961 Because of the potential for abuse, this file must have strict 962 permissions: read/write for the user, and not accessible by 963 others. 964 965 /etc/ssh/ssh_config 966 Systemwide configuration file. This file provides defaults for 967 those values that are not specified in the user's configuration 968 file, and for those users who do not have a configuration file. 969 This file must be world-readable. 970 971 SEE ALSO 972 ssh(1) 973 974 AUTHORS 975 OpenSSH is a derivative of the original and free ssh 1.2.12 release by 976 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo 977 de Raadt and Dug Song removed many bugs, re-added newer features and 978 created OpenSSH. Markus Friedl contributed the support for SSH protocol 979 versions 1.5 and 2.0. 980 981 OpenBSD 5.7 February 20, 2015 OpenBSD 5.7 982
