Manual Pages for UNIX Darwin command on man ssh

Manual Pages for UNIX Darwin command on man ssh_config

SSHCONFIG(5) BSD File Formats Manual SSHCONFIG(5)

NAME

sssshhccoonnffiigg - OpenSSH SSH client configuration files

SYNOPSIS

~~//..sssshh//ccoonnffiigg //eettcc//sssshhccoonnffiigg

DESCRIPTION

ssh(1) obtains configuration data from the following sources in the fol-

lowing order:

1. command-line options

2. user's configuration file (~/.ssh/config)

3. system-wide configuration file (/etc/sshconfig)

For each parameter, the first obtained value will be used. The configu-

ration files contain sections separated by ``Host'' specifications, and that section is only applied for hosts that match one of the patterns given in the specification. The matched host name is the one given on the command line.

Since the first obtained value for each parameter is used, more host-spe-

cific declarations should be given near the beginning of the file, and general defaults at the end. The configuration file has the following format:

Empty lines and lines starting with `#' are comments. Otherwise a line

is of the format ``keyword arguments''. Configuration options may be separated by whitespace or optional whitespace and exactly one `='; the

latter format is useful to avoid the need to quote whitespace when speci-

fying configuration options using the sssshh, ssccpp, and ssffttpp -oo option.

Arguments may optionally be enclosed in double quotes (") in order to represent arguments containing spaces.

The possible keywords and their meanings are as follows (note that key-

words are case-insensitive and arguments are case-sensitive):

HHoosstt Restricts the following declarations (up to the next HHoosstt key-

word) to be only for those hosts that match one of the patterns given after the keyword. If more than one pattern is provided,

they should be separated by whitepsace. A single `*' as a pat-

tern can be used to provide global defaults for all hosts. The host is the hostname argument given on the command line (i.e. the

name is not converted to a canonicalized host name before match-

ing). See PATTERNS for more information on patterns. AAddddrreessssFFaammiillyy Specifies which address family to use when connecting. Valid arguments are ``any'', ``inet'' (use IPv4 only), or ``inet6'' (use IPv6 only). BBaattcchhMMooddee If set to ``yes'', passphrase/password querying will be disabled. This option is useful in scripts and other batch jobs where no user is present to supply the password. The argument must be ``yes'' or ``no''. The default is ``no''. BBiinnddAAddddrreessss Use the specified address on the local machine as the source address of the connection. Only useful on systems with more than one address. Note that this option does not work if UUsseePPrriivviilleeggeeddPPoorrtt is set to ``yes''. CChhaalllleennggeeRReessppoonnsseeAAuutthheennttiiccaattiioonn

Specifies whether to use challenge-response authentication. The

argument to this keyword must be ``yes'' or ``no''. The default is ``yes''. CChheecckkHHoossttIIPP If this flag is set to ``yes'', ssh(1) will additionally check the host IP address in the knownhosts file. This allows ssh to detect if a host key changed due to DNS spoofing. If the option is set to ``no'', the check will not be executed. The default is ``yes''.

CCiipphheerr Specifies the cipher to use for encrypting the session in proto-

col version 1. Currently, ``blowfish'', ``3des'', and ``des'' are supported. des is only supported in the ssh(1) client for interoperability with legacy protocol 1 implementations that do not support the 3des cipher. Its use is strongly discouraged due to cryptographic weaknesses. The default is ``3des''. CCiipphheerrss Specifies the ciphers allowed for protocol version 2 in order of

preference. Multiple ciphers must be comma-separated. The sup-

ported ciphers are ``3des-cbc'', ``aes128-cbc'', ``aes192-cbc'',

``aes256-cbc'', ``aes128-ctr'', ``aes192-ctr'', ``aes256-ctr'',

``arcfour128'', ``arcfour256'', ``arcfour'', ``blowfish-cbc'',

and ``cast128-cbc''. The default is:

aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,

arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,

aes192-ctr,aes256-ctr

CClleeaarrAAllllFFoorrwwaarrddiinnggss Specifies that all local, remote, and dynamic port forwardings specified in the configuration files or on the command line be cleared. This option is primarily useful when used from the

ssh(1) command line to clear port forwardings set in configura-

tion files, and is automatically set by scp(1) and sftp(1). The argument must be ``yes'' or ``no''. The default is ``no''. CCoommpprreessssiioonn Specifies whether to use compression. The argument must be ``yes'' or ``no''. The default is ``no''. CCoommpprreessssiioonnLLeevveell Specifies the compression level to use if compression is enabled. The argument must be an integer from 1 (fast) to 9 (slow, best). The default level is 6, which is good for most applications. The meaning of the values is the same as in gzip(1). Note that this option applies to protocol version 1 only. CCoonnnneeccttiioonnAAtttteemmppttss Specifies the number of tries (one per second) to make before exiting. The argument must be an integer. This may be useful in scripts if the connection sometimes fails. The default is 1. CCoonnnneeccttTTiimmeeoouutt Specifies the timeout (in seconds) used when connecting to the SSH server, instead of using the default system TCP timeout. This value is used only when the target is down or really unreachable, not when it refuses the connection. CCoonnttrroollMMaasstteerr Enables the sharing of multiple sessions over a single network

connection. When set to ``yes'', ssh(1) will listen for connec-

tions on a control socket specified using the CCoonnttrroollPPaatthh argu-

ment. Additional sessions can connect to this socket using the same CCoonnttrroollPPaatthh with CCoonnttrroollMMaasstteerr set to ``no'' (the default). These sessions will try to reuse the master instance's network connection rather than initiating new ones, but will fall back to connecting normally if the control socket does not exist, or is not listening.

Setting this to ``ask'' will cause ssh to listen for control con-

nections, but require confirmation using the SSHASKPASS program

before they are accepted (see ssh-add(1) for details). If the

CCoonnttrroollPPaatthh cannot be opened, ssh will continue without connect-

ing to a master instance.

X11 and ssh-agent(1) forwarding is supported over these multi-

plexed connections, however the display and agent forwarded will

be the one belonging to the master connection i.e. it is not pos-

sible to forward multiple displays or agents. Two additional options allow for opportunistic multiplexing: try to use a master connection but fall back to creating a new one if one does not already exist. These options are: ``auto'' and ``autoask''. The latter requires confirmation like the ``ask'' option. CCoonnttrroollPPaatthh

Specify the path to the control socket used for connection shar-

ing as described in the CCoonnttrroollMMaasstteerr section above or the string

``none'' to disable connection sharing. In the path, `%l' will

be substituted by the local host name, `%h' will be substituted

by the target host name, `%p' the port, and `%r' by the remote

opportunistic connection sharing include at least %h, %p, and %r.

This ensures that shared connections are uniquely identified. DDyynnaammiiccFFoorrwwaarrdd Specifies that a TCP port on the local machine be forwarded over the secure channel, and the application protocol is then used to determine where to connect to from the remote machine. The argument must be [bindaddress:]port. IPv6 addresses can be specified by enclosing addresses in square brackets or by using an alternative syntax: [bindaddress/]port. By default, the local port is bound in accordance with the GGaatteewwaayyPPoorrttss setting.

However, an explicit bindaddress may be used to bind the connec-

tion to a specific address. The bindaddress of ``localhost'' indicates that the listening port be bound for local use only, while an empty address or `*' indicates that the port should be available from all interfaces. Currently the SOCKS4 and SOCKS5 protocols are supported, and ssh(1) will act as a SOCKS server. Multiple forwardings may be specified, and additional forwardings can be given on the command line. Only the superuser can forward privileged ports. EEnnaabblleeSSSSHHKKeeyyssiiggnn Setting this option to ``yes'' in the global client configuration file /etc/sshconfig enables the use of the helper program

ssh-keysign(8) during HHoossttbbaasseeddAAuutthheennttiiccaattiioonn. The argument must

be ``yes'' or ``no''. The default is ``no''. This option should

be placed in the non-hostspecific section. See ssh-keysign(8)

for more information. EEssccaappeeCChhaarr Sets the escape character (default: `~'). The escape character can also be set on the command line. The argument should be a

single character, `^' followed by a letter, or ``none'' to dis-

able the escape character entirely (making the connection trans-

parent for binary data). EExxiittOOnnFFoorrwwaarrddFFaaiilluurree Specifies whether ssh(1) should terminate the connection if it cannot set up all requested dynamic, tunnel, local, and remote port forwardings. The argument must be ``yes'' or ``no''. The default is ``no''. FFoorrwwaarrddAAggeenntt Specifies whether the connection to the authentication agent (if any) will be forwarded to the remote machine. The argument must be ``yes'' or ``no''. The default is ``no''. Agent forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the

agent's Unix-domain socket) can access the local agent through

the forwarded connection. An attacker cannot obtain key material from the agent, however they can perform operations on the keys that enable them to authenticate using the identities loaded into the agent. FFoorrwwaarrddXX1111

Specifies whether X11 connections will be automatically redi-

rected over the secure channel and DISPLAY set. The argument must be ``yes'' or ``no''. The default is ``no''. X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the

user's X11 authorization database) can access the local X11 dis-

play through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring if the FFoorrwwaarrddXX1111TTrruusstteedd option is also enabled. FFoorrwwaarrddXX1111TTrruusstteedd If this option is set to ``yes'', remote X11 clients will have full access to the original X11 display.

If this option is set to ``no'', remote X11 clients will be con-

sidered untrusted and prevented from stealing or tampering with data belonging to trusted X11 clients. Furthermore, the xauth(1)

token used for the session will be set to expire after 20 min-

utes. Remote clients will be refused access after this time. The default is ``no''. See the X11 SECURITY extension specification for full details on the restrictions imposed on untrusted clients. GGaatteewwaayyPPoorrttss Specifies whether remote hosts are allowed to connect to local forwarded ports. By default, ssh(1) binds local port forwardings to the loopback address. This prevents other remote hosts from

connecting to forwarded ports. GGaatteewwaayyPPoorrttss can be used to spec-

ify that ssh should bind local port forwardings to the wildcard address, thus allowing remote hosts to connect to forwarded ports. The argument must be ``yes'' or ``no''. The default is ``no''. GGlloobbaallKKnnoowwnnHHoossttssFFiillee Specifies a file to use for the global host key database instead of /etc/sshknownhosts. GGSSSSAAPPIIAAuutthheennttiiccaattiioonn Specifies whether user authentication based on GSSAPI is allowed.

The default is ``yes''. Note that this option applies to proto-

col version 2 only. GGSSSSAAPPIIKKeeyyEExxcchhaannggee Specifies whether key exchange based on GSSAPI may be used. When using GSSAPI key exchange the server need not have a host key.

The default is ``yes''. Note that this option applies to proto-

col version 2 only. GGSSSSAAPPIIDDeelleeggaatteeCCrreeddeennttiiaallss Forward (delegate) credentials to the server. The default is ``no''. Note that this option applies to protocol version 2 only. GGSSSSAAPPIITTrruussttDDnnss Set to ``yes'' to indicate that the DNS is trusted to securely canonicalize the name of the host being connected to. If ``no'', the hostname entered on the command line will be passed untouched to the GSSAPI library. The default is ``no''. This option only applies to protocol version 2 connections using GSSAPI. HHaasshhKKnnoowwnnHHoossttss Indicates that ssh(1) should hash host names and addresses when they are added to ~/.ssh/knownhosts. These hashed names may be

used normally by ssh(1) and sshd(8), but they do not reveal iden-

tifying information should the file's contents be disclosed. The default is ``no''. Note that existing names and addresses in known hosts files will not be converted automatically, but may be

manually hashed using ssh-keygen(1).

HHoossttbbaasseeddAAuutthheennttiiccaattiioonn Specifies whether to try rhosts based authentication with public key authentication. The argument must be ``yes'' or ``no''. The default is ``no''. This option applies to protocol version 2 only and is similar to RRhhoossttssRRSSAAAAuutthheennttiiccaattiioonn. HHoossttKKeeyyAAllggoorriitthhmmss Specifies the protocol version 2 host key algorithms that the client wants to use in order of preference. The default for this

option is: ``ssh-rsa,ssh-dss''.

HHoossttKKeeyyAAlliiaass Specifies an alias that should be used instead of the real host

name when looking up or saving the host key in the host key data-

base files. This option is useful for tunneling SSH connections or for multiple servers running on a single host. HHoossttNNaammee Specifies the real host name to log into. This can be used to specify nicknames or abbreviations for hosts. The default is the name given on the command line. Numeric IP addresses are also

permitted (both on the command line and in HHoossttNNaammee specifica-

tions). IIddeennttiittiieessOOnnllyy Specifies that ssh(1) should only use the authentication identity

files configured in the sssshhccoonnffiigg files, even if ssh-agent(1)

offers more identities. The argument to this keyword must be ``yes'' or ``no''. This option is intended for situations where

ssh-agent offers many different identities. The default is

``no''. IIddeennttiittyyFFiillee Specifies a file from which the user's RSA or DSA authentication identity is read. The default is ~/.ssh/identity for protocol

version 1, and ~/.ssh/idrsa and ~/.ssh/iddsa for protocol ver-

sion 2. Additionally, any identities represented by the authen-

tication agent will be used for authentication. The file name may use the tilde syntax to refer to a user's home

directory or one of the following escape characters: `%d' (local

user's home directory), `%u' (local user name), `%l' (local host

name), `%h' (remote host name) or `%r' (remote user name).

It is possible to have multiple identity files specified in con-

figuration files; all these identities will be tried in sequence. KKbbddIInntteerraaccttiivveeAAuutthheennttiiccaattiioonn

Specifies whether to use keyboard-interactive authentication.

The argument to this keyword must be ``yes'' or ``no''. The default is ``yes''. KKbbddIInntteerraaccttiivveeDDeevviicceess

Specifies the list of methods to use in keyboard-interactive

authentication. Multiple method names must be comma-separated.

The default is to use the server specified list. The methods available vary depending on what the server supports. For an OpenSSH server, it may be zero or more of: ``bsdauth'', ``pam'', and ``skey''. LLooccaallCCoommmmaanndd

Specifies a command to execute on the local machine after suc-

cessfully connecting to the server. The command string extends to the end of the line, and is executed with the user's shell. The following escape character substitutions will be performed:

`%d' (local user's home directory), `%h' (remote host name), `%l'

(local host name), `%n' (host name as provided on the command

line), `%p' (remote port), `%r' (remote user name) or `%u' (local

user name). This directive is ignored unless PPeerrmmiittLLooccaallCCoommmmaanndd has been enabled. LLooccaallFFoorrwwaarrdd Specifies that a TCP port on the local machine be forwarded over the secure channel to the specified host and port from the remote machine. The first argument must be [bindaddress:]port and the second argument must be host:hostport. IPv6 addresses can be specified by enclosing addresses in square brackets or by using an alternative syntax: [bindaddress/]port and host/hostport. Multiple forwardings may be specified, and additional forwardings can be given on the command line. Only the superuser can forward

privileged ports. By default, the local port is bound in accor-

dance with the GGaatteewwaayyPPoorrttss setting. However, an explicit bindaddress may be used to bind the connection to a specific address. The bindaddress of ``localhost'' indicates that the listening port be bound for local use only, while an empty address or `*' indicates that the port should be available from all interfaces. LLooggLLeevveell Gives the verbosity level that is used when logging messages from

ssh(1). The possible values are: QUIET, FATAL, ERROR, INFO, VER-

BOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO. DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify higher levels of verbose output. MMAACCss Specifies the MAC (message authentication code) algorithms in

order of preference. The MAC algorithm is used in protocol ver-

sion 2 for data integrity protection. Multiple algorithms must

be comma-separated. The default is:

hmac-md5,hmac-sha1,umac-64@openssh.com,

hmac-ripemd160,hmac-sha1-96,hmac-md5-96

NNooHHoossttAAuutthheennttiiccaattiioonnFFoorrLLooccaallhhoosstt This option can be used if the home directory is shared across machines. In this case localhost will refer to a different

machine on each of the machines and the user will get many warn-

ings about changed host keys. However, this option disables host authentication for localhost. The argument to this keyword must be ``yes'' or ``no''. The default is to check the host key for localhost. NNuummbbeerrOOffPPaasssswwoorrddPPrroommppttss Specifies the number of password prompts before giving up. The argument to this keyword must be an integer. The default is 3. PPaasssswwoorrddAAuutthheennttiiccaattiioonn Specifies whether to use password authentication. The argument to this keyword must be ``yes'' or ``no''. The default is ``yes''. PPeerrmmiittLLooccaallCCoommmmaanndd Allow local command execution via the LLooccaallCCoommmmaanndd option or using the !!command escape sequence in ssh(1). The argument must be ``yes'' or ``no''. The default is ``no''. PPoorrtt Specifies the port number to connect on the remote host. The default is 22. PPrreeffeerrrreeddAAuutthheennttiiccaattiioonnss Specifies the order in which the client should try protocol 2 authentication methods. This allows a client to prefer one

method (e.g. kkeeyybbooaarrdd-iinntteerraaccttiivvee) over another method (e.g.

ppaasssswwoorrdd) The default for this option is: ``gssapi-with-mic,

hostbased, publickey, keyboard-interactive, password''.

PPrroottooccooll Specifies the protocol versions ssh(1) should support in order of

preference. The possible values are `1' and `2'. Multiple ver-

sions must be comma-separated. The default is ``2,1''. This

means that ssh tries version 2 and falls back to version 1 if version 2 is not available. PPrrooxxyyCCoommmmaanndd

Specifies the command to use to connect to the server. The com-

mand string extends to the end of the line, and is executed with

the user's shell. In the command string, `%h' will be substi-

tuted by the host name to connect and `%p' by the port. The com-

mand can be basically anything, and should read from its standard input and write to its standard output. It should eventually connect an sshd(8) server running on some machine, or execute

sssshhdd -ii somewhere. Host key management will be done using the

HostName of the host being connected (defaulting to the name typed by the user). Setting the command to ``none'' disables this option entirely. Note that CChheecckkHHoossttIIPP is not available for connects with a proxy command. This directive is useful in conjunction with nc(1) and its proxy support. For example, the following directive would connect via an HTTP proxy at 192.0.2.0:

ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p

PPuubbkkeeyyAAuutthheennttiiccaattiioonn Specifies whether to try public key authentication. The argument to this keyword must be ``yes'' or ``no''. The default is ``yes''. This option applies to protocol version 2 only. RReekkeeyyLLiimmiitt Specifies the maximum amount of data that may be transmitted

before the session key is renegotiated. The argument is the num-

ber of bytes, with an optional suffix of `K', `M', or `G' to indicate Kilobytes, Megabytes, or Gigabytes, respectively. The default is between `1G' and `4G', depending on the cipher. This option applies to protocol version 2 only. RReemmootteeFFoorrwwaarrdd Specifies that a TCP port on the remote machine be forwarded over the secure channel to the specified host and port from the local machine. The first argument must be [bindaddress:]port and the second argument must be host:hostport. IPv6 addresses can be specified by enclosing addresses in square brackets or by using an alternative syntax: [bindaddress/]port and host/hostport. Multiple forwardings may be specified, and additional forwardings can be given on the command line. Only the superuser can forward privileged ports. If the bindaddress is not specified, the default is to only bind to loopback addresses. If the bindaddress is `*' or an empty

string, then the forwarding is requested to listen on all inter-

faces. Specifying a remote bindaddress will only succeed if the server's GGaatteewwaayyPPoorrttss option is enabled (see sshdconfig(5)). RRhhoossttssRRSSAAAAuutthheennttiiccaattiioonn Specifies whether to try rhosts based authentication with RSA host authentication. The argument must be ``yes'' or ``no''. The default is ``no''. This option applies to protocol version 1 only and requires ssh(1) to be setuid root. RRSSAAAAuutthheennttiiccaattiioonn Specifies whether to try RSA authentication. The argument to this keyword must be ``yes'' or ``no''. RSA authentication will

only be attempted if the identity file exists, or an authentica-

tion agent is running. The default is ``yes''. Note that this option applies to protocol version 1 only. SSeennddEEnnvv Specifies what variables from the local environ(7) should be sent to the server. Note that environment passing is only supported for protocol 2. The server must also support it, and the server must be configured to accept these environment variables. Refer to AAcccceeppttEEnnvv in sshdconfig(5) for how to configure the server.

Variables are specified by name, which may contain wildcard char-

acters. Multiple environment variables may be separated by whitespace or spread across multiple SSeennddEEnnvv directives. The default is not to send any environment variables. See PATTERNS for more information on patterns. SSeerrvveerrAAlliivveeCCoouunnttMMaaxx Sets the number of server alive messages (see below) which may be sent without ssh(1) receiving any messages back from the server. If this threshold is reached while server alive messages are being sent, ssh will disconnect from the server, terminating the session. It is important to note that the use of server alive messages is very different from TTCCPPKKeeeeppAAlliivvee (below). The server

alive messages are sent through the encrypted channel and there-

fore will not be spoofable. The TCP keepalive option enabled by

TTCCPPKKeeeeppAAlliivvee is spoofable. The server alive mechanism is valu-

able when the client or server depend on knowing when a connec-

tion has become inactive. The default value is 3. If, for example, SSeerrvveerrAAlliivveeIInntteerrvvaall (see below) is set to 15 and SSeerrvveerrAAlliivveeCCoouunnttMMaaxx is left at the default, if the server becomes unresponsive, ssh will disconnect after approximately 45 seconds. This option applies to protocol version 2 only. SSeerrvveerrAAlliivveeIInntteerrvvaall Sets a timeout interval in seconds after which if no data has been received from the server, ssh(1) will send a message through the encrypted channel to request a response from the server. The default is 0, indicating that these messages will not be sent to the server. This option applies to protocol version 2 only. SSmmaarrttccaarrddDDeevviiccee Specifies which smartcard device to use. The argument to this keyword is the device ssh(1) should use to communicate with a smartcard used for storing the user's private RSA key. By default, no device is specified and smartcard support is not activated. SSttrriiccttHHoossttKKeeyyCChheecckkiinngg If this flag is set to ``yes'', ssh(1) will never automatically

add host keys to the ~/.ssh/knownhosts file, and refuses to con-

nect to hosts whose host key has changed. This provides maximum

protection against trojan horse attacks, though it can be annoy-

ing when the /etc/sshknownhosts file is poorly maintained or when connections to new hosts are frequently made. This option forces the user to manually add all new hosts. If this flag is set to ``no'', ssh will automatically add new host keys to the user known hosts files. If this flag is set to ``ask'', new host keys will be added to the user known host files only after the user has confirmed that is what they really want to do, and ssh will refuse to connect to hosts whose host key has changed. The host keys of known hosts will be verified automatically in all cases. The argument must be ``yes'', ``no'', or ``ask''. The default is ``ask''. TTCCPPKKeeeeppAAlliivvee Specifies whether the system should send TCP keepalive messages to the other side. If they are sent, death of the connection or crash of one of the machines will be properly noticed. However,

this means that connections will die if the route is down tempo-

rarily, and some people find it annoying. The default is ``yes'' (to send TCP keepalive messages), and the client will notice if the network goes down or the remote host dies. This is important in scripts, and many users want it too. To disable TCP keepalive messages, the value should be set to ``no''. TTuunnnneell Request tun(4) device forwarding between the client and the

server. The argument must be ``yes'', ``point-to-point'' (layer

3), ``ethernet'' (layer 2), or ``no''. Specifying ``yes''

requests the default tunnel mode, which is ``point-to-point''.

The default is ``no''. TTuunnnneellDDeevviiccee Specifies the tun(4) devices to open on the client (localtun) and the server (remotetun). The argument must be localtun[:remotetun]. The devices may be specified by numerical ID or the keyword ``any'', which uses the next available tunnel device. If remotetun is not specified, it defaults to ``any''. The default is ``any:any''. UUsseePPrriivviilleeggeeddPPoorrtt

Specifies whether to use a privileged port for outgoing connec-

tions. The argument must be ``yes'' or ``no''. The default is ``no''. If set to ``yes'', ssh(1) must be setuid root. Note that this option must be set to ``yes'' for RRhhoossttssRRSSAAAAuutthheennttiiccaattiioonn with older servers.

UUsseerr Specifies the user to log in as. This can be useful when a dif-

ferent user name is used on different machines. This saves the

trouble of having to remember to give the user name on the com-

mand line. UUsseerrKKnnoowwnnHHoossttssFFiillee Specifies a file to use for the user host key database instead of ~/.ssh/knownhosts. VVeerriiffyyHHoossttKKeeyyDDNNSS Specifies whether to verify the remote key using DNS and SSHFP resource records. If this option is set to ``yes'', the client will implicitly trust keys that match a secure fingerprint from DNS. Insecure fingerprints will be handled as if this option was set to ``ask''. If this option is set to ``ask'', information on fingerprint match will be displayed, but the user will still need to confirm new host keys according to the SSttrriiccttHHoossttKKeeyyCChheecckkiinngg option. The argument must be ``yes'', ``no'', or ``ask''. The default is ``no''. Note that this option applies to protocol version 2 only. See also VERIFYING HOST KEYS in ssh(1). VViissuuaallHHoossttKKeeyy If this flag is set to ``yes'', an ASCII art representation of the remote host key fingerprint is printed additionally to the hex fingerprint string. If this flag is set to ``no'', only the hex fingerprint string will be printed. The default is ``no''. XXAAuutthhLLooccaattiioonn Specifies the full pathname of the xauth(1) program. The default is /usr/X11R6/bin/xauth. PPAATTTTEERRNNSS

A pattern consists of zero or more non-whitespace characters, `*' (a

wildcard that matches zero or more characters), or `?' (a wildcard that

matches exactly one character). For example, to specify a set of decla-

rations for any host in the ``.co.uk'' set of domains, the following pat-

tern could be used: Host *.co.uk

The following pattern would match any host in the 192.168.0.[0-9] network

range: Host 192.168.0.?

A pattern-list is a comma-separated list of patterns. Patterns within

pattern-lists may be negated by preceding them with an exclamation mark

(`!'). For example, to allow a key to be used from anywhere within an organisation except from the ``dialup'' pool, the following entry (in authorizedkeys) could be used: from="!*.dialup.example.com,*.example.com" FILES ~/.ssh/config

This is the per-user configuration file. The format of this file

is described above. This file is used by the SSH client. Because of the potential for abuse, this file must have strict

permissions: read/write for the user, and not accessible by oth-

ers. /etc/sshconfig Systemwide configuration file. This file provides defaults for those values that are not specified in the user's configuration file, and for those users who do not have a configuration file.

This file must be world-readable.