SSH_CONFIG(5)

NAME

ssh_config -- OpenSSH SSH client configuration files

SYNOPSIS

~/.ssh/config
/etc/ssh/ssh_config

DESCRIPTION

ssh(1) obtains configuration data from the following sources in the following order:
1. command-line options
2. user's configuration file (~/.ssh/config) 3. system-wide configuration file (/etc/ssh/ssh_config)
For each parameter, the first obtained value will be used. The configuration 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-specific declarations should be given near the beginning of the file, and
general defaults at the end.
Note that the Debian openssh-client package sets several options as standard in /etc/ssh/ssh_config which are not the default in ssh(1):

+o SendEnv LANG LC_*
+o HashKnownHosts yes
+o GSSAPIAuthentication yes
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 specifying configuration options using the ssh, scp, and sftp -o 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 keywords are case-insensitive and arguments are case-sensitive):
Host Restricts the following declarations (up to the next Host 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 whitespace. A single '*' as a pattern 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 matching).
See PATTERNS for more information on patterns.
AddressFamily
Specifies which address family to use when connecting. Valid
arguments are ``any'', ``inet'' (use IPv4 only), or ``inet6''
(use IPv6 only).
BatchMode
If set to ``yes'', passphrase/password querying will be disabled. In addition, the ServerAliveInterval option will be set to 300 seconds by default. This option is useful in scripts and other
batch jobs where no user is present to supply the password, and
where it is desirable to detect a broken network swiftly. The
argument must be ``yes'' or ``no''. The default is ``no''.
BindAddress
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
UsePrivilegedPort is set to ``yes''.
ChallengeResponseAuthentication Specifies whether to use challenge-response authentication. The argument to this keyword must be ``yes'' or ``no''. The default is ``yes''.
CheckHostIP
If this flag is set to ``yes'', ssh(1) will additionally check
the host IP address in the known_hosts 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''.
Cipher 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''.
Ciphers
Specifies the ciphers allowed for protocol version 2 in order of preference. Multiple ciphers must be comma-separated. The supported 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-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
aes256-cbc,arcfour
ClearAllForwardings
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 configuration files, and is automatically set by scp(1) and sftp(1). The argument must be ``yes'' or ``no''. The default is ``no''.
Compression
Specifies whether to use compression. The argument must be
``yes'' or ``no''. The default is ``no''.
CompressionLevel
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.
ConnectionAttempts
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.
ConnectTimeout
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.
ControlMaster
Enables the sharing of multiple sessions over a single network
connection. When set to ``yes'', ssh(1) will listen for connections on a control socket specified using the ControlPath argument. Additional sessions can connect to this socket using the
same ControlPath with ControlMaster 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 connections, but require confirmation using the SSH_ASKPASS program before they are accepted (see ssh-add(1) for details). If the
ControlPath cannot be opened, ssh will continue without connecting to a master instance.
X11 and ssh-agent(1) forwarding is supported over these multiplexed connections, however the display and agent forwarded will be the one belonging to the master connection i.e. it is not possible 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.
ControlPathSpecify the path to the control socket used for connection sharing as described in the ControlMaster 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
login username. It is recommended that any ControlPath used for opportunistic connection sharing include at least %h, %p, and %r. This ensures that shared connections are uniquely identified.
DynamicForward
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 [bind_address:]port. IPv6 addresses can be specified by enclosing addresses in square brackets or by using
an alternative syntax: [bind_address/]port. By default, the local port is bound in accordance with the GatewayPorts setting. However, an explicit bind_address may be used to bind the connection to a specific address. The bind_address 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.
EnableSSHKeysign
Setting this option to ``yes'' in the global client configuration file /etc/ssh/ssh_config enables the use of the helper program ssh-keysign(8) during HostbasedAuthentication. 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.
EscapeChar
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 disable the escape character entirely (making the connection transparent for binary data).
ExitOnForwardFailure
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''.
ForwardAgent
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.
ForwardX11Specifies whether X11 connections will be automatically redirected 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 display through the forwarded connection. An attacker may then be
able to perform activities such as keystroke monitoring if the
ForwardX11Trusted option is also enabled.
ForwardX11Trusted
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 considered 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 minutes. Remote clients will be refused access after this time.
The default is ``yes'' (Debian-specific).
See the X11 SECURITY extension specification for full details on the restrictions imposed on untrusted clients.
GatewayPorts
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. GatewayPorts can be used to specify 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''.
GlobalKnownHostsFile
Specifies a file to use for the global host key database instead of /etc/ssh/ssh_known_hosts.
GSSAPIAuthentication
Specifies whether user authentication based on GSSAPI is allowed. The default is ``no''. Note that this option applies to protocol version 2 only.
GSSAPIKeyExchange
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 ``no''. Note that this option applies to protocol version 2 only.
GSSAPIClientIdentity
If set, specifies the GSSAPI client identity that ssh should use when connecting to the server. The default is unset, which means that the default identity will be used.
GSSAPIDelegateCredentials Forward (delegate) credentials to the server. The default is
``no''. Note that this option applies to protocol version 2 connections using GSSAPI.
GSSAPIRenewalForcesRekey If set to ``yes'' then renewal of the client's GSSAPI credentials will force the rekeying of the ssh connection. With a compatible server, this can delegate the renewed credentials to a session on the server. The default is ``no''.
GSSAPITrustDns
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.
HashKnownHosts
Indicates that ssh(1) should hash host names and addresses when
they are added to ~/.ssh/known_hosts. These hashed names may be used normally by ssh(1) and sshd(8), but they do not reveal identifying 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). Use of this option may
break facilities such as tab-completion that rely on being able
to read unhashed host names from ~/.ssh/known_hosts.
HostbasedAuthentication
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 RhostsRSAAuthentication.
HostKeyAlgorithms
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''.
HostKeyAlias
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 database files. This option is useful for tunneling SSH connections or for multiple servers running on a single host.
HostName
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 HostName specifications).
IdentitiesOnly
Specifies that ssh(1) should only use the authentication identity files configured in the ssh_config 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''.
IdentityFile
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/id_rsa and ~/.ssh/id_dsa for protocol version 2. Additionally, any identities represented by the authentication agent will be used for authentication. ssh(1) will try to load certificate information from the filename obtained by
appending -cert.pub to the path of a specified IdentityFile.
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 configuration files; all these identities will be tried in sequence.
KbdInteractiveAuthentication Specifies whether to use keyboard-interactive authentication.
The argument to this keyword must be ``yes'' or ``no''. The
default is ``yes''.
KbdInteractiveDevices
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''.
LocalCommandSpecifies a command to execute on the local machine after successfully 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).
The command is run synchronously and does not have access to the session of the ssh(1) that spawned it. It should not be used for interactive commands.
This directive is ignored unless PermitLocalCommand has been enabled.
LocalForward
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 [bind_address:]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: [bind_address/]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 accordance with the GatewayPorts setting. However, an explicit bind_address may be used to bind the connection to a specific address. The bind_address 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.
LogLevel
Gives the verbosity level that is used when logging messages from ssh(1). The possible values are: QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3. The default is INFO.
DEBUG and DEBUG1 are equivalent. DEBUG2 and DEBUG3 each specify higher levels of verbose output.
MACs Specifies the MAC (message authentication code) algorithms inorder of preference. The MAC algorithm is used in protocol version 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
NoHostAuthenticationForLocalhost 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 warnings 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.
NumberOfPasswordPrompts
Specifies the number of password prompts before giving up. The
argument to this keyword must be an integer. The default is 3.
PasswordAuthentication
Specifies whether to use password authentication. The argument
to this keyword must be ``yes'' or ``no''. The default is
``yes''.
PermitLocalCommand
Allow local command execution via the LocalCommand option or using the !command escape sequence in ssh(1). The argument must be ``yes'' or ``no''. The default is ``no''.
PKCS11Provider
Specifies which PKCS#11 provider to use. The argument to this
keyword is the PKCS#11 shared libary ssh(1) should use to communicate with a PKCS#11 token providing the user's private RSA key.
Port Specifies the port number to connect on the remote host. The default is 22.
PreferredAuthentications Specifies the order in which the client should try protocol 2
authentication methods. This allows a client to prefer one
method (e.g. keyboard-interactive) over another method (e.g. password) The default for this option is:
``gssapi-with-mic,hostbased,publickey,keyboard-interactive,password''.
Protocol
Specifies the protocol versions ssh(1) should support in order of preference. The possible values are '1' and '2'. Multiple versions must be comma-separated. When this option is set to
``2,1'' ssh will try version 2 and fall back to version 1 if version 2 is not available. The default is '2'.
ProxyCommandSpecifies the command to use to connect to the server. The command string extends to the end of the line, and is executed with the user's shell. In the command string, '%h' will be substituted by the host name to connect and '%p' by the port. The command 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
sshd -i 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 CheckHostIP 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
PubkeyAuthentication
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.
RekeyLimit
Specifies the maximum amount of data that may be transmitted
before the session key is renegotiated. The argument is the number 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.
RemoteForward
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 [bind_address:]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: [bind_address/]port and host/hostport. Multiple forwardings may be specified, and additional forwardings can be given on the command line. Privileged ports can be forwarded only when logging in as root on the remote machine.
If the port argument is '0', the listen port will be dynamically allocated on the server and reported to the client at run time.
If the bind_address is not specified, the default is to only bind to loopback addresses. If the bind_address is '*' or an empty string, then the forwarding is requested to listen on all interfaces. Specifying a remote bind_address will only succeed if the server's GatewayPorts option is enabled (see sshd_config(5)).
RhostsRSAAuthentication
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.
RSAAuthentication
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 authentication agent is running. The default is ``yes''. Note that this
option applies to protocol version 1 only.
SendEnv
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 AcceptEnv in sshd_config(5) for how to configure the server. Variables are specified by name, which may contain wildcard characters. Multiple environment variables may be separated by
whitespace or spread across multiple SendEnv directives. The default is not to send any environment variables.
See PATTERNS for more information on patterns.
ServerAliveCountMax
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 TCPKeepAlive (below). The server alive messages are sent through the encrypted channel and therefore will not be spoofable. The TCP keepalive option enabled by TCPKeepAlive is spoofable. The server alive mechanism is valuable when the client or server depend on knowing when a connection has become inactive.
The default value is 3. If, for example, ServerAliveInterval (see below) is set to 15 and ServerAliveCountMax 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; in protocol version 1 there is no mechanism to
request a response from the server to the server alive messages, so disconnection is the responsibility of the TCP stack.
ServerAliveInterval
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, or 300 if the BatchMode option is set. This option applies to protocol version 2 only. ProtocolKeepAlives and SetupTimeOut are Debian-specific compatibility aliases for this option.
StrictHostKeyChecking
If this flag is set to ``yes'', ssh(1) will never automatically
add host keys to the ~/.ssh/known_hosts file, and refuses to connect to hosts whose host key has changed. This provides maximum protection against trojan horse attacks, though it can be annoying when the /etc/ssh/ssh_known_hosts 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''.
TCPKeepAlive
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. This
option only uses TCP keepalives (as opposed to using ssh level
keepalives), so takes a long time to notice when the connection
dies. As such, you probably want the ServerAliveInterval option as well. However, this means that connections will die if the
route is down temporarily, 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''.
Tunnel 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''.
TunnelDevice
Specifies the tun(4) devices to open on the client (local_tun) and the server (remote_tun).
The argument must be local_tun[:remote_tun]. The devices may be specified by numerical ID or the keyword ``any'', which uses the next available tunnel device. If remote_tun is not specified, it defaults to ``any''. The default is ``any:any''.
UseBlacklistedKeysSpecifies whether ssh(1) should use keys recorded in its blacklist of known-compromised keys (see ssh-vulnkey(1)) for authentication. If ``yes'', then attempts to use compromised keys for
authentication will be logged but accepted. It is strongly recommended that this be used only to install new authorized keys on the remote system, and even then only with the utmost care. If
``no'', then attempts to use compromised keys for authentication will be prevented. The default is ``no''.
UsePrivilegedPortSpecifies whether to use a privileged port for outgoing connections. 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
RhostsRSAAuthentication with older servers.
User 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 command line.
UserKnownHostsFile
Specifies a file to use for the user host key database instead of ~/.ssh/known_hosts.
VerifyHostKeyDNS
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 StrictHostKeyChecking 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).
VisualHostKey
If this flag is set to ``yes'', an ASCII art representation of
the remote host key fingerprint is printed in addition to the hex fingerprint string at login and for unknown host keys. If this
flag is set to ``no'', no fingerprint strings are printed at
login and only the hex fingerprint string will be printed for
unknown host keys. The default is ``no''.
XAuthLocation
Specifies the full pathname of the xauth(1) program. The default is /usr/bin/xauth.

PATTERNS

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 declarations for any host in the ``.co.uk'' set of domains, the following pattern 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
authorized_keys) 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 others. It may be group-writable provided that the group in question contains only the user.
/etc/ssh/ssh_config
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.

SEE ALSO

ssh(1)

AUTHORS

OpenSSH is a derivative of the original and free ssh 1.2.12 release by
Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs, re-added newer features and created OpenSSH. Markus Friedl contributed the support for SSH protocol
versions 1.5 and 2.0.
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