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SSH_CONFIG(5)               BSD File Formats Manual              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 decla-
     rations 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 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 keyword) 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.  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".

     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 protocol version 1.
             Currently, "blowfish", "3des", and "des" are supported.  des is only sup-
             ported 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,
                aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,
                aes256-cbc

     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 for-
             wardings 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 argu-
             ment 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 con-
             nection.

     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 connec-
             tions, 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 confir-
             mation like the "ask" option.

     ControlPath
             Specify 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.

     ControlPersist
             When used in conjunction with ControlMaster, specifies that the master con-
             nection should remain open in the background (waiting for future client con-
             nections) after the initial client connection has been closed.  If set to
             "no", then the master connection will not be placed into the background, and
             will close as soon as the initial client connection is closed.  If set to
             "yes", then the master connection will remain in the background indefinitely
             (until killed or closed via a mechanism such as the ssh(1) "-O exit" option).
             If set to a time in seconds, or a time in any of the formats documented in
             sshd_config(5), then the backgrounded master connection will automatically
             terminate after it has remained idle (with no client connections) for the
             specified time.

     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 con-
             nect 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 inter-
             faces.

             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) dur-
             ing HostbasedAuthentication.  The argument must be "yes" or "no".  The
             default is "no".  This option should be placed in the non-hostspecific sec-
             tion.  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, '^' fol-
             lowed 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 argu-
             ment 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.

     ForwardX11
             Specifies 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 monitor-
             ing 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 "no".

             See the X11 SECURITY extension specification for full details on the restric-
             tions 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 con-
             necting 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 dele-
             gate 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 GSS-
             API.

     GSSAPIKexAlgorithms
             The list of key exchange algorithms that are accepted by GSSAPI key exchange.
             Possible values are

                gss-group1-sha1-,
                gss-group14-sha1-,
                gss-gex-sha1-

             The default is "gss-group1-sha1-,gss-group14-sha1-,gss-gex-sha1-".  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).

     HostbasedAuthentication
             Specifies whether to try rhosts based authentication with public key authen-
             tication.  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-cert-v01 AT openssh.com,ssh-dss-cert-v01 AT openssh.com,
                ssh-rsa-cert-v00 AT openssh.com,ssh-dss-cert-v00 AT openssh.com,
                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 run-
             ning on a single host.

     HostName
             Specifies the real host name to log into.  This can be used to specify nick-
             names or abbreviations for hosts.  The default is the name given on the com-
             mand 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 con-
             figured 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 DSA, ECDSA or DSA authentication iden-
             tity is read.  The default is ~/.ssh/identity for protocol version 1, and
             ~/.ssh/id_dsa, ~/.ssh/id_ecdsa and ~/.ssh/id_rsa 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".

     KexAlgorithms
             Specifies the available KEX (Key Exchange) algorithms.  Multiple algorithms
             must be comma-separated.  The default is
             "diffie-hellman-group-exchange-sha256", "diffie-hellman-group-exchange-sha1",
             "diffie-hellman-group14-sha1", "diffie-hellman-group1-sha1".

     LocalCommand
             Specifies a command to execute on the local machine after successfully con-
             necting 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 sub-
             stitutions 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 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 for-
             wardings 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" indi-
             cates that the listening port be bound for local use only, while an empty
             address or '*' indicates that the port should be available from all inter-
             faces.

     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 in order of pref-
             erence.  The MAC algorithm is used in protocol version 2 for data integrity
             protection.  Multiple algorithms must be comma-separated.  The default is:

                   hmac-sha1,umac-64 AT openssh.com,
                   hmac-ripemd160,hmac-sha1-96,
                   hmac-sha2-256,hmac-sha2-512

     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 key-
             word must be "yes" or "no".  The default is to check the host key for local-
             host.

     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 key-
             word 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
             used for storing the user's private RSA key.  By default, no device is speci-
             fied and PKCS#11 support is not activated.

     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-sepa-
             rated.  The default is "2,1".  This means that ssh tries version 2 and falls
             back to version 1 if version 2 is not available.

     ProxyCommand
             Specifies 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 eventu-
             ally 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 com-
             mand 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 ses-
             sion 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 for-
             wardings 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 forward-
             ing 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 authenti-
             cation.  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.  Note that the TERM environment variable is
             always sent whenever a pseudo-terminal is requested as it is required by the
             protocol.  Refer to AcceptEnv in sshd_config(5) for how to configure the
             server.  Variables are specified by name, which may contain wildcard charac-
             ters.  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 with-
             out 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.

     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.  This option applies to protocol
             version 2 only.

     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.  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".

     UsePrivilegedPort
             Specifies 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 different 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 charac-
     ter).  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 poten-
             tial for abuse, this file must have strict permissions: read/write for the
             user, and not accessible by others.

     /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 con-
     tributed the support for SSH protocol versions 1.5 and 2.0.

BSD                            December 12, 2017                           BSD

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