OpenSSH SSH client (remote login program)
-f Requests ssh to go to background just before command execution. This is useful if ssh is going to
ask for passwords or passphrases, but the user wants it in the background. This implies -n. The
recommended way to start X11 programs at a remote site is with something like ssh -f host xterm.
If the ExitOnForwardFailure configuration option is set to “yes”, then a client started with -f
will wait for all remote port forwards to be successfully established before placing itself in the
-N Do not execute a remote command. This is useful for just forwarding ports (protocol version 2
-v Verbose mode. Causes ssh to print debugging messages about its progress. This is helpful in
debugging connection, authentication, and configuration problems. Multiple -v options increase the
verbosity. The maximum is 3.
Specifies that the given port on the local (client) host is to be forwarded to the given host and
port on the remote side. This works by allocating a socket to listen to port on the local side,
optionally bound to the specified bind_address. Whenever a connection is made to this port, the
connection is forwarded over the secure channel, and a connection is made to host port hostport
from the remote machine. Port forwardings can also be specified in the configuration file. IPv6
addresses can be specified by enclosing the address in square brackets. 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
ssh connects and logs into the specified hostname (with optional user name). The user must prove his/her
identity to the remote machine using one of several methods depending on the protocol version used (see
If command is specified, it is executed on the remote host instead of a login shell.