OpenSSH SSH client (remote login program)

-i identity_file
        Selects a file from which the identity (private key) for public key authentication 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.  Identity files may also be specified on a per-host basis in
        the configuration file.  It is possible to have multiple -i options (and multiple identities
        specified in configuration files).  ssh will also try to load certificate information from the
        filename obtained by appending -cert.pub to identity filenames.

-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
        background.

-N      Do not execute a remote command.  This is useful for just forwarding ports (protocol version 2
        only).

-L [bind_address:]port:host:hostport
        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
        interfaces.

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
below).

If command is specified, it is executed on the remote host instead of a login shell.