PermitRootLogin
Specifies whether the root can log in using ssh(1). The argument
must be ``yes'', ``without-password'' or ``no''. The default is
``yes''. If this options is set to ``without-password'' only
password authentication is disabled for root.
Root login with RSA authentication when the command option has
been specified will be allowed regardless of the value of this
setting (which may be useful for taking remote backups even if
root login is normally not allowed).