C<value> can be NULL.
+=item $h->cp ($src, $dest);
+
+This copies a file from C<src> to C<dest> where C<dest> is
+either a destination filename or destination directory.
+
+=item $h->cp_a ($src, $dest);
+
+This copies a file or directory from C<src> to C<dest>
+recursively using the C<cp -a> command.
+
=item $result = $h->debug ($subcmd, \@extraargs);
The C<$h-E<gt>debug> command exposes some internals of
Some internal mounts are not shown.
+=item $h->mv ($src, $dest);
+
+This moves a file from C<src> to C<dest> where C<dest> is
+either a destination filename or destination directory.
+
=item $h->pvcreate ($device);
This creates an LVM physical volume on the named C<device>,