C<value> can be NULL.
+=head2 download
+
+ download remotefilename (filename|-)
+
+Download file C<remotefilename> and save it as C<filename>
+on the local machine.
+
+C<filename> can also be a named pipe.
+
+See also C<upload>, C<cat>.
+
+Use C<-> instead of a filename to read/write from stdin/stdout.
+
=head2 exists
exists path
Some internal mounts are not unmounted by this call.
+=head2 upload
+
+ upload (filename|-) remotefilename
+
+Upload local file C<filename> to C<remotefilename> on the
+filesystem.
+
+C<filename> can also be a named pipe.
+
+See also C<download>.
+
+Use C<-> instead of a filename to read/write from stdin/stdout.
+
=head2 vgcreate
vgcreate volgroup physvols,...