Backup pg_shadow

How can I easily backup the table pg_shadow
or at least how can I backup the data about the users of
the DB?

Ciao
Gaetano

--
#exclude <windows>
#include <CSRSS>
printf("\t\t\b\b\b\b\b\b");.
printf("\t\t\b\b\b\b\b\b");