Get or set a unique 32-bit identifier for the current machine. The 32-bit
identifier is intended to be unique among all UNIX systems in existence. This
normally resembles the Internet address for the local machine, as returned by
gethostbyname(3), and thus usually never needs to be set.
The sethostid call is restricted to the superuser.
The hostid argument is stored in the file /etc/hostid.