Hostid

hostid shows the numeric ID of the current host.

Provided by
Not all distributions provide this command, but most (all?) of the ones that do incorporate this from the GNU Coreutils: and use its man page

Related Commands
All of these relate to system-wide information.
 * date - set or show the time.
 * arch - show CPU hardware details.
 * nproc - Show the number of cores.
 * uname - Show host and kernel information.
 * hostname - Set or show the host's name.
 * uptime - Show system uptime and recent load averages.