software-generated UUID. Store the result in /etc/hostid and use it in
the future. Perform simple UUID format check, as there is a lot of
hardware with broken UUIDs. The check should be improved to also eliminate
fake UUIDs like 00000000-0000-0000-0000-000000000000.
Requested by: many
UUID and stores it in /etc/hostid ($hostid_file) as well as sets kern.hostuuid
and kern.hostid sysctls on every boot.
Hostid can be reset using '/etc/rc.d/hostid reset' command.
Hostid generation and setting can be turned off by setting variable
hostid_enable to "NO" in /etc/rc.conf.
Reviewed by: mlaier, rink, brooks, rwatson
