The primary (eth0 in Linux) that the machine shipped with (not so unreasonable for Suns), or that was installed at the time the license key was generated. An alternative might be a hard disk serial number, except that low-level system calls are probably needed in order to get it.
The only solution would be generating /etc/hostid during install. It can be populated by last four bytes of eth0 (as detected during install), or some randomly generated bytes (if there's no network interfaces detected during install).
Of course, there's still problem what to return if user deletes /etc/hostid file ;-)
-- Aleksandar Milivojevic <amilivojevic@xxxxxx> Pollard Banknote Limited Systems Administrator 1499 Buffalo Place Tel: (204) 474-2323 ext 276 Winnipeg, MB R3T 1L7
