OK. So why don't you simply check for a second partition if the first is FAT16? It it always there, has a label of "ASTURW" and it is ext2.
If you like, you can also check for AstLinux: if "/etc/astlinux-release" exists, the system is running AstLinux. With version 2.28 the license system worked fine on all of my customer boxes. Can it have to to with 32-/64-bit, we recently switched new systems to 64-bit?
Can you not check for the MAC-address of the NIC instead? This is static.
The revoke script would need a working internet connection, right? But sometimes the customer reboots because of problems with the internet, so this would not be a foolproof solution.
The partition UUIDs stay always the same after rebooting or upgrading (UUIDs faked):
blkid
/dev/sda1: SEC_TYPE="msdos" LABEL="RUNNIX" UUID="abcd-efg" TYPE="vfat"
/dev/sda2: LABEL="ASTURW" UUID="12345-67890" TYPE="ext2"
/dev/sda3: LABEL="ASTKD" UUID="23456-78901" TYPE="ext2"
Michael