uuidgen vem do libuuid, que faz parte do e2fsprogs
A página de manual para a função e2fsprogs uuid_generate declara:
The uuid will be generated based on high-quality randomness from /dev/urandom, if available. If it is not available, then uuid_generate will use an alternative algorithm which uses the current time, the local ethernet MAC address (if available), and random data generated using a pseudo-random generator.