Globally Unique Identifier - Non-unique GUIDs

Non-unique GUIDs

Certain GUIDs turn up again and again, both intentionally, and otherwise. In a GUID Partition Table (GPT), it's not appropriate for more than one disk to have the same Disk GUID, or for more than one partition to have the same Unique partition GUID, however it is appropriate for multiple partitions to use the same Partition type GUID. So only Linux swap partitions, and all Linux swap partitions on GPT-formatted disks can be counted on to have the GUID 0657FD6D-A4AB-43C4-84E5-0933C84B4F4F, for example.

Some flawed GUID-generating implementations rely on pseudorandom number generators that use random number seed sources that turn out to be predictable. Standard Valid GUIDs are not chosen at random; they are chosen by standardized algorithms. (See, e.g. RFC 4122.) These algorithms result in GUIDs that are more reliably unique than ones chosen using even a hypothetically perfect random number generator, and far more reliably unique than numbers chosen by pseudorandom number generators.