blkid output, some lines contain UUID and PARTUUID pairs and others only PTUUID. What do they mean?
In particular, why are two IDs required for a partition and why are some partitions identified by UUID/PARTUUID and some by PTUUID?
Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. It only takes a minute to sign up.Sign up to join this community
UUID is a filesystem-level UUID, which is retrieved from the filesystem metadata inside the partition. It can only be read if the filesystem type is known and readable.
PARTUUID is a partition-table-level UUID for the partition, a standard feature for all partitions on GPT-partitioned disks. Since it is retrieved from the partition table, it is accessible without making any assumptions at all about the actual contents of the partition. If the partition is encrypted using some unknown encryption method, this might be the only accessible unique identifier for that particular partition.
PTUUID is the UUID of the partition table itself, a unique identifier for the entire disk assigned at the time the disk was partitioned. It is the equivalent of the disk signature on MBR-partitioned disks but with more bits and a standardized procedure for its generation.
On MBR-partitioned disks, there are no UUIDs in the partition table. The 32-bit disk signature is used in place of a
PARTUUIDs are created by adding a dash and a two-digit partition number to the end of the disk signature.