Acronym for GUID Partition Table

GPT was introduced for iA64 systems, to get around a fixed 32 bit issue (2 to the power of 32 is 4 billion times a 512 byte block equals 2 Terabytes) in the PC-BIOS Partition table. Partitions larger than 2 TB require using a GPT disklabel, which differs from the PC-BIOS Partition table in a number of ways:

• Is easily extensible.
• Can contain up to 128 primary partitions, as opposed to 4, so there's no need for extended partitions.
• Allows Partitions larger than 2 TB.
• Identifies Partitions with a GUID so you can reference that Partition even if disks are moved around.
• Identifies Partition type with a GUID, thus avoiding the type conflicts that plague the PC-BIOS Partition table format.
• Provides a 46(?) character UTF-16 partition label to identify Partitions.
• Has a "fake" MBR for backwards compatibility.
• Includes a CRC32 to detect corrupt Partition tables.
• Stores a backup Partition table at the end of the disk.

Most partitioning tools under Linux will fail to do anything sensible with a > 2 TB Partition. As of this writing, parted(8) is the only one that understands them and will let you set the GPT label on the disk.

There is a lot of information stating that you cannot boot off a GPT enabled device. Most of the claims imply that the fault is with LILO or GRUB not understanding GPT devices. We've not tested this, but GPT and traditional MBRs will coexist.

See also:

• Disk Sectors on GPT Disks from the MS Knowledge Base