GUID Partition Table

The GUID Partition Table (GPT) is a standard for the layout of partition tables of a physical computer storage device, such as a hard disk drive or solid-state drive, using universally unique identifiers, which are also known as globally unique identifiers (GUIDs). Forming a part of the Unified Extensible Firmware Interface (UEFI) standard (Unified EFI Forum-proposed replacement for the PC BIOS), it is nevertheless also used for some BIOS systems, because of the limitations of master boot record (MBR) partition tables, which use 32 bits for logical block addressing (LBA) of traditional 512-byte disk sectors.

All modern personal computer operating systems support GPT. Some, including macOS and Microsoft Windows on the x86 architecture, support booting from GPT partitions only on systems with EFI firmware, but FreeBSD and most Linux distributions can boot from GPT partitions on systems with both legacy BIOS firmware interface and EFI.


The Master Boot Record (MBR) partitioning scheme, widely used since the early 1980s, imposed limitations for use of modern hardware. A major deficiency is the limited size of 32 bits for block addresses and related information. For hard disks with 512-byte sectors, the MBR partition table entries allow a maximum size of 2 TiB (2³² × 512 bytes).[1]

In the late 1990s, Intel developed a new partition table format as part of what eventually became the Unified Extensible Firmware Interface (UEFI). As of 2010, the GUID Partition Table forms a subset of the UEFI specification.[2] GPT uses 64 bits for logical block addresses, allowing a maximum disk size of 264 sectors. For disks with 512-byte sectors, the maximum size is 9.4 ZB (9.4 × 10²¹ bytes) or 8 ZiB (264 sectors × 29 bytes per sector).[1][3]


Like modern MBRs, GPTs use logical block addressing (LBA) in place of the historical cylinder-head-sector (CHS) addressing. The protective MBR is stored at LBA 0, the GPT header is in LBA 1, and the GPT header has a pointer to the partition table (Partition Entry Array), typically at LBA 2. The UEFI specification stipulates that a minimum of 16,384 bytes, regardless of sector size, are allocated for the Partition Entry Array.[4] Each entry has a size of 128 bytes. Thus, on a disk with 512-byte sectors, sector number 34 is the first usable sector on the disk.

Hard-disk manufacturers are transitioning new products to using 4,096-byte sectors. The first such drives continued to present 512-byte physical sectors to the operating system; degraded performance could result when the drive's physical 4-KiB sector boundaries did not coincide with the 4 KiB logical blocks, clusters and virtual memory pages common in many operating systems and file systems. This was a particular problem on write operations, when the drive is forced to perform two read-modify-write operations to satisfy a single misaligned 4 KiB write operation.[5]

MBR variants

Protective MBR (LBA 0)

For limited backward compatibility, the space of the legacy MBR is still reserved in the GPT specification, but it is now used in a way that prevents MBR-based disk utilities from misrecognizing and possibly overwriting GPT disks. This is referred to as a protective MBR.[3]

A single partition type of EEh, encompassing the entire GPT drive (where "entire" actually means as much of the drive as can be represented in an MBR), is indicated and identifies it as GPT. Operating systems and tools which cannot read GPT disks will generally recognize the disk as containing one partition of unknown type and no empty space, and will typically refuse to modify the disk unless the user explicitly requests and confirms the deletion of this partition. This minimizes accidental erasures.[3] Furthermore, GPT-aware OSes may check the protective MBR and if the enclosed partition type is not of type EEh or if there are multiple partitions defined on the target device, the OS may refuse to manipulate the partition table.[6]

If the actual size of the disk exceeds the maximum partition size representable using the legacy 32-bit LBA entries in the MBR partition table, the recorded size of this partition is clipped at the maximum, thereby ignoring the rest of the disk. This amounts to a maximum reported size of 2 TiB, assuming a disk with 512 bytes per sector (see 512e). It would result in 16 TiB with 4 KiB sectors (4Kn), but since many older operating systems and tools are hard coded for a sector size of 512 bytes or are limited to 32-bit calculations, exceeding the 2 TiB limit could cause compatibility problems.[3]

Hybrid MBR (LBA 0 + GPT)

In operating systems that support GPT-based boot through BIOS services rather than EFI, the first sector may also still be used to store the first stage of the bootloader code, but modified to recognize GPT partitions. The bootloader in the MBR must not assume a sector size of 512 bytes.[3]

Partition table header (LBA 1)

GPT header format
0 (0x00)8 bytesSignature ("EFI PART", 45h 46h 49h 20h 50h 41h 52h 54h or 0x5452415020494645ULL[lower-alpha 1] on little-endian machines)
8 (0x08)4 bytesRevision (for GPT version 1.0 (through at least UEFI version 2.7 (May 2017)), the value is 00h 00h 01h 00h)
12 (0x0C)4 bytesHeader size in little endian (in bytes, usually 5Ch 00h 00h 00h or 92 bytes)
16 (0x10)4 bytesCRC32 of header (offset +0 up to header size) in little endian, with this field zeroed during calculation
20 (0x14)4 bytesReserved; must be zero
24 (0x18)8 bytesCurrent LBA (location of this header copy)
32 (0x20)8 bytesBackup LBA (location of the other header copy)
40 (0x28)8 bytesFirst usable LBA for partitions (primary partition table last LBA + 1)
48 (0x30)8 bytesLast usable LBA (secondary partition table first LBA − 1)
56 (0x38)16 bytesDisk GUID in mixed endian[6]
72 (0x48)8 bytesStarting LBA of array of partition entries (always 2 in primary copy)
80 (0x50)4 bytesNumber of partition entries in array
84 (0x54)4 bytesSize of a single partition entry (usually 80h or 128)
88 (0x58)4 bytesCRC32 of partition entries array in little endian
92 (0x5C)*Reserved; must be zeroes for the rest of the block (420 bytes for a sector size of 512 bytes; but can be more with larger sector sizes)

The partition table header defines the usable blocks on the disk. It also defines the number and size of the partition entries that make up the partition table.

Partition entries (LBA 2–33)

GUID partition entry format
0 (0x00)16 bytesPartition type GUID (mixed endian[6])
16 (0x10)16 bytesUnique partition GUID (mixed endian)
32 (0x20)8 bytesFirst LBA (little endian)
40 (0x28)8 bytesLast LBA (inclusive, usually odd)
48 (0x30)8 bytesAttribute flags (e.g. bit 60 denotes read-only)
56 (0x38)72 bytesPartition name (36 UTF-16LE code units)

After the header, the Partition Entry Array describes partitions, using a minimum size of 128 bytes for each entry block.[7] The starting location of the array on disk, and the size of each entry, are given in the GPT header. The first 16 bytes of each entry designate the partition type's globally unique identifier (GUID). For example, the GUID for an EFI system partition is C12A7328-F81F-11D2-BA4B-00A0C93EC93B. The second 16 bytes are a GUID unique to the partition. Then follow the starting and ending 64 bit LBAs, partition attributes, and the 36 character (max.) Unicode partition name. As is the nature and purpose of GUIDs and as per RFC4122[8], no central registry is needed to ensure the uniqueness of the GUID partition type designators.

The 64-bit partition table attributes are shared between 48-bit common attributes for all partition types, and 16-bit type-specific attributes:

Partition attributes
0Platform required (required by the computer to function properly, OEM partition for example, disk partitioning utilities must preserve the partition as is)
1EFI firmware should ignore the content of the partition and not try to read from it
2Legacy BIOS bootable (equivalent to active flag (typically bit 7 set) at offset +0h in partition entries of the MBR partition table)[9]
3–47Reserved for future use
48–63Defined and used by the individual partition type

Microsoft defines the type-specific attributes for basic data partition as:[10][11]

Basic data partition attributes
61Shadow copy (of another partition)
63No drive letter (i.e. do not automount)

Google defines the type-specific attributes for Chrome OS kernel as:[12]

Chrome OS kernel partition attributes
56Successful boot flag
55–52Tries remaining
51–48Priority (15: highest, 1: lowest, 0: not bootable)

Operating-system support

UNIX and Unix-like systems

Details of GPT support on UNIX and Unix-like operating systems
OS family Version or edition Platform Read and write support Boot support Note
FreeBSD Since 7.0 IA-32, x86-64, ARM Yes Yes In a hybrid configuration, both GPT and MBR partition identifiers may be used.
Linux Most of the x86 Linux distributions
Fedora 8+ and Ubuntu 8.04+[13]
IA-32, x86-64 Yes Yes New tools such as gdisk, GNU Parted,[14][15] util-linux v2.23+ fdisk,[16][17] SYSLINUX, GRUB 0.96 + patches and GRUB 2 have been GPT-enabled.
macOS Since 10.4.0 (some features since 10.4.6)[18] IA-32, x86-64, PowerPC Yes Yes Only Intel Macintosh computers can boot from GPT.
MidnightBSD Since 0.4-CURRENT IA-32, x86-64 Yes Requires BIOS In a hybrid configuration, both GPT and MBR partition identifiers may be used.
NetBSD Since 6.0[19] x86[20], x86-64[21] Yes In progress Some users describe their installation procedure with EFI[22] but the official announcement of the support has not yet been made. A semi-manual UEFI installation works on NetBSD 8.0 (-current).[23]
OpenBSD Since 5.9 x86_64 Yes Requires UEFI [24]
Solaris Since Solaris 10 IA-32, x86-64, SPARC Yes Yes [25]
HP-UX Since HP-UX 11.20 IA-64 Yes Yes [26]

Windows: 32-bit versions

Windows 7 and earlier do not support UEFI on 32-bit platforms, and therefore do not allow booting from GPT partitions.[27]

Details of GPT support on 32-bit editions of Microsoft Windows[27]
OS version Release date Platform Read or write support Boot support Note
Windows XP 2001-10-25 IA-32 No No
Windows Server 2003 2003-04-24 IA-32 No No
Windows Server 2003 SP1 2005-03-30 IA-32 Yes No MBR takes precedence in hybrid configuration.
Windows Vista 2006-07-22 IA-32 Yes No MBR takes precedence in hybrid configuration.
Windows Server 2008 2008-02-27 IA-32 Yes No MBR takes precedence in hybrid configuration.
Windows 7 2009-10-22 IA-32 Yes No MBR takes precedence in hybrid configuration.
Windows 8 2012-08-01 IA-32 Yes Requires UEFI[28] MBR takes precedence in hybrid configuration.
Windows 8.1 2013-08-27 IA-32 Yes Requires UEFI[28] MBR takes precedence in hybrid configuration.
Windows 10 2015-07-29 IA-32 Yes Requires UEFI[28] MBR takes precedence in hybrid configuration.

Windows: 64-bit versions

Details of GPT support on 64-bit editions of Microsoft Windows[27]
OS version Release date Platform Read and write support Boot support Note
Windows XP Professional x64 Edition
Windows Server 2003
2005-04-25[29] x64 Yes No MBR takes precedence in hybrid configuration.
Windows Server 2003 2005-04-25 IA-64 Yes Yes MBR takes precedence in hybrid configuration.
Windows Vista 2006-07-22 x64 Yes Requires UEFI[lower-alpha 2] MBR takes precedence in hybrid configuration.
Windows Server 2008 2008-02-27 x64 Yes Requires UEFI MBR takes precedence in hybrid configuration.
Windows Server 2008 2008-02-27 IA-64 Yes Yes MBR takes precedence in hybrid configuration.
Windows 7 2009-10-22 x64 Yes Requires UEFI[lower-alpha 3] MBR takes precedence in hybrid configuration.
Windows Server 2008 R2 2009-10-22 IA-64 Yes Yes MBR takes precedence in hybrid configuration.
Windows 8
Windows Server 2012
2012-08-01 x64 Yes Requires UEFI[28] MBR takes precedence in hybrid configuration.
Windows 8.1 2013-08-27 x64 Yes Requires UEFI[28] MBR takes precedence in hybrid configuration.
Windows 10 2015-07-29 x64 Yes Requires UEFI[28] MBR takes precedence in hybrid configuration.
Windows Server 2016 2016-10-12 x64 Yes Requires UEFI[28] MBR takes precedence in hybrid configuration.

Partition type GUIDs

Each partition has a "partition type GUID" that identifies the type of the partition and therefore partitions of the same type will all have the same "partition type GUID". Each partition also has a "partition unique GUID" as a separate entry, which as the name implies is a unique id for each partition.

Operating system Partition type Globally unique identifier (GUID)[lower-alpha 4]
N/A Unused entry 00000000-0000-0000-0000-000000000000
MBR partition scheme 024DEE41-33E7-11D3-9D69-0008C781F39F
EFI System partition C12A7328-F81F-11D2-BA4B-00A0C93EC93B
BIOS boot partition[lower-alpha 5] 21686148-6449-6E6F-744E-656564454649
Intel Fast Flash (iFFS) partition (for Intel Rapid Start technology)[30][31] D3BFE2DE-3DAF-11DF-BA40-E3A556D89593
Sony boot partition[lower-alpha 6] F4019732-066E-4E12-8273-346C5641494F
Lenovo boot partition[lower-alpha 6] BFBFAFE7-A34F-448A-9A5B-6213EB736C22
Windows Microsoft Reserved Partition (MSR) E3C9E316-0B5C-4DB8-817D-F92DF00215AE
Basic data partition[lower-alpha 7] EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
Logical Disk Manager (LDM) metadata partition 5808C8AA-7E8F-42E0-85D2-E1E90434CFB3
Logical Disk Manager data partition AF9B60A0-1431-4F62-BC68-3311714A69AD
Windows Recovery Environment DE94BBA4-06D1-4D40-A16A-BFD50179D6AC
IBM General Parallel File System (GPFS) partition 37AFFC90-EF7D-4E96-91C3-2D7AE055B174
Storage Spaces partition E75CAF8F-F680-4CEE-AFA3-B001E56EFC2D
HP-UX Data partition 75894C1E-3AEB-11D3-B7C1-7B03A0000000
Service partition E2A1E728-32E3-11D6-A682-7B03A0000000
Linux Linux filesystem data[lower-alpha 7] 0FC63DAF-8483-4772-8E79-3D69D8477DE4
RAID partition A19D880F-05FC-4D3B-A006-743F0F84911E
Root partition (x86)[34][35] 44479540-F297-41B2-9AF7-D131D5F0458A
Root partition (x86-64)[34][35] 4F68BCE3-E8CD-4DB1-96E7-FBCAF984B709
Root partition (32-bit ARM)[34][35] 69DAD710-2CE4-4E3C-B16C-21A1D49ABED3
Root partition (64-bit ARM/AArch64)[34][35] B921B045-1DF0-41C3-AF44-4C6F280D3FAE
/boot partition[34][35] BC13C2FF-59E6-4262-A352-B275FD6F7172
Swap partition[34][35] 0657FD6D-A4AB-43C4-84E5-0933C84B4F4F
Logical Volume Manager (LVM) partition E6D6D379-F507-44C2-A23C-238F2A3DF928
/home partition[34][35] 933AC7E1-2EB4-4F13-B844-0E14E2AEF915
/srv (server data) partition[34][35] 3B8F8425-20E0-4F3B-907F-1A25A76F98E8
Plain dm-crypt partition[36][37][38] 7FFEC5C9-2D00-49B7-8941-3EA10A5586B7
LUKS partition[36][37][38][39] CA7D7CCB-63ED-4C53-861C-1742536059CC
Reserved 8DA63339-0007-60C0-C436-083AC8230908
FreeBSD Boot partition 83BD6B9D-7F41-11DC-BE0B-001560B84F0F
Data partition 516E7CB4-6ECF-11D6-8FF8-00022D09712B
Swap partition 516E7CB5-6ECF-11D6-8FF8-00022D09712B
Unix File System (UFS) partition 516E7CB6-6ECF-11D6-8FF8-00022D09712B
Vinum volume manager partition 516E7CB8-6ECF-11D6-8FF8-00022D09712B
ZFS partition 516E7CBA-6ECF-11D6-8FF8-00022D09712B
Hierarchical File System Plus (HFS+) partition 48465300-0000-11AA-AA11-00306543ECAC
Apple APFS container
APFS FileVault volume container
Apple UFS container 55465300-0000-11AA-AA11-00306543ECAC
ZFS[lower-alpha 8] 6A898CC3-1DD2-11B2-99A6-080020736631
Apple RAID partition 52414944-0000-11AA-AA11-00306543ECAC
Apple RAID partition, offline 52414944-5F4F-11AA-AA11-00306543ECAC
Apple Boot partition (Recovery HD) 426F6F74-0000-11AA-AA11-00306543ECAC
Apple Label 4C616265-6C00-11AA-AA11-00306543ECAC
Apple TV Recovery partition 5265636F-7665-11AA-AA11-00306543ECAC
Apple Core Storage Container
HFS+ FileVault volume container
SoftRAID_Status B6FA30DA-92D2-4A9A-96F1-871EC6486200
SoftRAID_Scratch 2E313465-19B9-463F-8126-8A7993773801
SoftRAID_Volume FA709C7E-65B1-4593-BFD5-E71D61DE9B02
SoftRAID_Cache BBBA6DF5-F46F-4A89-8F59-8765B2727503
Boot partition 6A82CB45-1DD2-11B2-99A6-080020736631
Root partition 6A85CF4D-1DD2-11B2-99A6-080020736631
Swap partition 6A87C46F-1DD2-11B2-99A6-080020736631
Backup partition 6A8B642B-1DD2-11B2-99A6-080020736631
/usr partition[lower-alpha 8] 6A898CC3-1DD2-11B2-99A6-080020736631
/var partition 6A8EF2E9-1DD2-11B2-99A6-080020736631
/home partition 6A90BA39-1DD2-11B2-99A6-080020736631
Alternate sector 6A9283A5-1DD2-11B2-99A6-080020736631
Reserved partition 6A945A3B-1DD2-11B2-99A6-080020736631
NetBSD[40][lower-alpha 9] Swap partition 49F48D32-B10E-11DC-B99B-0019D1879648
FFS partition 49F48D5A-B10E-11DC-B99B-0019D1879648
LFS partition 49F48D82-B10E-11DC-B99B-0019D1879648
RAID partition 49F48DAA-B10E-11DC-B99B-0019D1879648
Concatenated partition 2DB519C4-B10F-11DC-B99B-0019D1879648
Encrypted partition 2DB519EC-B10F-11DC-B99B-0019D1879648
Chrome OS[41] Chrome OS kernel FE3A2A5D-4F32-41A7-B725-ACCC3285A309
Chrome OS rootfs 3CB8E202-3B7E-47DD-8A3C-7FF2A13CFCEC
Chrome OS future use 2E0A753D-9E48-43B0-8337-B15192CB1B5E
Container Linux by CoreOS[42] /usr partition (coreos-usr) 5DFBF5F4-2848-4BAC-AA5E-0D9A20B745A6
Resizable rootfs (coreos-resize) 3884DD41-8582-4404-B9A8-E9B84F2DF50E
OEM customizations (coreos-reserved) C95DC21A-DF0E-4340-8D7B-26CBFA9A03E0
Root filesystem on RAID (coreos-root-raid) BE9067B9-EA49-4F15-B4F6-F36F8C9E1818
Haiku[43] Haiku BFS 42465331-3BA3-10F1-802A-4861696B7521
MidnightBSD[44][lower-alpha 9] Boot partition 85D5E45E-237C-11E1-B4B3-E89A8F7FC3A7
Data partition 85D5E45A-237C-11E1-B4B3-E89A8F7FC3A7
Swap partition 85D5E45B-237C-11E1-B4B3-E89A8F7FC3A7
Unix File System (UFS) partition 0394EF8B-237E-11E1-B4B3-E89A8F7FC3A7
Vinum volume manager partition 85D5E45C-237C-11E1-B4B3-E89A8F7FC3A7
ZFS partition 85D5E45D-237C-11E1-B4B3-E89A8F7FC3A7
Ceph[lower-alpha 10] Journal 45B0969E-9B03-4F30-B4C6-B4B80CEFF106
dm-crypt journal 45B0969E-9B03-4F30-B4C6-5EC00CEFF106
OSD 4FBD7E29-9D25-41B8-AFD0-062C0CEFF05D
dm-crypt OSD 4FBD7E29-9D25-41B8-AFD0-5EC00CEFF05D
Disk in creation 89C57F98-2FE5-4DC0-89C1-F3AD0CEFF2BE
dm-crypt disk in creation 89C57F98-2FE5-4DC0-89C1-5EC00CEFF2BE
Block CAFECAFE-9B03-4F30-B4C6-B4B80CEFF106
Block DB 30CD0809-C2B2-499C-8879-2D6B78529876
Block write-ahead log 5CE17FCE-4087-4169-B7FF-056CC58473F9
Lockbox for dm-crypt keys FB3AABF9-D25F-47CC-BF5E-721D1816496B
Multipath OSD 4FBD7E29-8AE0-4982-BF9D-5A8D867AF560
Multipath journal 45B0969E-8AE0-4982-BF9D-5A8D867AF560
Multipath block CAFECAFE-8AE0-4982-BF9D-5A8D867AF560
Multipath block 7F4A666A-16F3-47A2-8445-152EF4D03F6C
Multipath block DB EC6D6385-E346-45DC-BE91-DA2A7C8B3261
Multipath block write-ahead log 01B41E1B-002A-453C-9F17-88793989FF8F
dm-crypt block CAFECAFE-9B03-4F30-B4C6-5EC00CEFF106
dm-crypt block DB 93B0052D-02D9-4D8A-A43B-33A3EE4DFBC3
dm-crypt block write-ahead log 306E8683-4FE2-4330-B7C0-00A917C16966
dm-crypt LUKS journal 45B0969E-9B03-4F30-B4C6-35865CEFF106
dm-crypt LUKS block CAFECAFE-9B03-4F30-B4C6-35865CEFF106
dm-crypt LUKS block DB 166418DA-C469-4022-ADF4-B30AFD37F176
dm-crypt LUKS block write-ahead log 86A32090-3647-40B9-BBBD-38D8C573AA86
dm-crypt LUKS OSD 4FBD7E29-9D25-41B8-AFD0-35865CEFF05D
OpenBSD Data partition 824CC7A0-36A8-11E3-890A-952519AD3F61
QNX Power-safe (QNX6) file system[46] CEF5A9AD-73BC-4601-89F3-CDEEEEE321A1
Plan 9 Plan 9 partition C91818F9-8025-47AF-89D2-F030D7000C2C
VMware ESX vmkcore (coredump partition) 9D275380-40AD-11DB-BF97-000C2911D1B8
VMFS filesystem partition AA31E02A-400F-11DB-9590-000C2911D1B8
VMware Reserved 9198EFFC-31C0-11DB-8F78-000C2911D1B8
Android-IA[47][48][49][50] Bootloader 2568845D-2332-4675-BC39-8FA5A4748D15
Bootloader2 114EAFFE-1552-4022-B26E-9B053604CF84
Boot 49A4D17F-93A3-45C1-A0DE-F50B2EBE2599
Recovery 4177C722-9E92-4AAB-8644-43502BFD5506
Misc EF32A33B-A409-486C-9141-9FFB711F6266
Metadata 20AC26BE-20B7-11E3-84C5-6CFDB94711E9
System 38F428E6-D326-425D-9140-6E0EA133647C
Cache A893EF21-E428-470A-9E55-0668FD91A2D9
Data DC76DDA9-5AC1-491C-AF42-A82591580C0D
Persistent EBC597D0-2053-4B15-8B64-E0AAC75F4DB1
Vendor C5A0AEEC-13EA-11E5-A1B1-001E67CA0C3C
Config BD59408B-4514-490D-BF12-9878D963F378
Factory 8F68CC74-C5E5-48DA-BE91-A0C8C15E9C80
Factory (alt)[51] 9FDAA6EF-4B3F-40D2-BA8D-BFF16BFB887B
Fastboot / Tertiary[52][53] 767941D0-2085-11E3-AD3B-6CFDB94711E9
OEM AC6D7924-EB71-4DF8-B48D-E267B27148FF
Android 6.0+ ARM Android Meta 19A710A2-B3CA-11E4-B026-10604B889DCF
Android EXT 193D1EA4-B3CA-11E4-B075-10604B889DCF
Open Network Install Environment (ONIE) Boot 7412F7D5-A156-4B13-81DC-867174929325
Config D4E6E2CD-4469-46F3-B5CB-1BFF57AFC149
PowerPC PReP boot 9E1A2D38-C612-4316-AA26-8B49521E5A8B OSes (Linux, etc.) Shared boot loader configuration[54] BC13C2FF-59E6-4262-A352-B275FD6F7172
Atari TOS Basic data partition (GEM, BGM, F32) 734E5AFE-F61A-11E6-BC64-92361F002671
VeraCrypt Encrypted data partition 8C8F8EFF-AC95-4770-814A-21994F2DBC8F

See also


  1. Adding ULL suffix to an integer constant makes it of type unsigned long long int.
  2. Only if using its service pack 1 or 2
  3. In a multi-disk setup, non-UEFI bootloader (boot drive) requires MBR-based partitioning, while a system drive can use GUID partitioning.
  4. The GUIDs in this table are written as per RFC 4122, i.e. big-endian byte order, recognizable by the position of the version bits. For example, the GUID for an EFI System partition (C12A7328-F81F-11D2-BA4B-00A0C93EC93B), when serialized in GPT data structures (little-endian), corresponds to the hex sequence 28 73 2A C1 1F F8 D2 11 BA 4B 00 A0 C9 3E C9 3B. The first three blocks are byte-swapped to little-endian, the last is a byte array. See details in TN2166[6]
  5. The formation of this GUID does not follow the GUID definition; it is formed by using the ASCII codes for the string "Hah!IdontNeedEFI". Such formation of "GUID" value breaks down the guaranteed uniqueness of GUID.
  6. Some computer manufacturers have their own GUIDs for partitions that are analogous to the EFI System Partition, but that hold boot loaders to launch manufacturer-specific recovery tools.[32]
  7. Previously, Linux used the same GUID for the data partitions as Windows (Basic data partition: EBD0A0A2-B9E5-4433-87C0-68B6B72699C7). Linux never had a separate unique partition type GUID defined for its data partitions. This created problems when dual-booting Linux and Windows in UEFI-GPT setup. The new GUID (Linux filesystem data: 0FC63DAF-8483-4772-8E79-3D69D8477DE4) was defined jointly by GPT fdisk and GNU Parted developers.[33] It is identified as type code 0x8300 in GPT fdisk. (See definitions in gdisk's
  8. The GUID for /usr on Solaris is used as a generic GUID for ZFS by macOS.
  9. NetBSD and MidnightBSD had used the FreeBSD GUIDs before their unique GUIDs were created.
  10. The Ceph filesystem uses GUIDs to mark the state of preparation a disk is in.[45]


  1. "FAQ: Drive Partition Limits" (PDF). UEFI Forum. Retrieved 2013-11-04.
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