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Partition type

Table inside a master boot record From Wikipedia, the free encyclopedia

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This article is about MBR partition types in IBM PC compatible systems. For GPT partition types, see GUID Partition Table § Partition type GUIDs. For Amiga RDB partition types, see Rigid Disk Block.

The partition type (or partition ID) in a partition's entry in the partition table inside a master boot record (MBR) is a byte value intended to specify the file system the partition contains or to flag special access methods used to access these partitions (e.g. special CHS mappings, LBA access, logical mapped geometries, special driver access, hidden partitions, secured or encrypted file systems, etc.).

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Overview

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Lists of assigned partition types to be used in the partition table in the MBR were originally maintained by IBM and Microsoft internally. When the market of PC operating systems and disk tools grew and liberated, other vendors had a need to assign special partition types to their products as well. As Microsoft neither documented all partition types already assigned by them nor wanted to maintain foreign assignments, third parties started to simply assign partition types on their own behalf in a mostly uncoordinated trial-and-error manner. This led to various conflicting assignments sometimes causing severe compatibility problems between certain products.[1]

Several industry experts including Hale Landis, Ralf D. Brown, Matthias R. Paul, and Andries E. Brouwer in the 1990s started to research partition types and published (and later synchronized) partition type lists in order to help document the industry de facto standard and thereby reduce the risk of further conflicts. Some of them also actively helped to maintain software dealing with partitions to work with the updated lists, indicated conflicts, devised additional detection methods and work-arounds for vendors, or engaged in coordinating new non-conflictive partition type assignments as well.

It is up to an operating system's boot loader or kernel how to interpret the value. So the table specifies which operating systems or disk-related products introduced an ID and what file system or special partition type they mapped it to. Partitions with partition types unknown to the software should be treated as reserved but occupied disk storage space which should not be dealt with by the software, save for partition managers.

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Local or Experimental Use

While the list is not officially maintained,[1] new assignments should be coordinated.

In particular temporary partition type assignments for local or experimental projects can utilize type 7Fh in order to avoid conflicts with already assigned types. This type was specially reserved for individual use as part of the Alternative OS Development Partition Standard (AODPS) initiative since 2002.[2]

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List of partition IDs

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This is a list of known master boot record partition types on IBM PC compatible computers:

More information Occurrence, Access ...
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See also

Notes

  1. [N 1]
    MS-DOS/PC DOS 2.0-3.1 cannot cope with hard disk partitions outside the first 32 MB of the disk. Therefore, FAT12 and FAT16 volumes in primary partitions physically residing outside this area must not use partition IDs 01h and 04h, even if they were otherwise small enough to be recognized by these DOS versions. In order to hide these volumes from these DOS issues 06h can be used instead. DOS distinguishes FAT types by their number of clusters, not by their partition ID, therefore, this does not cause any problems for DOS 3.31 and higher except for a possibly wrong file system type display in FDISK.
  2. [N 2]
    QNX partition IDs 07h, 08h, 09h, 4Dh (77), 4Eh (78), 4Fh (79), as well as B1h (177), B2h (178) and B3h (179).
  3. [N 3]
    Known partition IDs for logical sectored FATs include: 08h (Commodore MS-DOS 3.x), 11h (Leading Edge MS-DOS 3.x), 14h (AST MS-DOS 3.x), 24h (NEC MS-DOS 3.30), 56h (AT&T MS-DOS 3.x), E5h (Tandy MS-DOS), F2h (Sperry IT MS-DOS 3.x, Unisys MS-DOS 3.3 — also used by Digital Research DOS Plus 2.1). While non-standard and sub-optimal these FAT variants are perfectly valid according to the specifications of the file system itself, although default issues of MS-DOS / PC DOS 3.x were not able to cope with them. Most of these vendor specific FAT12 and FAT16 variants can be mounted by more flexible file system implementations in operating systems such as DR-DOS simply by changing the partition ID to one of the recognized types. Also, if they no longer need to be recognized by their original operating systems, existing partitions can be "converted" into FAT12 and FAT16 volumes compliant with versions of MS-DOS/PC DOS like 5.0-6.3, which do not support logical sector sizes different from 512 bytes, by switching to a BPB with 32-bit entry for the number of sectors, as introduced since DOS 3.31, keeping the cluster size and reducing the logical sector size in the BPB down to 512 bytes, while at the same time increasing the counts of logical sectors per cluster, reserved logical sectors, total logical sectors, and logical sectors per FAT by the same factor.
  4. [N 4]
    Used by OS/2 Boot Manager: 0Ah, 11h, 14h, 15h, 16h, 17h, 1Bh, 1Ch, 1Eh, 1Fh.
  5. [N 5]
    HP Volume Expansion is a variant of SpeedStor and uses partition IDs 21h, A1h, A3h, A4h, A6h, B1h, B3h, B4h, and B6h.
  6. [N 6]
    SpeedStor is an extended storage support driver for DOS for IBM PC/XT (v. 6.03) and IBM PC/AT (v. 6.5). Its custom partition types are E1h, E4h and F4h which can be marked read-only (becoming E3h, E6h, F6h), hidden (61h, 64h, 74h) or hidden read-only (63h, 66h, 76h).
  7. [N 7]
    Used by Free FDISK of FreeDOS: 8Dh, 90h, 91h, 92h, 97h, 98h, 9Ah, 9Bh.
  8. [N 8]
    Apple Mac OS X uses partition IDs A8h, ABh, ACh, and AFh.
  9. [N 9]
    Versions of DR DOS 6.0 and higher use several of these partition IDs for secured FAT partitions with single-user security: C0h, C1h, C4h, C5h, C6h, CBh, CCh, CEh, CFh.
  10. [N 10]
    Versions of IMS REAL/32 use partition IDs C0h and D0h for multi-user security.
  11. [N 11]
    Versions of Multiuser DOS use these partition IDs for secured FAT partitions with multi-user security: D0h, D1h, D4h, D5h, D6h.
  12. [N 12]
    Was suggested in now-superseded T13 EDD 4 proposal e09127r1 Archived 2017-08-19 at the Wayback Machine (2009). The successor e09127r3 Archived 2018-05-01 at the Wayback Machine (2010) now recommends to use a normal partition type (the one that a legacy OS would see) instead of this special value.
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