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{{short description|Command line utility of DOS and Microsoft Windows operating systems}}
{{lowercase title|title=fdisk}}
{{Infobox software
| name = fdisk
| logo = 
| screenshot = Fdisk.png
| screenshot size = 300px
| caption = Screenshot of FDISK on [[MS-DOS]]
| developer = Robert Baron, [[IBM]], [[Microsoft]], [[Digital Research]], [[Datalight]], [[Novell]], Brian E. Reifsnyder
| released = {{Release year|1983|03|df=yes}}
| latest release version = 
| latest release date = 
| operating system = [[MS-DOS]], [[IBM PC DOS|PC DOS]], [[FlexOS]], [[SISNE plus]], [[OS/2]], [[eComStation]], [[ArcaOS]], [[Microsoft Windows|Windows]], [[DR DOS]], [[ROM-DOS]], [[FreeDOS]], [[PTS-DOS]], *[[BSD]],<ref name=*bsd>{{cite web | url= http://mdoc.su/-/fdisk.8 | title= fdisk(8) — PC slice table (MBR) maintenance program | work= System Manager's Manual | publisher= [[FreeBSD]], [[NetBSD]], [[OpenBSD]], [[DragonFly BSD]] }}</ref> [[SysV]]
| genre = [[Command (computing)|Command]]
| license = MS-DOS, PC DOS, FlexOS, OS/2, Windows, DR DOS, ROM-DOS, PTS-DOS: [[Proprietary software|Proprietary]] [[commercial software]]<br />
FreeDOS: [[GNU GPLv2]]
| website = 
}}

'''fdisk''' is a [[command-line utility]] for [[disk partitioning]]. It has been part of [[DOS]], [[Digital Research|DR]] [[FlexOS]], [[IBM]] [[OS/2]], and early versions of [[Microsoft Windows]], as well as certain ports of [[FreeBSD]],{{r|f}} [[NetBSD]],{{r|n}} [[OpenBSD]],{{r|o}} [[DragonFly BSD]]{{r|d}} and [[macOS]]{{r|x}} for compatibility reasons. [[Windows 2000]] and its successors have replaced fdisk with a more advanced tool called [[diskpart]].

==Implementations==

===DOS===
[[IBM]] introduced the first version of fdisk (officially dubbed "Fixed Disk Setup Program") in March 1983, with the release of the [[IBM PC/XT]] computer (the first PC to store data on a [[hard disk]]) and the [[IBM PC DOS]] 2.0 operating system. fdisk version 1.0 can create one [[FAT12]] partition, delete it, change the [[active partition]], or display partition data. fdisk writes the [[master boot record]], which supports up to four partitions. The other three were intended for other operating systems such as [[CP/M-86]] and [[Xenix]], which were expected to have their own partitioning utilities.

Microsoft first added fdisk to [[MS-DOS]] in version 3.2.<ref name="RUNNINGMSDOS">{{Cite book|author-last=Wolverton|author-first=Van|title=Running MS-DOS Version 6.22 (20th Anniversary Edition), 6th Revised edition|date=2003|publisher=[[Microsoft Press]]|isbn=0-7356-1812-7}}</ref> MS-DOS versions 2.0 through 3.10 included OEM-specific partitioning tools, which may have been named fdisk.

PC DOS 3.0, released in August 1984, added support for [[FAT16]] partitions to handle larger hard disks more efficiently. PC DOS 3.30, released in April 1987, added support for [[Disk partitioning#Extended partition|extended partitions]]. (These partitions do not store data directly but can contain up to 23 [[logical drive]]s.) In both cases, fdisk was modified to work with FAT16 and extended partitions. Support for [[FAT16B]] was first added to Compaq's fdisk in MS-DOS 3.31. FAT16B later became available with MS-DOS and PC DOS 4.0.

The undocumented <code>/mbr</code> switch in fdisk, which could repair the [[master boot record]], soon became popular.

IBM PC DOS 7.10 shipped with the new fdisk32 utility.

[[ROM-DOS]],<ref>{{cite web|url=https://www.datalight.com/assets/files/ROM-DOS_Users_Guide.pdf|title=Datalight ROM-DOS User's Guide|website=www.datalight.com}}</ref> [[DR DOS 6.0]]<ref name="drdos6userguide">[https://www.4corn.co.uk/archive/docs/DR%20DOS%206.0%20User%20Guide-opt.pdf DR DOS 6.0 User Guide Optimisation and Configuration Tips]</ref> [[FlexOS]],<ref>{{Cite web |title=FlexOS User's Guide Version 1.3 |url=http://www.bitsavers.org/pdf/digitalResearch/flexos/1073-2003_FlexOS_Users_Guide_V1.3_Nov86.pdf |date=1986-11-01 |url-status=dead |archive-url=https://web.archive.org/web/20211120134812/http://www.bitsavers.org/pdf/digitalResearch/flexos/1073-2003_FlexOS_Users_Guide_V1.3_Nov86.pdf |archive-date=2021-11-20 |website=Bitsavers.og |publisher=[[Digital Research]]}}</ref> [[PTS-DOS]] 2000 Pro,<ref>{{cite web |title=PTS-DOS 2000 Pro User Manual |publisher=[[Paragon Technology GmbH]] |location=Buggingen, Germany |date=1999 |url=http://download.paragon-software.com/doc/manual_dos_eng.pdf |access-date=2018-05-12 |url-status=live |archive-url=https://web.archive.org/web/20180512094512/http://download.paragon-software.com/doc/manual_dos_eng.pdf |archive-date=2018-05-12}}</ref> and [[FreeDOS]],<ref>{{cite web|title=ibiblio.org FreeDOS Group -- FreeDOS Base|url=http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/1.2/repos/pkg-html/group-base.html|access-date=2020-06-03|website=www.ibiblio.org}}</ref> include an implementation of the fdisk command.

===Windows===
[[File:Microsoft Windows 95 Version 4.00.1111 fdisk command 492x259.png|thumb|300px|The fdisk command on [[Microsoft Windows 95]]]]

[[Windows 95]], [[Windows 98]], and  [[Windows ME]] shipped with a derivative of the MS-DOS fdisk. [[Windows 2000]] and its successors, however, came with the more advanced{{according to whom|date=January 2025}} [[diskpart]] and the graphical [[Disk Management]] utilities.

Starting with Windows 95 OSR2, fdisk supports the [[FAT32]] file system.<ref>{{cite web|url=https://support.microsoft.com/en-us/kb/255867|title=How to Use the Fdisk and Format Tools to Partition or Repartition a Hard Disk |work=Support |publisher=[[Microsoft]] |date=28 June 2012 |edition=6.0}}</ref> 

The version of fdisk that ships with Windows 95 does not report the correct size of a hard disk that is larger than 64 GB. An updated fdisk is available from Microsoft to correct this issue.<ref>{{cite web |url=https://support.microsoft.com/en-us/kb/263044 |title=Fdisk Does Not Recognize Full Size of Hard Disks Larger than 64 GB |publisher=[[Microsoft]] |date=24 August 2012 |edition=4.0 |website=Support}}</ref> In addition, fdisk cannot create partitions larger than 512 GB, even though FAT32 supports partitions as big as 2 TB. This limitation applies to all versions of fdisk supplied with Windows 95 OSR 2.1, Windows 98 and Windows ME.

===IBM OS/2===
Before version 4.0, [[OS/2]] shipped with two partition table managers. These were the [[text mode]] fdisk<ref>{{cite web |url=http://www.jatomes.com/Help/Os2Cmd.php#FDISK |title=JaTomes Help - OS/2 Commands |access-date=2019-06-20 |archive-date=2019-04-14 |archive-url=https://web.archive.org/web/20190414130029/http://www.jatomes.com/Help/Os2Cmd.php#FDISK |url-status=dead }}</ref> and the [[GUI|graphical]] fdiskpm.<ref>{{cite web |url=http://www.jatomes.com/Help/Os2Cmd.php#FDISKPM |title=JaTomes Help - OS/2 Commands |access-date=2019-06-20 |archive-date=2019-04-14 |archive-url=https://web.archive.org/web/20190414130029/http://www.jatomes.com/Help/Os2Cmd.php#FDISKPM |url-status=dead }}</ref> The two have identical functionality, and can manipulate both FAT partitions and the more advanced [[High Performance File System|HPFS]] partitions.

OS/2 4.5 and higher (including [[eComStation]] and [[ArcaOS]]) can use the [[IBM Journaled File System 2 (JFS2)|JFS]] file system, as well as FAT and HPFS. They replaced fdisk with the [[Logical Volume Manager (Linux)|Logical Volume Manager]] (LVM).

===Mach and 386BSD===
{{Anchor|FreeBSD|NetBSD|OpenBSD|DragonFly|BSD|DragonFly BSD|OS X|macOS}}
fdisk for [[Mach (kernel)|Mach Operating System]] was written by Robert Baron. It was ported to [[386BSD]] by Julian Elischer,<ref>{{cite web|url=https://www.freebsd.org/cgi/man.cgi?fdisk|title = Fdisk}}</ref> and the implementation is being used by [[FreeBSD]],<ref name=f>{{cite web |url= http://bxr.su/f/sbin/fdisk/ |title= fdisk — PC slice table maintenance utility |website= BSD Cross Reference |publisher= [[FreeBSD]]}}
*{{cite book |section=fdisk -- PC slice table maintenance utility |title=FreeBSD Manual Pages |url=http://mdoc.su/f/fdisk.8}}</ref> [[NetBSD]]<ref name=n>{{cite web |url= http://bxr.su/n/sbin/fdisk/ |title= fdisk — MS-DOS partition maintenance program |website= BSD Cross Reference |publisher= [[NetBSD]]}}</ref> and [[DragonFly BSD]],<ref name=d>{{cite web |url= http://bxr.su/d/sbin/fdisk/ |title= fdisk — PC slice table (MBR) maintenance program |website= BSD Cross Reference |publisher= [[DragonFly BSD]]}}
*{{cite book |section=fdisk - PC slice table (MBR) maintenance program |title=DragonFly On-Line Manual Pages |url=http://mdoc.su/d/fdisk.8}}</ref> all as of 2019, as well as the early versions of [[OpenBSD]] between 1995 and 1997 before OpenBSD 2.2.{{r|*bsd}}

Tobias Weingartner re-wrote fdisk in 1997 before OpenBSD 2.2,<ref name=o>{{cite web |url= http://bxr.su/o/sbin/fdisk/ |title= fdisk — partition table maintenance program |website= BSD Cross Reference |publisher= [[OpenBSD]]}}
*{{cite book |section=fdisk — partition table maintenance program |title=OpenBSD manual page server |url=http://mdoc.su/o/fdisk.8}}</ref> which has subsequently been forked by [[Apple Computer, Inc]] in 2002, and is still used as the basis for fdisk on macOS as of 2019.<ref name=x>{{citation |section-url= https://opensource.apple.com/source/diskdev_cmds/diskdev_cmds-593.221.1/fdisk.tproj/fdisk.8 |section= fdisk.tproj/fdisk.8 |url= https://opensource.apple.com/release/macos-10141.html |title= macOS 10.14.1 |publisher= [[Apple Inc.|Apple]] |access-date= 2019-04-11 |archive-date= 2019-04-11 |archive-url= https://web.archive.org/web/20190411071119/https://opensource.apple.com/release/macos-10141.html |url-status= dead }}</ref>

For native partitions, BSD systems traditionally use [[BSD disklabel]], and fdisk partitioning is supported only on certain architectures (for compatibility reasons) and only in addition to the BSD disklabel (which is mandatory).

===Linux===
In Linux, fdisk is a part of a standard package distributed by the Linux Kernel organization, [[util-linux]]. The original program was written by Andries E. Brouwer and A. V. Le Blanc and was later rewritten by Karel Zak and Davidlohr Bueso when they forked the util-linux package in 2006. An alternative, [[ncurses]]-based program, [[cfdisk]], allows users to create partition layouts via a [[text-based user interface]] (TUI).<ref>{{Cite web |last=Sharma |first=Deepesh |date=2021-02-22 |title=How to Create, Resize and Delete Linux Partitions With Cfdisk |url=https://www.makeuseof.com/how-to-create-resize-and-delete-linux-partitions-with-cfdisk/ |access-date=2023-05-15 |website=MUO |language=en}}</ref>

==See also==
* [[List of disk partitioning software]]
* [[format (command)]]
* [[GUID Partition Table]]

==References==
{{Reflist}}

==Further reading==
*{{Cite book|author-last=Wolverton|author-first=Van|title=MS-DOS Commands: Microsoft Quick Reference, 4th Revised edition|date=1990|publisher=[[Microsoft Press]]|isbn=978-1556152894}}
*{{Cite book|author1=Kathy Ivens|author2=Brian Proffit|year=1993|title=OS/2 Inside & Out|publisher=[[Osborne McGraw-Hill]]|isbn=978-0078818714}}
*{{Cite book|author1=Tim O'Reilly|author2=Troy Mott|author3=Walter Glenn|year=1999|title=Windows 98 in a Nutshell: A Desktop Quick Reference|publisher=[[O'Reilly Media|O'Reilly]]|isbn=978-1565924864|url-access=registration|url=https://archive.org/details/windows98innutsh00orei}}

==External links==
{{Wikibooks|Guide to Windows Commands}}
* [http://tldp.org/HOWTO/Partition/fdisk_partitioning.html Linux Partition HOWTO. Partitioning with fdisk]
* [https://www.die.net/doc/linux/man/man8/fdisk.8.html Linux Programmer's Manual, fdisk(8)]
* [https://git.kernel.org/cgit/utils/util-linux/util-linux.git/ fdisk from utils-linux-ng]
* [http://linux.die.net/man/8/blkid blkid - command-line utility to locate/print block device attributes ]
* [http://docs.fedoraproject.org/en-US/Fedora/17/html/System_Administrators_Guide/s2-sysinfo-filesystems-blkid.html Using the blkid Command] {{Webarchive|url=https://web.archive.org/web/20160913013722/http://docs.fedoraproject.org/en-US/Fedora/17/html/System_Administrators_Guide/s2-sysinfo-filesystems-blkid.html |date=2016-09-13 }} .
* [http://www.freebsd.org/cgi/man.cgi?fdisk FreeBSD System Manager's Manual, FDISK(8)]

{{Windows commands}}

[[Category:External DOS commands]]
[[Category:OS/2 commands]]
[[Category:Unix file system-related software]]
[[Category:Windows administration]]
[[Category:Disk partitioning software]]