fdisk

partition maintenance program

fdisk [options] device


       fdisk -l [device …]



Interactive program for creation and manipulation of partition tables (noninteractive version).

Block devices (Disks, RAM drive) can be divided into one or more logical disks called partitions, recorded in the partition table, usually found in sector 0 of the disk and duplicated elsewhere. (Aka `disk slices' and a `disklabel'.)

First, last, sectors and sizes can be specified by the +size{M,G,…} notation

   m   print this menu,        
   i  information about a partition   

Command (m for help): i
Partition number (1-3, default 3): 3

         Device: /dev/mmcblk0p3
          Start: 31117312
            End: 62333951
        Sectors: 31216640
      Cylinders: 487761
           Size: 14.9G
             Id: 83
           Type: Linux
    Start-C/H/S: 832/0/1
      End-C/H/S: 143/3/16
 
   p  print
Disk /dev/mmcblk0: 29.7 GiB, 31914983424 bytes, 62333952 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xc5b4c492  Seems to be randomly generated so each disk is unique

Device         Boot    Start      End  Sectors  Size Id Type
/dev/mmcblk0p1          8192    93236    85045 41.5M  c W95 FAT32 (LBA)
/dev/mmcblk0p2         94208 31116287 31022080 14.8G 83 Linux
/dev/mmcblk0p3      31117312 62333951 31216640 14.9G 83 Linux

   v  verify  
Remaining 1995 unallocated 512-byte sectors.

   F  list free space,   
Unpartitioned space /dev/mmcblk0: 3 MiB, 3145728 bytes, 6144 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes

Start   End Sectors Size
 2048  8191    6144   3M

   n   add new
   t  change type
   d  delete 
   l  list known types 
 0  Empty           24  NEC DOS         81  Minix / old Lin bf  Solaris        
 1  FAT12           27  Hidden NTFS Win 82  Linux swap / So c1  DRDOS/sec (FAT-
 2  XENIX root      39  Plan 9          83  Linux           c4  DRDOS/sec (FAT-
 3  XENIX usr       3c  PartitionMagic  84  OS/2 hidden or  c6  DRDOS/sec (FAT-
 4  FAT16 <32M      40  Venix 80286     85  Linux extended  c7  Syrinx         
 5  Extended        41  PPC PReP Boot   86  NTFS volume set da  Non-FS data    
 6  FAT16           42  SFS             87  NTFS volume set db  CP/M / CTOS / .
 7  HPFS/NTFS/exFAT 4d  QNX4.x          88  Linux plaintext de  Dell Utility   
 8  AIX             4e  QNX4.x 2nd part 8e  Linux LVM       df  BootIt         
 9  AIX bootable    4f  QNX4.x 3rd part 93  Amoeba          e1  DOS access     
 a  OS/2 Boot Manag 50  OnTrack DM      94  Amoeba BBT      e3  DOS R/O        
 b  W95 FAT32       51  OnTrack DM6 Aux 9f  BSD/OS          e4  SpeedStor      
 c  W95 FAT32 (LBA) 52  CP/M            a0  IBM Thinkpad hi ea  Rufus alignment
 e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a5  FreeBSD         eb  BeOS fs        
 f  W95 Ext'd (LBA) 54  OnTrackDM6      a6  OpenBSD         ee  GPT            
10  OPUS            55  EZ-Drive        a7  NeXTSTEP        ef  EFI (FAT-12/16/
11  Hidden FAT12    56  Golden Bow      a8  Darwin UFS      f0  Linux/PA-RISC b
12  Compaq diagnost 5c  Priam Edisk     a9  NetBSD          f1  SpeedStor      
14  Hidden FAT16 <3 61  SpeedStor       ab  Darwin boot     f4  SpeedStor      
16  Hidden FAT16    63  GNU HURD or Sys af  HFS / HFS+      f2  DOS secondary  
17  Hidden HPFS/NTF 64  Novell Netware  b7  BSDI fs         fb  VMware VMFS    
18  AST SmartSleep  65  Novell Netware  b8  BSDI swap       fc  VMware VMKCORE 
1b  Hidden W95 FAT3 70  DiskSecure Mult bb  Boot Wizard hid fd  Linux raid auto
1c  Hidden W95 FAT3 75  PC/IX           bc  Acronis FAT32 L fe  LANstep        
1e  Hidden W95 FAT1 80  Old Minix       be  Solaris boot    ff  BBT             
   u   change display/entry units 

   w  write table to disk and exit      q  quit without saving changes

   Create a new label: g GPT, G SGI (IRIX) , o DOS , s  Sun 

   O   output sfdisk script, I input script 
  DOS (MBR Master BOot Record):
   a  toggle a bootable flag,  b  edit nested BSD disklabel,  c toggle the dos compatibility flag

 x  extra functionality (experts only)
  DOS (MBR) b   move beginning of data in a partition, i   change the disk identifier (Randomly generated)
   d   display raw data of the first sector
   D   display raw data of the disklabel 
   f   fix partitions order
   c   change number of cylinders,      h   change number of heads,   s  change number of sectors/track bad ideas

`-B --protect-boot`	Don't erase the begining of the first sector when creatiing a new disk label. (for GPT and MBR.)
`-c --compatibility[dos\|nondos]`	Default `nondos`. `mode` cannot be separated from `-c` by a space, the correct short form is `-c=dos`.
`-h --help`	Display a help text and exit.
`-L --color [auto\|never\|always]`	Colorize the output.
`-l --list`	List the partition tables then exit. , Default devices from `/proc/partitions` sudo fdisk -l /dev/mmcblk0 Disk /dev/mmcblk0: 29.7 GiB, 31914983424 bytes, 62333952 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0xc5b4c492 Device Boot Start End Sectors Size Id Type /dev/mmcblk0p1 8192 93236 85045 41.5M c W95 FAT32 (LBA) /dev/mmcblk0p2 94208 31116287 31022080 14.8G 83 Linux /dev/mmcblk0p3 31117312 62333951 31216640 14.9G 83 Linux See partx for various output formats.
`-o --output list`	output columns to display. `--help` shows supported columns. The default list of columns may be extended if list is specified in the format `+list` (e.g. -o +UUID).
`-t --type type`	support only for disklabels of `type`
`-u --units[=sectors\|cylinders]`	show size units . default is sectors. `unit` cannot be separated from `-u` by a space, example `-u=cylinders`.
`-s --getsz`	size in 512-byte sectors . DEPRECATED in favour of blockdev(1).
`-C --cylinders n`	number of cylinders of the disk.
`-H --heads n`	Not the physical number, the number used for partition tables.)
`-S --sectors n`	number of sectors per track of the disk. (Not the physical number, but the number used for partition tables.) A reasonable value is 63.
`-b --sector-size bytes`	sector size of the disk. Valid values are 512, 1024, 2048, and 4096. fdisk differentiates between logical and physical sector size. This option changes both sector sizes to sectorsize.
`-w --wipe auto\| never\| always`	Wipe filesystem, RAID and partition-table signatures to avoid collisions. default `auto`, in which case signatures are wiped only when in interactive mode. In all cases detected signatures are reported by warning messages before a new partition table is created. See wipefs
`-W --wipe-partition auto\| never\| always`	Wipe filesystem, RAID and partition-table signatures from a newly created partitions, in order to avoid possible collisions. default `auto,` in which case signatures are after confirmation by user. In all cases detected signatures are reported by warning messages before a new partition is created. See wipefs
`-V --version`	Display version information and exit. fdisk from util-linux 2.29.2 fdisk -h Usage: sudo fdisk [options] change partition table sudo fdisk [options] -l [] list partition table(s) Display or manipulate a disk partition table. Options: -b, --sector-size physical and logical sector size -B, --protect-boot don't erase bootbits when creating a new label -c, --compatibility[=] mode is 'dos' or 'nondos' (default) -L, --color[=] colorize output (auto, always or never) colors are enabled by default -l, --list display partitions and exit -o, --output output columns -t, --type recognize specified partition table type only -u, --units[=] display units: 'cylinders' or 'sectors' (default) -s, --getsz size in 512-byte sectors [DEPRECATED] --bytes print SIZE in bytes -w, --wipe wipe signatures (auto, always or never) -W, --wipe-partitions wipe signatures from new partitions (auto, always or never) -C, --cylinders specify the number of cylinders -H, --heads specify the number of heads -S, --sectors specify the number of sectors per track -h, --help display this help and exit -V, --version output version information and exit Available columns (for -o): gpt: Device Start End Sectors Size Type Type-UUID Attrs Name UUID dos: Device Start End Sectors Cylinders Size Type Id Attrs Boot End-C/H/S Start-C/H/S bsd: Slice Start End Sectors Cylinders Size Type Bsize Cpg Fsize sgi: Device Start End Sectors Cylinders Size Type Id Attrs sun: Device Start End Sectors Cylinders Size Type Id Flags For more details see fdisk(8).

Mac os

With no arguments displays partition table and exits.
Example with Rasbperry Pi SD card:

> sudo fdisk  /dev/disk2 
Disk: /dev/disk2    geometry: 966/255/63 [15523840 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: 0C   64   0   1 - 1023   3  32 [      8192 -     524288] Win95 FAT32L
 2: 83 1023   3  32 - 1023   3  32 [    532480 -    7790592] Linux files*
 3: 00    0   0   0 -    0   0   0 [         0 -          0] unused      
 4: 00    0   0   0 -    0   0   0 [         0 -          0] unused

No Disk identifier: is displayed!

 sudo /usr/sbin/fdisk -d /dev/disk2    
1,63037439,0xEE,-,1023,254,63,1023,254,63
0,0,0x00,-,0,0,0,0,0,0
0,0,0x00,-,0,0,0,0,0,0
0,0,0x00,-,0,0,0,0,0,0

usage: fdisk [-ieu] [-f mbrboot] [-c cyl -h head -s sect] [-S size] [-r] [-a style] disk
    -i: initialize disk with new MBR
    -u: update MBR code, preserve partition table
    -e: edit MBRs on disk interactively
    -f: specify non-standard MBR template
    -chs: specify disk geometry
    -S: specify disk size
    -r: read partition specs from stdin (implies -i)
    -a: auto-partition with the given style
    -d: dump partition table
    -y: don't ask any questions
    -t: test if disk is partitioned
`disk' is of the form /dev/rdisk0.
auto-partition styles:
  boothfs     8Mb boot plus HFS+ root partition (default)
  hfs         Entire disk as one HFS+ partition
  dos         Entire disk as one DOS partition
  raid        Entire disk as one 0xAC partition

fdisk: 1> help
    manual      Show entire man page for fdisk
    reinit      Re-initialize loaded MBR (to defaults)
    auto        Auto-partition the disk with a partition style
    setpid      Set the identifier of a given table entry
    disk        Edit current drive stats
    edit        given table entry
    erase       Erase current MBRbootable
    update      machine code in loaded MBR
    select      extended partition table entry MBR
    print       Print loaded MBR partition table
    write       Write loaded MBR to disk
    exit,
    abort       without saving current changes

quit saving current changes

sudo fdisk -e /dev/disk2 # Attempt to examine SD card for Raspberry Pi
fdisk: could not open MBR file /usr/standalone/i386/boot0: No such file or directory

device example /dev/sda. refers to the entire disk.

partition is a device name followed by a partition number. For example, /dev/sda1 is the first partition on the first hard disk

size The "last sector" accepts size specified by number of sectors or by +size{K,B,M,G,…} notation.
If the size is prefixed by '+' it is interpreted as relative to the partition first sector in bytes, unless . followed by the suffixes K==KB==KiB=1024, M==MB==MiB=1024*1024,…

Scripts

fdisk can read (by I command) sfdisk scripts which are applied to in-memory partition table allowing modifification before write it using command O.

DISK LABELS

GPT (GUID Partition Table) the modern standard for the layout of the partition table. The first sector is reserved for a protective MBR. GPT is always a better choice than MBR, especially on modern hardware with a UEFI boot loader.
MBR A DOS-type partition table. There are 4 primary partitions. One may be an extended partition; this is a container holding logical partitions. The four primary partitions are numbered 1-4. Logical partitions always start with 5.

ENVIRONMENT

`$FDISK_DEBUG=all`	enables fdisk debug output.
`$LIBFDISK_DEBUG=all`	enables libfdisk debug output.
`$LIBBLKID_DEBUG=all`	enables libblkid debug output.
`$LIBSMARTCOLS_DEBUG=all`	enables libsmartcols debug output.
`$LIBSMARTCOLS_DEBUG_PADDING=on`	use visible padding characters. Requires enabled LIBSMARTCOLS_DEBUG.

Errors

Specifing an nonexistant disk reports:

fdisk: /dev/disk6: No such file or directory

non interactive format

if sector 0 is not valid a boot sector. fdisk initialises the boot code as well as the partition table, all four partitions will be marked empty.

The flags -a, -i or -u are used to indicate that the partition data is to be updated.

Calculates the correct cylinder, head, and sector values for partitions you edit. If you specify -v you will be asked whether you want to specify them.

When all the data for the first sector has been accumulated, fdisk will ask if you really want to write the new partition table. Only if you reply affirmatively to this question will fdisk write anything to the disk.

`-0`	Update partition slot 0.
`-1`	Update partition slot 1.
`-2`	Update partition slot 2.
`-3`	Update partition slot 3.
`-a`	Change the active partition. In interactive mode this question will be asked after the partitions have been processed.
`-b` `cylinders/heads/sectors`	Specify the BIOS parameters for `cylinders`, `heads`, and `sectors`. It is used only in conjunction with the `-u` flag.
`-B`	On an i386 or amd64 system, interactively update the boot selector settings. (The boot selector permits the user to interactively select the boot partition, and thus which operating system is run, at system boot time. See mbr(8) for more information.)
`-c` `bootcode`	Specify the filename that `fdisk` should read the bootcode from. If the name of a directory is specified, then `fdisk` will look for files with the default names in that directory. The default is to read from `/usr/mdec/mbr`, `/usr/mdec/mbr_bootsel` or `/usr/mdec/mbr_ext` depending on whether `bootmenu` was specified for any partitions on an i386 machine, and leave the bootcode empty for other machines.
`-E` `number`	Update extended partition `number`. If the specified extended partition doesn't exist an additional extended partition will be created.
`-f`	Run `fdisk` in a non-interactive mode. In this mode, you can only change the disk parameters by using the `-b` flag. This is provided only so scripts or other programs may use `fdisk` as part of an automatic installation process. Using the `-f` flag with `-u` makes it impossible to specify the starting and ending `cylinder`, `head`, and `sector` fields. They will be automatically computed using the BIOS geometry. If `-u` and `-s` are specified then the details of the specified partition will be changed. Any other partitions which overlap the requested part of the disk will be silently deleted.
`-F`	Indicate that `device` is a regular file. Unless the geometry of `device` is told to `fdisk` by `-T` `disktype`, `fdisk` will count the 512-byte sectors in `device` and produce a fake geometry.
`-i`	Explicitly request initialisation of the master boot code (similar to what `fdisk` `/mbr` does under MS-DOS), even if the magic number in the first sector is ok. The partition table is left alone by this (but see above).
`-l`	Lists known `sysid` values and exit.
`-r` `file`	Read the boot record from file `file` instead of the specified disk. The geometry information used is still that of the disk volume. Any changes are written back to the file.
`-s` `id/start/size`[`/bootmenu`]	Specify the partition `id`, `start`, `size`, and optionally `bootmenu`. Requires the use of a partition selection flag (`-0`, `-1`, `-2`, `-3`, or `-E` `number`)
`-S`	When used alone output `/bin/sh` commands for setting variables to the partition information. This could be used by installation scripts.
`-t disktab`	Read `disktype` from the named disktab(5) file instead of from `/etc/disktab`.
`-T` `disktype`	Use the `disktype` instead of the disklabel on `device`.
`-u`	Display the partitions and interactively ask which one to edit. `fdisk` will step through each field showing the old value and asking for a new one. The `start` and `size` can be specified in blocks (nn), cylinders (nnc), megabytes (nnm), or giga bytes (nng), values in megabytes and gigabytes will be rounded to the nearest cylinder boundary. The `size` may be specified as `$` in which case the partition will extend to the end of the available free space. `fdisk` will not create partitions which overlap. If `bootmenu` is specified for any partition `fdisk` will determine whether the installed boot code supports the bootselect code, if it doesn't you will be asked whether you want to install the required boot code.
`-v`	Be more verbose, specifying `-v` more than once may increase the amount of output. Using `-v` with `-u` allows the user to change more parameters than normally permitted.
`-w` `file`	Write the modified partition table to file `file` instead of the disk.

When called with no arguments, it outputs the partition table. An example

 Disk: /dev/rwd0d
         NetBSD disklabel disk geometry:
         cylinders: 16383, heads: 16, sectors/track: 63 (1008 sectors/cylinder)
         total sectors: 40032696

         BIOS disk geometry:
         cylinders: 1023, heads: 255, sectors/track: 63 (16065 sectors/cylinder)
         total sectors: 40032696

         Partition table:
         0: NetBSD (sysid 169)
             bootmenu: net 1.5.
             start 4209030, size 8289540 (4048 MB, Cyls 262-778), Active
         1: Primary DOS with 32 bit FAT (sysid 11)
             bootmenu: win98
             start 63, size 4208967 (2055 MB, Cyls 0-262)
         2: NetBSD (sysid 169)
             bootmenu: current
             start 32515560, size 7517136 (3670 MB, Cyls 2024-2491/234/40)
         3: Ext. partition - LBA (sysid 15)
             start 12498570, size 20016990 (9774 MB, Cyls 778-2024)
         Extended partition table:
         E0: NetBSD (sysid 169)
             bootmenu: test
             start 12498633, size 12305727 (6009 MB, Cyls 778-1544)
         E1: Primary DOS with 32 bit FAT (sysid 11)
             start 24804423, size 4096512 (2000 MB, Cyls 1544-1799)
         E2: Primary DOS with 32 bit FAT (sysid 11)
             start 28900998, size 3614562 (1765 MB, Cyls 1799-2024)
         Bootselector enabled, infinite timeout.

This example disk is divided into four partitions the last of which is an extended partition. The sub-partitions of the extended partition are also shown. In this case there is no free space in either the disk or in the extended partition.

The various fields in each partition entry are: ptn_number: id_name (sysid id_number) bootmenu: bootmenu start start, size size (MB MB, Cyls first-next) [, Active]

ptn_number is the number of the partition. id_name is the name of the filesystem type or operating system that uses this partition.

id_number is the number that identifies the partition type. 15 to an extended partition and 0 to mark a partition as unused. Use fdisk -l to list the known partition types.

bootmenu is the menu prompt output by the interactive boot code for this partition. This line is omitted if the prompt is not defined.

start, size are the start address and size of the partition in sectors.

MB is the size of the partition in megabytes.

first, next are the bounds of this partition displayed as cylinder/head/sector. If the partition starts (or ends) on a cylinder boundary the head and sector values are omitted. If -v is not specified the start of extended partitions and the first partition on the disk are rounded down to include the mandatory red tape in the preceding track.

Active is output if this is the active partition.

With -v two additional lines are output for each partition: beg: cylinder cylinder, head head, sector sector end: cylinder cylinder, head head, sector sector cylinder, head, sector are the beginning or ending address of a partition.

these numbers are read from the bootblock, so are the values calculated by a previous run of fdisk.

Specify -w file to write the output to a file and later specify -r file to read back .
This can be done without having write access to the disk volume.

See

parted, cfdisk, mkswap,