-b

Specify the sector size of the disk. Valid values are 512, 1024, 2048, and 4096. (Recent kernels know the sector size. Usethis option only on old kernels or to override the kernel's ideas.) Since util-linux-2.17, fdisk differentiates between logi‐cal and physical sector size. This option changes both sector sizes to sectorsize.

-B

Don't erase the begin of the first disk sector when create a new disk label. This feature is supported for GPT and MBR.

-c

Specify the compatibility mode, 'dos' or 'nondos'. The default is non-DOS mode. For backward compatibility, it is possibleto use the option without the mode argument -- then the default is used. Note that the optional mode argument cannot be sepa‐rated from the -c option by a space, the correct form is for example '-c=dos'.

-h

Display a help text and exit.

-L

Colorize the output. The optional argument when can be auto, never or always. If the when argument is omitted, it defaultsto auto. The colors can be disabled; for the current built-in default see the --help output. See also the COLORS section.

-l

List the partition tables for the specified devices and then exit. If no devices are given, those mentioned in /proc/parti‐tions (if that file exists) are used.

-o

Specify which output columns to print. Use --help to get a list of all supported columns.The default list of columns may be extended if list is specified in the format +list (e.g. -o +UUID).

-s

Print the size in 512-byte sectors of each given block device. This option is DEPRECATED in favour of blockdev(1).

-t

Enable support only for disklabels of the specified type, and disable support for all other types.

-u

When listing partition tables, show sizes in 'sectors' or in 'cylinders'. The default is to show sizes in sectors. For back‐ward compatibility, it is possible to use the option without the unit argument -- then the default is used. Note that theoptional unit argument cannot be separated from the -u option by a space, the correct form is for example '-u=cylinders'.

-C

Specify the number of cylinders of the disk. I have no idea why anybody would want to do so.

-H

Specify the number of heads of the disk. (Not the physical number, of course, but the number used for partition tables.)Reasonable values are 255 and 16.

-S

Specify the number of sectors per track of the disk. (Not the physical number, of course, but the number used for partitiontables.) A reasonable value is 63.

-w

Wipe filesystem, RAID and partition-table signatures from the device, in order to avoid possible collisions. The argumentwhen can be auto, never or always. When this option is not given, the default is auto, in which case signatures are wipedonly when in interactive mode. In all cases detected signatures are reported by warning messages before a new partition tableis created. See also wipefs(8) command.

-W

Wipe filesystem, RAID and partition-table signatures from a newly created partitions, in order to avoid possible collisions.The argument when can be auto, never or always. When this option is not given, the default is auto, in which case signaturesare wiped only when in interactive mode and after confirmation by user. In all cases detected signatures are reported bywarning messages before a new partition is created. See also wipefs(8) command.

-V

Display version information and exit.DEVICESThe device is usually /dev/sda, /dev/sdb or so. A device name refers to the entire disk. Old systems without libata (a library usedinside the Linux kernel to support ATA host controllers and devices) make a difference between IDE and SCSI disks. In such cases thedevice name will be /dev/hd* (IDE) or /dev/sd* (SCSI).The partition is a device name followed by a partition number. For example, /dev/sda1 is the first partition on the first hard diskin the system. See also Linux kernel documentation (the Documentation/devices.txt file).SIZESThe "last sector" dialog accepts partition size specified by number of sectors or by +<size>{K,B,M,G,...} notation.If the size is prefixed by '+' then it is interpreted as relative to the partition first sector. In this case the size is expectedin bytes and the number may be followed by the multiplicative suffixes KiB=1024, MiB=1024*1024, and so on for GiB, TiB, PiB, EiB, ZiBand YiB. The "iB" is optional, e.g. "K" has the same meaning as "KiB".The relative sizes are always aligned according to device I/O limits. The +<size>{K,B,M,G,...} notation is recommended.For backward compatibility fdisk also accepts the suffixes KB=1000, MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB. These 10^Nsuffixes are deprecated.SCRIPT FILESfdisk allows to read (by 'I' command) sfdisk compatible script files. The script is applied to in-memory partition table, and then itis possible to modify the partition table before you write it to the device.And vice-versa it is possible to write the current in-memory disk layout to the script file by command 'O'.The script files are compatible between cfdisk, sfdisk, fdisk and another libfdisk applications. For more details see sfdisk(8).DISK LABELSGPT (GUID Partition Table)GPT is modern standard for the layout of the partition table. GPT uses 64-bit logical block addresses, checksums, UUIDs andnames for partitions and an unlimited number of partitions (although the number of partitions is usually restricted to 128 inmany partitioning tools).Note that the first sector is still reserved for a protective MBR in the GPT specification. It prevents MBR-only partitioningtools from mis-recognizing and overwriting GPT disks.GPT is always a better choice than MBR, especially on modern hardware with a UEFI boot loader.DOS-type (MBR)A DOS-type partition table can describe an unlimited number of partitions. In sector 0 there is room for the description of 4partitions (called `primary'). One of these may be an extended partition; this is a box holding logical partitions, withdescriptors found in a linked list of sectors, each preceding the corresponding logical partitions. The four primary parti‐tions, present or not, get numbers 1-4. Logical partitions are numbered starting from 5.In a DOS-type partition table the starting offset and the size of each partition is stored in two ways: as an absolute numberof sectors (given in 32 bits), and as a Cylinders/Heads/Sectors triple (given in 10+8+6 bits). The former is OK -- with512-byte sectors this will work up to 2 TB. The latter has two problems. First, these C/H/S fields can be filled only whenthe number of heads and the number of sectors per track are known. And second, even if we know what these numbers should be,the 24 bits that are available do not suffice. DOS uses C/H/S only, Windows uses both, Linux never uses C/H/S. The C/H/Saddressing is deprecated and may be unsupported in some later fdisk version.Please, read the DOS-mode section if you want DOS-compatible partitions. fdisk does not care about cylinder boundaries bydefault.BSD/Sun-typeA BSD/Sun disklabel can describe 8 partitions, the third of which should be a `whole disk' partition. Do not start a parti‐tion that actually uses its first sector (like a swap partition) at cylinder 0, since that will destroy the disklabel. Notethat a BSD label is usually nested within a DOS partition.IRIX/SGI-typeAn IRIX/SGI disklabel can describe 16 partitions, the eleventh of which should be an entire `volume' partition, while theninth should be labeled `volume header'. The volume header will also cover the partition table, i.e., it starts at block zeroand extends by default over five cylinders. The remaining space in the volume header may be used by header directory entries.No partitions may overlap with the volume header. Also do not change its type or make some filesystem on it, since you willlose the partition table. Use this type of label only when working with Linux on IRIX/SGI machines or IRIX/SGI disks underLinux.A sync() and an ioctl(BLKRRPART) (rereading the partition table from disk) are performed before exiting when the partition table hasbeen updated.DOS mode and DOS 6.x WARNINGNote that all this is deprecated. You don't have to care about things like geometry and cylinders on modern operating systems. If youreally want DOS-compatible partitioning then you have to enable DOS mode and cylinder units by using the '-c=dos -u=cylinders' fdiskcommand-line options.The DOS 6.x FORMAT command looks for some information in the first sector of the data area of the partition, and treats this informa‐tion as more reliable than the information in the partition table. DOS FORMAT expects DOS FDISK to clear the first 512 bytes of thedata area of a partition whenever a size change occurs. DOS FORMAT will look at this extra information even if the /U flag is given

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The bottom line is that if you use fdisk or cfdisk to change the size of a DOS partition table entry, then you must also use dd(1) tozero the first 512 bytes of that partition before using DOS FORMAT to format the partition. For example, if you were using fdisk tomake a DOS partition table entry for /dev/sda1, then (after exiting fdisk and rebooting Linux so that the partition table informationis valid) you would use the command "dd if=/dev/zero of=/dev/sda1 bs=512 count=1" to zero the first 512 bytes of the partition.fdisk usually obtains the disk geometry automatically. This is not necessarily the physical disk geometry (indeed, modern disks donot really have anything like a physical geometry, certainly not something that can be described in the simplistic Cylin‐ders/Heads/Sectors form), but it is the disk geometry that MS-DOS uses for the partition table.Usually all goes well by default, and there are no problems if Linux is the only system on the disk. However, if the disk has to beshared with other operating systems, it is often a good idea to let an fdisk from another operating system make at least one parti‐tion. When Linux boots it looks at the partition table, and tries to deduce what (fake) geometry is required for good cooperationwith other systems.Whenever a partition table is printed out in DOS mode, a consistency check is performed on the partition table entries. This checkverifies that the physical and logical start and end points are identical, and that each partition starts and ends on a cylinderboundary (except for the first partition).Some versions of MS-DOS create a first partition which does not begin on a cylinder boundary, but on sector 2 of the first cylinder.Partitions beginning in cylinder 1 cannot begin on a cylinder boundary, but this is unlikely to cause difficulty unless you have OS/2on your machine.For best results, you should always use an OS-specific partition table program. For example, you should make DOS partitions with theDOS FDISK program and Linux partitions with the Linux fdisk or Linux cfdisk programs.COLORSImplicit coloring can be disabled by an empty file /etc/terminal-colors.d/fdisk.disable.See terminal-colors.d(5) for more details about colorization configuration. The logical color names supported by fdisk are:header The header of the output tables.help-titleThe help section titles.warn The warning messages.welcomeThe welcome message.AUTHORSKarel Zak ⟨kzak@redhat.com⟩Davidlohr Bueso ⟨dave@gnu.org⟩The original version was written by Andries E. Brouwer, A. V. Le Blanc and others.ENVIRONMENTFDISK_DEBUG=allenables fdisk debug output.LIBFDISK_DEBUG=allenables libfdisk debug output.LIBBLKID_DEBUG=allenables libblkid debug output.LIBSMARTCOLS_DEBUG=allenables libsmartcols debug output.LIBSMARTCOLS_DEBUG_PADDING=onuse visible padding characters. Requires enabled LIBSMARTCOLS_DEBUG.