| FDISK(8) | System Administration | FDISK(8) |
NAME¶
fdisk - manipulate disk partition table
SYNOPSIS¶
fdisk [options] device
fdisk -l [device...]
DESCRIPTION¶
fdisk is a dialog-driven program for creation and manipulation of partition tables. It understands GPT, MBR, Sun, SGI and BSD partition tables.
Block devices can be divided into one or more logical disks called partitions. This division is recorded in the partition table, usually found in sector 0 of the disk. (In the BSD world one talks about `disk slices' and a `disklabel'.)
All partitioning is driven by device I/O limits (the topology) by default. fdisk is able to optimize the disk layout for a 4K-sector size and use an alignment offset on modern devices for MBR and GPT. It is always a good idea to follow fdisk's defaults as the default values (e.g., first and last partition sectors) and partition sizes specified by the +/-<size>{M,G,...} notation are always aligned according to the device properties.
CHS (Cylinder-Head-Sector) addressing is deprecated and not used by default. Please, do not follow old articles and recommendations with fdisk -S <n> -H <n> advices for SSD or 4K-sector devices.
Note that partx(8) provides a rich interface for scripts to print disk layouts, fdisk is mostly designed for humans. Backward compatibility in the output of fdisk is not guaranteed. The input (the commands) should always be backward compatible.
OPTIONS¶
-b, --sector-size sectorsize
-B, --protect-boot
-c, --compatibility[=mode]
-h, --help
-V, --version
-L, --color[=when]
-l, --list
If no devices are given, the devices mentioned in /proc/partitions (if this file exists) are used. Devices are always listed in the order in which they are specified on the command-line, or by the kernel listed in /proc/partitions.
-x, --list-details
--lock[=mode]
-n, --noauto-pt
-o, --output list
The default list of columns may be extended if list is specified in the format +list (e.g., -o +UUID).
-s, --getsz
-t, --type type
-u, --units[=unit]
-C, --cylinders number
-H, --heads number
-S, --sectors number
-w, --wipe when
-W, --wipe-partitions when
-V, --version
DEVICES¶
The device is usually /dev/sda, /dev/sdb or so. A device name refers to the entire disk. Old systems without libata (a library used inside the Linux kernel to support ATA host controllers and devices) make a difference between IDE and SCSI disks. In such cases the device 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 disk in the system. See also Linux kernel documentation (the Documentation/admin-guide/devices.txt file).
SIZES¶
The "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. If the size is prefixed by '-' then it is interpreted as relative to the high limit (last available sector for the partition).
In the case the size is specified in bytes, then the number may be followed by the multiplicative suffixes KiB (1024 bytes), MiB (1024*1024 bytes), and so on for GiB, TiB, PiB, EiB, ZiB and 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 bytes), MB (1000*1000 bytes), and so on for GB, TB, PB, EB, ZB and YB. These 10^N suffixes are deprecated.
SCRIPT FILES¶
fdisk allows reading (by 'I' command) sfdisk(8) compatible script files. The script is applied to in-memory partition table, and then it is 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(8), sfdisk(8), fdisk and other libfdisk applications. For more details see sfdisk(8).
DISK LABELS¶
GPT (GUID Partition Table)
Note that the first sector is still reserved for a protective MBR in the GPT specification. It prevents MBR-only partitioning tools 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)
In a DOS-type partition table the starting offset and the size of each partition is stored in two ways: as an absolute number of sectors (given in 32 bits), and as a Cylinders/Heads/Sectors triple (given in 10+8+6 bits). The former is OK — with 512-byte sectors this will work up to 2 TB. The latter has two problems. First, these C/H/S fields can be filled only when the 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/S addressing 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 by default.
BSD/Sun-type
IRIX/SGI-type
A sync(2) and an ioctl(BLKRRPART) (rereading the partition table from disk) are performed before exiting when the partition table has been updated.
DOS MODE AND DOS 6.X WARNING¶
Note that all this is deprecated. You don’t have to care about things like geometry and cylinders on modern operating systems. If you really want DOS-compatible partitioning then you have to enable DOS mode and cylinder units by using the '-c=dos -u=cylinders' fdisk command-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 information as more reliable than the information in the partition table. DOS FORMAT expects DOS FDISK to clear the first 512 bytes of the data area of a partition whenever a size change occurs. DOS FORMAT will look at this extra information even if the /U flag is given — we consider this a bug in DOS FORMAT and DOS FDISK.
The bottom line is that if you use fdisk or cfdisk(8) to change the size of a DOS partition table entry, then you must also use dd(1) to zero the first 512 bytes of that partition before using DOS FORMAT to format the partition. For example, if you were using fdisk to make a DOS partition table entry for /dev/sda1, then (after exiting fdisk and rebooting Linux so that the partition table information is 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 do not really have anything like a physical geometry, certainly not something that can be described in the simplistic Cylinders/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 be shared with other operating systems, it is often a good idea to let an fdisk from another operating system make at least one partition. When Linux boots it looks at the partition table, and tries to deduce what (fake) geometry is required for good cooperation with other systems.
Whenever a partition table is printed out in DOS mode, a consistency check is performed on the partition table entries. This check verifies that the physical and logical start and end points are identical, and that each partition starts and ends on a cylinder boundary (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/2 on your machine.
For best results, you should always use an OS-specific partition table program. For example, you should make DOS partitions with the DOS FDISK program and Linux partitions with the Linux fdisk or Linux cfdisk(8) programs.
COLORS¶
The output colorization is implemented by terminal-colors.d(5) functionality. Implicit coloring can be disabled by an empty file
/etc/terminal-colors.d/fdisk.disable
for the fdisk command or for all tools by
/etc/terminal-colors.d/disable
The user-specific $XDG_CONFIG_HOME/terminal-colors.d or $HOME/.config/terminal-colors.d overrides the global setting.
Note that the output colorization may be enabled by default, and in this case terminal-colors.d directories do not have to exist yet.
The logical color names supported by fdisk are:
header
help-title
warn
welcome
ENVIRONMENT¶
FDISK_DEBUG=all
LIBFDISK_DEBUG=all
LIBBLKID_DEBUG=all
LIBSMARTCOLS_DEBUG=all
LIBSMARTCOLS_DEBUG_PADDING=on
LOCK_BLOCK_DEVICE=<mode>
AUTHORS¶
Karel Zak <kzak@redhat.com>, Davidlohr Bueso <dave@gnu.org>
The original version was written by Andries E. Brouwer, A. V. Le Blanc and others.
SEE ALSO¶
REPORTING BUGS¶
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.
AVAILABILITY¶
The fdisk command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.
| 2024-07-04 | util-linux 2.40.2 |