|
HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | DEVICES | SIZES | SCRIPT FILES | DISK LABELS | DOS MODE AND DOS 6.X WARNING | COLORS | ENVIRONMENT | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
|
|
|
FDISK(8) System Administration FDISK(8)
fdisk - manipulate disk partition table
fdisk [options] device
fdisk -l [device...]
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> advice 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.
-b, --sector-size sectorsize
Specify the sector size of the disk. Valid values are 512,
1024, 2048, and 4096. (Recent kernels know the sector size.
Use this option only on old kernels or to override the
kernel’s ideas.) Since util-linux-2.17, fdisk differentiates
between logical and physical sector size. This option changes
both sector sizes to sectorsize.
-B, --protect-boot
Don’t erase the beginning of the first disk sector when
creating a new disk label. This feature is supported for GPT
and MBR.
-c, --compatibility[=mode]
Specify the compatibility mode, 'dos' or 'nondos'. The
default is non-DOS mode. For backward compatibility, it is
possible to use the option without the mode argument — then
the default is used. Note that the optional mode argument
cannot be separated from the -c option by a space, the
correct form is for example -c=dos.
-h, --help
Display help text and exit.
-V, --version
Print version and exit.
-L, --color[=when]
Colorize the output. The optional argument when can be auto,
never or always. If the when argument is omitted, it defaults
to auto. The colors can be disabled; for the current built-in
default see the --help output. See also the COLORS section.
-l, --list
List the partition tables for the specified devices and then
exit.
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
Like --list, but provides more details.
--lock[=mode]
Use exclusive BSD lock for device or file it operates. The
optional argument mode can be yes, no (or 1 and 0) or
nonblock. If the mode argument is omitted, it defaults to
yes. This option overwrites environment variable
$LOCK_BLOCK_DEVICE. The default is not to use any lock at
all, but it’s recommended to avoid collisions with
systemd-udevd(8) or other tools.
-n, --noauto-pt
Don’t automatically create a default partition table on empty
device. The partition table has to be explicitly created by
user (by command like 'o', 'g', etc.).
-o, --output list
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, --getsz
Print the size in 512-byte sectors of each given block
device. This option is DEPRECATED in favour of blockdev(8).
-t, --type type
Enable support only for disklabels of the specified type, and
disable support for all other types.
-u, --units[=unit]
When listing partition tables, show sizes in 'sectors' or in
'cylinders'. The default is to show sizes in sectors. For
backward compatibility, it is possible to use the option
without the unit argument — then the default is used. Note
that the optional unit argument cannot be separated from the
-u option by a space, the correct form is for example
'-u=cylinders'.
-C, --cylinders number
Specify the number of cylinders of the disk. I have no idea
why anybody would want to do so.
-H, --heads number
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, --sectors number
Specify the number of sectors per track of the disk. (Not the
physical number, of course, but the number used for partition
tables.) A reasonable value is 63.
-w, --wipe when
Wipe filesystem, RAID and partition-table signatures from the
device, 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 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 also wipefs(8) command.
-W, --wipe-partitions when
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 signatures are wiped only when in interactive mode and
after confirmation by user. In all cases detected signatures
are reported by warning messages before a new partition is
created. See also wipefs(8) command.
-V, --version
Display version information and exit.
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).
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.
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).
GPT (GUID Partition Table)
GPT is modern standard for the layout of the partition table.
GPT uses 64-bit logical block addresses, checksums, UUIDs and
names for partitions and an unlimited number of partitions
(although the number of partitions is usually restricted to
128 in many partitioning tools).
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)
A DOS-type partition table can describe an unlimited number
of partitions. In sector 0 there is room for the description
of 4 partitions (called `primary'). One of these may be an
extended partition; this is a box holding logical partitions,
with descriptors found in a linked list of sectors, each
preceding the corresponding logical partitions. The four
primary partitions, 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
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
A BSD/Sun disklabel can describe 8 partitions, the third of
which should be a `whole disk' partition. Do not start a
partition that actually uses its first sector (like a swap
partition) at cylinder 0, since that will destroy the
disklabel. Note that a BSD label is usually nested within a
DOS partition.
IRIX/SGI-type
An IRIX/SGI disklabel can describe 16 partitions, the
eleventh of which should be an entire `volume' partition,
while the ninth should be labeled `volume header'. The volume
header will also cover the partition table, i.e., it starts
at block zero and 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 will lose the partition table. Use this type
of label only when working with Linux on IRIX/SGI machines or
IRIX/SGI disks under Linux.
A sync(2) and an ioctl(BLKRRPART) (rereading the partition
table from disk) are performed before exiting when the
partition table has been updated.
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.
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
The header of the output tables.
help-title
The help section titles.
warn
The warning messages.
welcome
The welcome message.
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.
LOCK_BLOCK_DEVICE=<mode>
use exclusive BSD lock. The mode is "1" or "0". See --lock
for more details.
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.
cfdisk(8), mkfs(8), partx(8), sfdisk(8)
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
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/>. This page
is part of the util-linux (a random collection of Linux
utilities) project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have
a bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-06-10.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in
this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
util-linux 2.41.devel-537-e... 2024-06-13 FDISK(8)
Pages that refer to this page: systemd-dissect(1), addpart(8), btrfs-filesystem(8), cfdisk(8), delpart(8), mkswap(8), parted(8), partx(8), resize2fs(8), resizepart(8), sfdisk(8)
|
HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|