Linux磁盘管理指令fdisk-man帮助手册

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
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 a help text 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 udevd 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.

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 than the number may be followed by the
multiplicative suffixes KiB=1024, MiB=1024*1024, 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, MB=1000*1000,
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)
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() 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 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
Implicit 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-title
The help section titles.

warn
The warning messages.

welcome
The welcome message.

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.

LOCK_BLOCK_DEVICE=<mode>
use exclusive BSD lock. The mode is "1" or "0". See --lock for more details.

AUTHORS
Karel Zak <[email protected]>, Davidlohr Bueso <[email protected]>

The original version was written by Andries E. Brouwer, A. V. Le Blanc and others.

SEE ALSO
cfdisk(8), mkfs(8), partx(8), sfdisk(8)

REPORTING BUGS
For bug reports, use the issue tracker at
https://github.com/karelzak/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/>.

util-linux 2.37.4 2022-02-14 FDISK(8)