fdisk
fdisk
It seems like you're interested in learning about fdisk, a command-line utility used for disk partitioning in Unix-like operating systems. fdisk is a powerful tool that allows users to create, delete, modify, and manage disk partitions on hard drives. Here's an overview of fdisk and its common usage:
Overview of fdisk
fdiskPurpose: fdisk is used to perform various disk partitioning tasks, such as creating, deleting, and resizing partitions on hard drives.
Availability: fdisk is typically included with most Unix-like operating systems, including Linux distributions.
Common fdisk Commands and Usage
fdisk Commands and UsageDisplay Partition Table:
To view the current partition table of a disk:
fdisk -l /dev/sdaReplace
/dev/sdawith the disk device you want to inspect.
Creating a New Partition:
To create a new partition:
fdisk /dev/sdaType
nto create a new partition.Specify the partition type, start sector, and end sector.
Write changes to disk using
w.
Deleting a Partition:
To delete an existing partition:
fdisk /dev/sdaType
dto delete a partition.Select the partition number to delete.
Write changes to disk using
w.
Changing Partition Type:
To change the type of an existing partition:
fdisk /dev/sdaType
tto change a partition's system ID (type).Select the partition number and enter the new hexadecimal code for the partition type.
Write changes to disk using
w.
Printing Help and Options:
To print a summary of
fdiskcommands and options:fdisk --help
Considerations
Data Loss: Be cautious when using
fdiskas it directly manipulates partition tables, and incorrect operations can result in data loss.Backup: Always back up important data before making any changes to disk partitions.
Alternatives
GNU Parted (
parted): Provides a more user-friendly interface with additional features like resizing partitions while they are in use.GParted: A graphical front-end for
partedthat offers a visual representation of disk partitions and makes it easier to manage partitioning tasks.
Conclusion
fdisk is a fundamental tool for disk partitioning on Unix-like systems, offering powerful capabilities to manage disk partitions directly from the command line. It's essential to understand its commands and use them carefully to avoid unintended data loss or system issues.
help
Usage:
fdisk [options] <disk> change partition table
fdisk [options] -l [<disk>...] list partition table(s)
Display or manipulate a disk partition table.
Options:
-b, --sector-size <size> physical and logical sector size
-B, --protect-boot don't erase bootbits when creating a new label
-c, --compatibility[=<mode>] mode is 'dos' or 'nondos' (default)
-L, --color[=<when>] colorize output (auto, always or never)
colors are enabled by default
-l, --list display partitions and exit
-x, --list-details like --list but with more details
-n, --noauto-pt don't create default partition table on empty devices
-o, --output <list> output columns
-t, --type <type> recognize specified partition table type only
-u, --units[=<unit>] display units: 'cylinders' or 'sectors' (default)
-s, --getsz display device size in 512-byte sectors [DEPRECATED]
--bytes print SIZE in bytes rather than in human readable format
--lock[=<mode>] use exclusive device lock (yes, no or nonblock)
-w, --wipe <mode> wipe signatures (auto, always or never)
-W, --wipe-partitions <mode> wipe signatures from new partitions (auto, always or never)
-C, --cylinders <number> specify the number of cylinders
-H, --heads <number> specify the number of heads
-S, --sectors <number> specify the number of sectors per track
-h, --help display this help
-V, --version display version
Available output columns:
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
man
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 help text and exit.
-V, --version
-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
-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(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
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
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.
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