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`

Purpose: 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

Display Partition Table:
- To view the current partition table of a disk:
  fdisk -l /dev/sda
  Replace /dev/sda with the disk device you want to inspect.
Creating a New Partition:
- To create a new partition:
  fdisk /dev/sda
  - Type n to 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/sda
  - Type d to 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/sda
  - Type t to 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 fdisk commands and options:
  fdisk --help

Considerations

Data Loss: Be cautious when using fdisk as 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 parted that 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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Last updated 1 year ago

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

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.