Ubuntu Manpage: sfdisk - display or manipulate a disk partition table

Provided by: fdisk_2.40.2-1ubuntu1.1_amd64

NAME

       sfdisk - display or manipulate a disk partition table

SYNOPSIS

       sfdisk [options] device [-N partition-number]

       sfdisk [options] command

DESCRIPTION

sfdisk is a script-oriented tool for partitioning any block device. It runs in interactive mode if
executed on a terminal (stdin refers to a terminal).

Since version 2.26 sfdisk supports MBR (DOS), GPT, SUN and SGI disk labels, but no longer provides any
functionality for CHS (Cylinder-Head-Sector) addressing. CHS has never been important for Linux, and this
addressing concept does not make any sense for new devices.

sfdisk protects the first disk sector when create a new disk label. The option --wipe always disables
this protection. Note that fdisk(8) and cfdisk(8) completely erase this area by default.

sfdisk (since version 2.26) aligns the start and end of partitions to block-device I/O limits when
relative sizes are specified, when the default values are used or when multiplicative suffixes (e.g.,
MiB) are used for sizes. It is possible that partition size will be optimized (reduced or enlarged) due
to alignment if the start offset is specified exactly in sectors and partition size relative or by
multiplicative suffixes.

The recommended way is not to specify start offsets at all and specify partition size in MiB, GiB (or
so). In this case sfdisk aligns all partitions to block-device I/O limits (or when I/O limits are too
small then to megabyte boundary to keep disk layout portable). If this default behaviour is unwanted
(usually for very small partitions) then specify offsets and sizes in sectors. In this case sfdisk
entirely follows specified numbers without any optimization.

sfdisk does not create the standard system partitions for SGI and SUN disk labels like fdisk(8) does. It
is necessary to explicitly create all partitions including whole-disk system partitions.

sfdisk uses BLKRRPART (reread partition table) ioctl to make sure that the device is not used by system
or other tools (see also --no-reread). It’s possible that this feature or another sfdisk activity races
with systemd-udevd(8). The recommended way how to avoid possible collisions is to use --lock option. The
exclusive lock will cause systemd-udevd to skip the event handling on the device.

The sfdisk prompt is only a hint for users and a displayed partition number does not mean that the same
partition table entry will be created (if -N not specified), especially for tables with gaps.

COMMANDS

The commands are mutually exclusive.

[-N partition-number] device
The default sfdisk command is to read the specification for the desired partitioning of device from
standard input, and then create a partition table according to the specification. See below for the
description of the input format. If standard input is a terminal, then sfdisk starts an interactive
session.

If the option -N is specified, then the changes are applied to the partition addressed by
partition-number. The unspecified fields of the partition are not modified.

Note that it’s possible to address an unused partition with -N. For example, an MBR always contains 4
partitions, but the number of used partitions may be smaller. In this case sfdisk follows the default
values from the partition table and does not use built-in defaults for the unused partition given
with -N. See also --append.

-A, --activate device [partition-number...]
Switch on the bootable flag for the specified partitions and switch off the bootable flag on all
unspecified partitions. The special placeholder '-' may be used instead of the partition numbers to
switch off the bootable flag on all partitions.

The activation command is supported for MBR and PMBR only. If a GPT label is detected, then sfdisk
prints warning and automatically enters PMBR.

If no partition-number is specified, then list the partitions with an enabled flag.

--backup-pt-sectors device
Back up the current partition table sectors in binary format and exit. See the BACKING UP THE
PARTITION TABLE section.

--delete device [partition-number...]
Delete all or the specified partitions.

-d, --dump device
Dump the partitions of a device in a format that is usable as input to sfdisk. See the BACKING UP THE
PARTITION TABLE section.

-g, --show-geometry [device...]
List the geometry of all or the specified devices. For backward compatibility the deprecated option
--show-pt-geometry have the same meaning as this one.

-J, --json device
Dump the partitions of a device in JSON format. Note that sfdisk is not able to use JSON as input
format.

-l, --list [device...]
List the partitions of all or the specified devices. This command can be used together with --verify.

-F, --list-free [device...]
List the free unpartitioned areas on all or the specified devices.

--part-attrs device partition-number [attributes]
Change the GPT partition attribute bits. If attributes is not specified, then print the current
partition settings. The attributes argument is a comma- or space-delimited list of bits numbers or
bit names. For example, the string "RequiredPartition,50,51" sets three bits. The currently supported
attribute bits are:

Bit 0 (RequiredPartition)
If this bit is set, the partition is required for the platform to function. The creator of the
partition indicates that deletion or modification of the contents can result in loss of platform
features or failure for the platform to boot or operate. The system cannot function normally if
this partition is removed, and it should be considered part of the hardware of the system.

Bit 1 (NoBlockIOProtocol)
EFI firmware should ignore the content of the partition and not try to read from it.

Bit 2 (LegacyBIOSBootable)
The partition may be bootable by legacy BIOS firmware.

Bits 3-47
Undefined and must be zero. Reserved for expansion by future versions of the UEFI specification.

Bits 48-63
Reserved for GUID specific use. The use of these bits will vary depending on the partition type.
For example Microsoft uses bit 60 to indicate read-only, 61 for shadow copy of another partition,
62 for hidden partitions and 63 to disable automount.

--part-label device partition-number [label]
Change the GPT partition name (label). If label is not specified, then print the current partition
label.

--part-type device partition-number [type]
Change the partition type. If type is not specified, then print the current partition type.

The type argument is hexadecimal for MBR, GUID for GPT, type alias (e.g. "linux") or type shortcut
(e.g. 'L'). For backward compatibility the options -c and --id have the same meaning as this one.

--part-uuid device partition-number [uuid]
Change the GPT partition UUID. If uuid is not specified, then print the current partition UUID.

--disk-id device [id]
Change the disk identifier. If id is not specified, then print the current identifier. The identifier
is UUID for GPT or unsigned integer for MBR.

-r, --reorder device
Renumber the partitions, ordering them by their start offset.

-s, --show-size [device...]
List the sizes of all or the specified devices in units of 1024 byte size. This command is DEPRECATED
in favour of blockdev(8).

-T, --list-types
Print all supported types for the current disk label or the label specified by --label.

-V, --verify [device...]
Test whether the partition table and partitions seem correct.

--relocate oper device
Relocate partition table header. This command is currently supported for GPT header only. The
argument oper can be:

gpt-bak-std
Move GPT backup header to the standard location at the end of the device.

gpt-bak-mini
Move GPT backup header behind the last partition. Note that UEFI standard requires the backup
header at the end of the device and partitioning tools can automatically relocate the header to
follow the standard.

OPTIONS

-a, --append
Don’t create a new partition table, but only append the specified partitions.

Note that unused partition maybe be re-used in this case although it is not the last partition in the
partition table. See also -N to specify entry in the partition table.

-b, --backup
Back up the current partition table sectors before starting the partitioning. The default backup file
name is ~/sfdisk-<device>-<offset>.bak; to use another name see option -O, --backup-file. See section
BACKING UP THE PARTITION TABLE for more details.

--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.

-f, --force
Disable all consistency checking.

--Linux
Deprecated and ignored option. Partitioning that is compatible with Linux (and other modern operating
systems) is the default.

--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, --no-act
Do everything except writing to the device.

--no-reread
Do not check through the re-read-partition-table ioctl whether the device is in use.

--no-tell-kernel
Don’t tell the kernel about partition changes. This option is recommended together with --no-reread
to modify a partition on used disk. The modified partition should not be used (e.g., mounted).

-O, --backup-file path
Override the default backup file name. Note that the device name and offset are always appended to
the file name.

--move-data[=path]
Move data after partition relocation, for example when moving the beginning of a partition to another
place on the disk. The size of the partition has to remain the same, the new and old location may
overlap. This option requires option -N in order to be processed on one specific partition only.

The optional path specifies log file name. The log file contains information about all read/write
operations on the partition data. The word "@default" as a path forces sfdisk to use
~/sfdisk-<devname>.move for the log. The log is optional since v2.35.

Note that this operation is risky and not atomic. Don’t forget to backup your data!

INPUT FORMATS

sfdisk supports two input formats and generic header lines.

Header lines
The optional header lines specify generic information that apply to the partition table. The header-line
format is:

The currently recognized headers are:

unit
Specify the partitioning unit. The only supported unit is sectors.

label
Specify the partition table type. For example dos or gpt.

label-id
Specify the partition table identifier. It should be a hexadecimal number (with a 0x prefix) for MBR
and a UUID for GPT.

first-lba
Specify the first usable sector for GPT partitions. This header is ignored if the script and device
sector size differ. In this case sfdisk uses label specific default.

last-lba
Specify the last usable sector for GPT partitions. This header is ignored if the script and device
sector size differ. In this case sfdisk uses label specific default.

table-length
Specify the maximal number of GPT partitions.

grain
Specify minimal size in bytes used to calculate partitions alignment. The default is 1MiB and it’s
strongly recommended to use the default. Do not modify this variable if you’re not sure.

sector-size
Specify sector size. sfdisk always uses device sector size. Since version 2.39 sfdisk recalculates
sizes from dump if the script and device sector size differ.

Note that it is only possible to use header lines before the first partition is specified in the input.

Unnamed-fields format
start size type bootable

where each line fills one partition descriptor.

Fields are separated by whitespace, comma (recommended) or semicolon possibly followed by whitespace;
initial and trailing whitespace is ignored. Numbers can be octal, decimal or hexadecimal; decimal is the
default. When a field is absent, empty or specified as '-' a default value is used. But when the -N
option (change a single partition) is given, the default for each field is its previous value.

The default value of start is the first non-assigned sector aligned according to device I/O limits. The
default start offset for the first partition is 1 MiB. If the offset is followed by the multiplicative
suffixes (KiB, MiB, GiB, TiB, PiB, EiB, ZiB and YiB), then the number is interpreted as offset in bytes.
Since v2.38 when the -N option (change a single partition) is given, a '+' can be used to enlarge
partition by move start of the partition if there is a free space before the partition.

The default value of size indicates "as much as possible"; i.e., until the next partition or
end-of-device. A numerical argument is by default interpreted as a number of sectors, however if the size
is followed by one of the multiplicative suffixes (KiB, MiB, GiB, TiB, PiB, EiB, ZiB and YiB) then the
number is interpreted as the size of the partition in bytes and it is then aligned according to the
device I/O limits. A '+' can be used instead of a number to enlarge the partition as much as possible.
Note '+' is equivalent to the default behaviour for a new partition; existing partitions will be resized
as required.

The partition type is given in hex for MBR (DOS) where 0x prefix is optional; a GUID string for GPT; a
shortcut or an alias. It’s recommended to use two letters for MBR hex codes to avoid collision between
deprecated shortcut 'E' and '0E' MBR hex code. For backward compatibility sfdisk tries to interpret type
as a shortcut as a first possibility in partitioning scripts although on other places (e.g. --part-type
command) it tries shortcuts as the last possibility.

Since v2.36 libfdisk supports partition type aliases as extension to shortcuts. The alias is a simple
human readable word (e.g. "linux").

Since v2.37 libfdisk supports partition type names on input, ignoring the case of the characters and all
non-alphanumeric and non-digit characters in the name (e.g. "Linux /usr x86" is the same as "linux
usr-x86").

Supported shortcuts and aliases:

L - alias 'linux'
Linux; means 83 for MBR and 0FC63DAF-8483-4772-8E79-3D69D8477DE4 for GPT.

S - alias 'swap'
swap area; means 82 for MBR and 0657FD6D-A4AB-43C4-84E5-0933C84B4F4F for GPT

Ex - alias 'extended'
MBR extended partition; means 05 for MBR. The original shortcut 'E' is deprecated due to collision
with 0x0E MBR partition type.

H - alias 'home'
home partition; means 933AC7E1-2EB4-4F13-B844-0E14E2AEF915 for GPT

U - alias 'uefi'
EFI System partition, means EF for MBR and C12A7328-F81F-11D2-BA4B-00A0C93EC93B for GPT

R - alias 'raid'
Linux RAID; means FD for MBR and A19D880F-05FC-4D3B-A006-743F0F84911E for GPT

V - alias 'lvm'
LVM; means 8E for MBR and E6D6D379-F507-44C2-A23C-238F2A3DF928 for GPT

The default type value is linux.

The shortcut 'X' for Linux extended partition (85) is deprecated in favour of 'Ex'.

bootable is specified as [*|-], with as default not-bootable. The value of this field is irrelevant for
Linux - when Linux runs it has been booted already - but it might play a role for certain boot loaders
and for other operating systems.

Named-fields format
This format is more readable, robust, extensible and allows specifying additional information (e.g., a
UUID). It is recommended to use this format to keep your scripts more readable.

[device :] name[=value], ...

The device field is optional. sfdisk extracts the partition number from the device name. It allows
specifying the partitions in random order. This functionality is mostly used by --dump. Don’t use it if
you are not sure.

The value can be between quotation marks (e.g., name="This is partition name"). The fields start= and
size= support '+' and '-' in the same way as Unnamed-fields format.

The currently supported fields are:

start=number
The first non-assigned sector aligned according to device I/O limits. The default start offset for
the first partition is 1 MiB. If the offset is followed by the multiplicative suffixes (KiB, MiB,
GiB, TiB, PiB, EiB, ZiB and YiB), then the number is interpreted as offset in bytes.

size=number
Specify the partition size in sectors. The number may be followed by the multiplicative suffixes
(KiB, MiB, GiB, TiB, PiB, EiB, ZiB and YiB), then it’s interpreted as size in bytes and the size is
aligned according to device I/O limits.

bootable
Mark the partition as bootable.

attrs=string
Partition attributes, usually GPT partition attribute bits. See --part-attrs for more details about
the GPT-bits string format.

uuid=string
GPT partition UUID.

name=string
GPT partition name.

type=code
A hexadecimal number (without 0x) for an MBR partition, a GUID for a GPT partition, a shortcut as for
unnamed-fields format or a type name (e.g. type="Linux /usr (x86)"). See above the section about the
unnamed-fields format for more details. For backward compatibility the Id= field has the same
meaning.

EMPTY DISK LABEL

       sfdisk does not create partition table without partitions by default. The lines with partitions are
       expected in the script by default. The empty partition table has to be explicitly requested by "label:
       <name>" script header line without any partitions lines. For example:

          echo 'label: gpt' | sfdisk /dev/sdb

       creates empty GPT partition table. Note that the --append disables this feature.

BACKING UP THE PARTITION TABLE

It is recommended to save the layout of your devices. sfdisk supports two ways.

Dump in sfdisk compatible format
Use the --dump command to save a description of the device layout to a text file. The dump format is
suitable for later sfdisk input. For example:

sfdisk --dump /dev/sda > sda.dump

This can later be restored by:

sfdisk /dev/sda < sda.dump

Note that sfdisk completely restores partition types and partition UUIDs. This could potentially become
problematic if you duplicate the same layout to different disks, as it may result in duplicate UUIDs
within your system.

Full binary backup
If you want to do a full binary backup of all sectors where the partition table is stored, then use the
--backup-pt-sectors command. It writes the sectors to ~/sfdisk-<device>-<offset>.bak files. The default
name of the backup file can be changed with the --backup-file option. The backup files contain only raw
data from the device. For example:

sfdisk --backup-pt-sectors /dev/sda

The GPT header can later be restored by:

dd if=~/sfdisk-sda-0x00000200.bak of=/dev/sda seek=$((0x00000200)) bs=1 conv=notrunc

It’s also possible to use the --backup option to create the same backup immediately after startup for
other sfdisk commands. For example, backup partition table before deleting all partitions from partition
table:

sfdisk --backup --delete /dev/sda

The same concept of backup files is used by wipefs(8).

Note that sfdisk since version 2.26 no longer provides the -I option to restore sectors. dd(1) provides
all necessary functionality.

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/sfdisk.disable

       for the sfdisk 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 sfdisk are:

       header
           The header of the output tables.

       warn
           The warning messages.

       welcome
           The welcome message.

ENVIRONMENT

       SFDISK_DEBUG=all
           enables sfdisk debug output.

       LIBFDISK_DEBUG=all
           enables libfdisk debug output.

       LIBBLKID_DEBUG=all
           enables libblkid debug output.

       LIBSMARTCOLS_DEBUG=all
           enables libsmartcols debug output.

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

NOTES

       Since version 2.26 sfdisk no longer provides the -R or --re-read option to force the kernel to reread the
       partition table. Use blockdev --rereadpt instead.

       Since version 2.26 sfdisk does not provide the --DOS, --IBM, --DOS-extended, --unhide, --show-extended,
       --cylinders, --heads, --sectors, --inside-outer, --not-inside-outer options.

EXAMPLES

       sfdisk --list --label-nested=mbr /dev/sda
           Print protective MBR on device with GPT disk label.

       echo -e ',10M,L\n,10M,L\n,+,\n' | sfdisk /dev/sdc
           Create three Linux partitions, with the default start, the size of the first two partitions is 10MiB,
           and the last partition fills all available space on the device.

       echo -e 'size=10M, type=L\n size=10M, type=L\n size=+\n' | sfdisk /dev/sdc
           The same as the previous example, but in named-fields format.

       echo -e 'type=swap' | sfdisk -N 3 /dev/sdc
           Set type of the 3rd partition to 'swap'.

       sfdisk --part-type /dev/sdc 3 swap
           The same as the previous example, but without script use.

       sfdisk --delete /dev/sdc 2
           Delete 2nd partition.

       echo "+,+" | sfdisk -N 3 --move-data /dev/sdc
           Enlarge 3rd partition in both directions, move start to use free space before the partition and
           enlarge the size to use all free space after to the partition, and move partition data too.

AUTHORS

       Karel Zak <kzak@redhat.com>

       The current sfdisk implementation is based on the original sfdisk from Andries E. Brouwer.

REPORTING BUGS

       For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues.

AVAILABILITY

       The sfdisk 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/>.