SFDISK(8) System Administration SFDISK(8)
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
udevd. The recommended way how to avoid possible collisions is to use
--lock option. The exclusive lock will cause 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.
--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 section BACKING UP THE PARTITION TABLE.
-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.
--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
udevd 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!
See also --move-use-fsync.
In the example below, the first command creates a 100MiB free area
before the first partition and moves the data it contains (e.g., a
filesystem), the next command creates a new partition from the free
space (at offset 2048), and the last command reorders partitions to
match disk order (the original sdc1 will become sdc2).
echo '+100M,' | sfdisk --move-data /dev/sdc -N 1 echo '2048,' |
sfdisk /dev/sdc --append sfdisk /dev/sdc --reorder
--move-use-fsync
Use the fsync(2) system call after each write when moving data to a
new location by --move-data.
-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).
-q, --quiet
Suppress extra info messages.
-u, --unit S
Deprecated option. Only the sector unit is supported. This option
is not supported when using the --show-size command.
-X, --label type
Specify the disk label type (e.g., dos, gpt, ...). If this option
is not given, then sfdisk defaults to the existing label, but if
there is no label on the device yet, then the type defaults to dos.
The default or the current label may be overwritten by the "label:
<name>" script header line. The option --label does not force
sfdisk to create empty disk label (see the EMPTY DISK LABEL section
below).
-Y, --label-nested type
Force editing of a nested disk label. The primary disk label has to
exist already. This option allows editing for example a
hybrid/protective MBR on devices with GPT.
-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; except the old partition-table signatures which
are always wiped before create a new partition-table if the
argument when is not never. The auto mode also does not wipe the
first sector (boot sector), it is necessary to use the always mode
to wipe this area. In all cases detected signatures are reported by
warning messages before a new partition table is created. See also
the 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 after a
new partition is created. See also wipefs(8) command.
-v, --version
Display version information and exit.
-h, --help
Display help text and exit.
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:
<name>: <value>
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.
last-lba
Specify the last usable sector for GPT partitions.
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. This header is informative only and it is not
used when sfdisk creates a new partition table, in this case the
real device specific value is always used and sector size from the
dump is ignored.
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 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. The offset may be followed by the multiplicative
suffixes (KiB, MiB, GiB, TiB, PiB, EiB, ZiB and YiB) then the number is
interpreted as offset in bytes.
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 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.
The offset may be 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.
Use the --dump option 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
If you want to do a full (binary) backup of all sectors where the
partition table is stored, then use the --backup option. 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. Note that the same
concept of backup files is used by wipefs(8). For example:
sfdisk --backup /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
Note that sfdisk since version 2.26 no longer provides the -I option to
restore sectors. dd(1) provides all necessary functionality.
COLORS
Implicit coloring can be disabled by an empty file
/etc/terminal-colors.d/sfdisk.disable.
See terminal-colors.d(5) for more details about colorization
configuration. 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.
AUTHORS
Karel Zak <kzak@redhat.com>
The current sfdisk implementation is based on the original sfdisk from
Andries E. Brouwer.
SEE ALSO
fdisk(8), cfdisk(8), parted(8), partprobe(8), partx(8)
REPORTING BUGS
For bug reports, use the issue tracker at
https://github.com/karelzak/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/>.
util-linux 2.37.2 2021-07-20 SFDISK(8)
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