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

Provided by: fdisk_2.38.1-4ubuntu1_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.

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 (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

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/>.