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 terminal (stdin refers to a
terminal).
Since version 2.26 sfdisk supports MBR (DOS), GPT, SUN and SGI disk la-
bels, 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 (since version 2.26) aligns the start and end of partitions to
block-device I/O limits when relative sizes are specified, when the de-
fault 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 align all par-
titions 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 de-
fault 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 another 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 exclusive flock for the whole-disk device to serialize device
access. The exclusive lock will cause udevd to skip the event handling
on the device. For example:
flock /dev/sdc sfdisk /dev/sdc
Note, this semantic is not currently supported by udevd for MD and DM
devices.
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 in-
put 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
GPT label is detected than sfdisk prints warning and automati-
cally enter 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 TA-
BLE.
-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 com-
mand can be used together with --verify.
-F, --list-free [device...]
List the free unpartitioned areas on all or the specified de-
vices.
--part-attrs device partition-number [attributes]
Change the GPT partition attribute bits. If attributes is not
specified, then print the current partition settings. The at-
tributes argument is a comma- or space-delimited list of bits.
The currently supported attribute bits are: RequiredPartition,
NoBlockIOProtocol, LegacyBIOSBootable and GUID-specific bits in
the range from 48 to 63. For example, the string "RequiredPar-
tition,50,51" sets three bits.
--part-label device partition-number [label]
Change the GPT partition name (label). If label is not speci-
fied, 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, or a GUID for GPT. For backward compatibility the op-
tions -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.
-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 la-
bel specified by --label.
-V, --verify [device...]
Test whether the partition table and partitions seem correct.
OPTIONS
-a, --append
Don't create a new partition table, but only append the speci-
fied partitions.
-b, --backup
Back up the current partition table sectors before starting the
partitioning. The default backup file name is ~/sfdisk-<de-
vice>-<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.
-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 re-
orders 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 fsync system call after each write when move 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 op-
tion is not supported when using the --show-size command.
-X, --label type
Specify the disk label type (e.g., dos, gpt, ...). If this op-
tion is not given, then sfdisk defaults to the existing label,
but if there is no label on the device yet, then the type de-
faults to dos. The default or the current label may be overwrit-
ten by the "label: <name>" script header line. The option --la-
bel 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 to edit 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. In all cases detected
signatures are reported by warning messages before a new parti-
tion 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 op-
tion 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 warn-
ing 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 parti-
tions.
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 spe-
cific 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 ig-
nored. 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 sin-
gle partition) is given, the default for each field is its pre-
vious value.
The default value of start is the first non-assigned sector
aligned according to device I/O limits. The default start off-
set for the first partition is 1 MiB. The offset may be fol-
lowed 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 inter-
preted 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 possi-
ble. 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), without the 0x
prefix, a GUID string for GPT, or a shortcut:
L Linux; means 83 for MBR and
0FC63DAF-8483-4772-8E79-3D69D8477DE4 for GPT.
S swap area; means 82 for MBR and 0657FD6D-
A4AB-43C4-84E5-0933C84B4F4F for GPT
E extended partition; means 5 for MBR
H home partition; means
933AC7E1-2EB4-4F13-B844-0E14E2AEF915 for GPT
X linux extended partition; means 85 for MBR.
U EFI System partition, means EF for MBR and
C12A7328-F81F-11D2-BA4B-00A0C93EC93B for GPT
R Linux RAID; means FD for MBR and
A19D880F-05FC-4D3B-A006-743F0F84911E for GPT
V LVM; means 8E for MBR and
E6D6D379-F507-44C2-A23C-238F2A3DF928 for GPT
The default type value is L
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 to
specify additional information (e.g., a UUID). It is recom-
mended 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 to specify the parti-
tions 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 attri-
bute 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 par-
tition, a GUID for a GPT partition, or a shortcut
as for unnamed-fields format. For backward com-
patibility 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 par-
tition 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-col-
ors.d/sfdisk.disable.
See terminal-colors.d(5) for more details about colorization configura-
tion. The logical color names supported by sfdisk are:
header The header of the output tables.
warn The warning messages.
welcome
The welcome message.
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-ex-
tended, --unhide, --show-extended, --cylinders, --heads, --sectors,
--inside-outer, --not-inside-outer options.
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.
SEE ALSO
fdisk(8), cfdisk(8), parted(8), partprobe(8), partx(8)
AUTHOR
Karel Zak <kzak@redhat.com>
The current sfdisk implementation is based on the original sfdisk from
Andries E. Brouwer.
AVAILABILITY
The sfdisk command is part of the util-linux package and is available
from https://www.kernel.org/pub/linux/utils/util-linux/.
util-linux June 2015 SFDISK(8)