sfdisk

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.

       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 (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 align 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 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
              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
              GPT label is detected than sfdisk prints warning and
              automatically 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
              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.
              The currently supported attribute bits are: RequiredPartition,
              NoBlockIOProtocol, LegacyBIOSBootable and GUID-specific bits in
              the range from 48 to 63.  For example, the string
              "RequiredPartition,50,51" sets three bits.

       --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, or a GUID for GPT.  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.

       -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(1).

       -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.


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

       -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.

       -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 path overrides the default log file name (the default is
              ~/sfdisk-<devname>.move).  The log file contains information
              about all read/write operations on the partition data.

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

              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



       -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 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
              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 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.

              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), 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 ir 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 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 to specify 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, or a GUID for a GPT partition.  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.


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.


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)