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GPART(8)                FreeBSD System Manager's Manual               GPART(8)

NAME
     gpart - control utility for the disk partitioning GEOM class

SYNOPSIS
     To add support for the disk partitioning GEOM class, place one or more of
     the following lines in your kernel configuration file:

           options GEOM_PART_APM
           options GEOM_PART_BSD
           options GEOM_PART_EBR
           options GEOM_PART_EBR_COMPAT
           options GEOM_PART_GPT
           options GEOM_PART_MBR
           options GEOM_PART_PC98
           options GEOM_PART_VTOC8

     The GEOM_PART_APM option adds support for the Apple Partition Map (APM)
     found on Apple Macintosh computers.  The GEOM_PART_BSD option adds
     support for the traditional BSD disklabel.  The GEOM_PART_EBR option adds
     support for the Extended Boot Record (EBR), which is used to define a
     logical partition.  The GEOM_PART_EBR_COMPAT option enables backward
     compatibility for partition names in the EBR scheme.  Also it makes
     impossible any types of actions with such partitions.  The GEOM_PART_GPT
     option adds support for the GUID Partition Table (GPT) found on Intel
     Itanium computers and Intel-based Macintosh computers.  The GEOM_PART_MBR
     option adds support for the Master Boot Record (MBR) found on PCs and
     used on many removable media.  The GEOM_PART_PC98 option adds support for
     the MBR variant as used on NEC PC-98 computers.  The GEOM_PART_VTOC8
     option adds support for Sun's SMI VTOC8 label as found on computers based
     on SPARC64 and UltraSPARC.

     Usage of the gpart utility:

     gpart add -t type [-a alignment] [-b start] [-s size] [-i index]
           [-l label] [-f flags] geom
     gpart backup geom
     gpart bootcode [-b bootcode] [-p partcode -i index] [-f flags] geom
     gpart commit geom
     gpart create -s scheme [-n entries] [-f flags] provider
     gpart delete -i index [-f flags] geom
     gpart destroy [-F] [-f flags] geom
     gpart modify -i index [-l label] [-t type] [-f flags] geom
     gpart recover [-f flags] geom
     gpart resize -i index [-a alignment] [-s size] [-f flags] geom
     gpart restore [-lF] [-f flags] provider [...]
     gpart set -a attrib -i index [-f flags] geom
     gpart show [-l | -r] [-p] [geom ...]
     gpart undo geom
     gpart unset -a attrib -i index [-f flags] geom

DESCRIPTION
     The gpart utility is used to partition GEOM providers, normally disks.
     The first argument of which is the action to be taken:

     add           Add a new partition to the partitioning scheme given by
                   geom.  The partition begins on the logical block address
                   given by the -b start option.  Its size is given by the -s
                   size option.  SI unit suffixes are allowed.  One or both -b
                   and -s options can be omitted.  If so they are
                   automatically calculated.  The type of the partition is
                   given by the -t type option.  Partition types are discussed
                   below in the section entitled PARTITION TYPES.

                   Additional options include:

                   -a alignment  If specified, then gpart utility tries to
                                 align start offset and partition size to be
                                 multiple of alignment value.

                   -i index      The index in the partition table at which the
                                 new partition is to be placed.  The index
                                 determines the name of the device special
                                 file used to represent the partition.

                   -l label      The label attached to the partition.  This
                                 option is only valid when used on
                                 partitioning schemes that support partition
                                 labels.

                   -f flags      Additional operational flags.  See the
                                 section entitled OPERATIONAL FLAGS below for
                                 a discussion about its use.

     backup        Dump a partition table to standard output in special format
                   used by restore action.

     bootcode      Embed bootstrap code into the partitioning scheme's
                   metadata on the geom (using -b bootcode) or write bootstrap
                   code into a partition (using -p partcode and -i index).
                   Not all partitioning schemes have embedded bootstrap code,
                   so the -b bootcode option is scheme-specific in nature (see
                   the section entitled BOOTSTRAPPING below).  The -b bootcode
                   option specifies a file that contains the bootstrap code.
                   The contents and size of the file are determined by the
                   partitioning scheme.  The -p partcode option specifies a
                   file that contains the bootstrap code intended to be
                   written to a partition.  The partition is specified by the
                   -i index option.  The size of the file must be smaller than
                   the size of the partition.

                   Additional options include:

                   -f flags    Additional operational flags.  See the section
                               entitled OPERATIONAL FLAGS below for a
                               discussion about its use.

     commit        Commit any pending changes for geom geom.  All actions are
                   being committed by default and will not result in pending
                   changes.  Actions can be modified with the -f flags option
                   so that they are not being committed by default.  As such,
                   they become pending.  Pending changes are reflected by the
                   geom and the gpart utility, but they are not actually
                   written to disk.  The commit action will write any and all
                   pending changes to disk.

     create        Create a new partitioning scheme on a provider given by
                   provider.  The -s scheme option determines the scheme to
                   use.  The kernel needs to have support for a particular
                   scheme before that scheme can be used to partition a disk.

                   Additional options include:

                   -n entries  The number of entries in the partition table.
                               Every partitioning scheme has a minimum and a
                               maximum number of entries and this option
                               allows tables to be created with the number of
                               entries that lies anywhere between the minimum
                               and the maximum.  Some schemes have a maximum
                               equal to the minimum and some schemes have a
                               maximum large enough to be considered
                               unlimited.  By default, partition tables are
                               created with the minimum number of entries.

                   -f flags    Additional operational flags.  See the section
                               entitled OPERATIONAL FLAGS below for a
                               discussion about its use.

     delete        Delete a partition from geom geom and further identified by
                   the -i index option.  The partition cannot be actively used
                   by the kernel.

                   Additional options include:

                   -f flags    Additional operational flags.  See the section
                               entitled OPERATIONAL FLAGS below for a
                               discussion about its use.

     destroy       Destroy the partitioning scheme as implemented by geom
                   geom.

                   Additional options include:

                   -F          Forced destroying of the partition table even
                               if it is not empty.

                   -f flags    Additional operational flags.  See the section
                               entitled OPERATIONAL FLAGS below for a
                               discussion about its use.

     modify        Modify a partition from geom geom and further identified by
                   the -i index option.  Only the the type and/or label of the
                   partition can be modified.  To change the type of a
                   partition, specify the new type with the -t type option.
                   To change the label of a partition, specify the new label
                   with the -l label option.  Not all partitioning schemes
                   support labels and it is invalid to try to change a
                   partition label in such cases.

                   Additional options include:

                   -f flags    Additional operational flags.  See the section
                               entitled OPERATIONAL FLAGS below for a
                               discussion about its use.

     recover       Recover corrupt partition's scheme metadata on the geom
                   geom.  See the section entitled RECOVERING below for the
                   additional information.

                   Additional options include:

                   -f flags    Additional operational flags.  See the section
                               entitled OPERATIONAL FLAGS below for a
                               discussion about its use.

     resize        Resize a partition from geom geom and further identified by
                   the -i index option.  New partition size is expressed in
                   logical block numbers and can be given by the -s size
                   option.  If -s option is omitted then new size is
                   automatically calculated to maximum available from given
                   geom geom.

                   Additional options include:

                   -a alignment  If specified, then gpart utility tries to
                                 align partition size to be multiple of
                                 alignment value.

                   -f flags      Additional operational flags.  See the
                                 section entitled OPERATIONAL FLAGS below for
                                 a discussion about its use.

     restore       Restore the partition table from backup previously created
                   by backup action and given from standard input.  Only
                   partition table may be restored.  This action does not
                   affect content of partitions.  This mean that you should
                   copy your data from backup after restoring partition table
                   and write bootcode again if it is needed.

                   Additional options include:

                   -F          Destroy partition table on the given provider
                               before doing restore.

                   -l          Restore partition labels for partitioning
                               schemes that support them.

                   -f flags    Additional operational flags.  See the section
                               entitled OPERATIONAL FLAGS below for a
                               discussion about its use.

     set           Set the named attribute on the partition entry.  See the
                   section entitled ATTRIBUTES below for a list of available
                   attributes.

                   Additional options include:

                   -f flags    Additional operational flags.  See the section
                               entitled OPERATIONAL FLAGS below for a
                               discussion about its use.

     show          Show the current partition information of the specified
                   geoms or all geoms if none are specified.  Additional
                   options include:

                   -l          For partition schemes that support partition
                               labels print them instead of partition type.

                   -p          Show provider names instead of partition
                               indexes.

                   -r          Show raw partition type instead of symbolic
                               name.

     undo          Revert any pending changes for geom geom.  This action is
                   the opposite of the commit action and can be used to undo
                   any changes that have not been committed.

     unset         Clear the named attribute on the partition entry.  See the
                   section entitled ATTRIBUTES below for a list of available
                   attributes.

                   Additional options include:

                   -f flags    Additional operational flags.  See the section
                               entitled OPERATIONAL FLAGS below for a
                               discussion about its use.

PARTITION TYPES
     Partition types are identified on disk by particular strings or magic
     values.  The gpart utility uses symbolic names for common partition types
     to avoid the user needing to know these values or other details of the
     partitioning scheme in question.  The gpart utility also allows the user
     to specify scheme-specific partition types for partition types that do
     not have symbolic names.  The symbolic names currently understood are:

     bios-boot          The system partition dedicated to second stage of the
                        boot loader program.  Usually it used by GRUB 2 loader
                        when the partition table is GPT.  The scheme-specific
                        type is "!21686148-6449-6E6F-744E-656564454649".

     efi                The system partition for computers that use the
                        Extensible Firmware Interface (EFI).  In such cases,
                        the GPT partitioning scheme is being used and the
                        actual partition type for the system partition can
                        also be specified as
                        "!c12a7328-f81f-11d2-ba4b-00a0c93ec93ab".

     freebsd            A FreeBSD partition that uses the BSD disklabel to
                        sub-divide the partition into file systems.  This is a
                        legacy partition type and should not be used for the
                        APM or GPT schemes.  The scheme-specific types are
                        "!165" for MBR, "!FreeBSD" for APM, and
                        "!516e7cb4-6ecf-11d6-8ff8-00022d09712b" for GPT.

     freebsd-boot       A FreeBSD partition dedicated to bootstrap code.  The
                        scheme-specific type is
                        "!83bd6b9d-7f41-11dc-be0b-001560b84f0f" for GPT.

     freebsd-swap       A FreeBSD partition dedicated to swap space.  The
                        scheme-specific types are "!FreeBSD-swap" for APM,
                        "!516e7cb5-6ecf-11d6-8ff8-00022d09712b" for GPT, and
                        tag 0x0901 for VTOC8.

     freebsd-ufs        A FreeBSD partition that contains a UFS or UFS2 file
                        system.  The scheme-specific types are "!FreeBSD-UFS"
                        for APM, "!516e7cb6-6ecf-11d6-8ff8-00022d09712b" for
                        GPT, and tag 0x0902 for VTOC8.

     freebsd-vinum      A FreeBSD partition that contains a Vinum volume.  The
                        scheme-specific types are "!FreeBSD-Vinum" for APM,
                        "!516e7cb8-6ecf-11d6-8ff8-00022d09712b" for GPT, and
                        tag 0x0903 for VTOC8.

     freebsd-zfs        A FreeBSD partition that contains a ZFS volume.  The
                        scheme-specific types are "!FreeBSD-ZFS" for APM,
                        "!516e7cba-6ecf-11d6-8ff8-00022d09712b" for GPT, and
                        0x0904 for VTOC8.

     mbr                A partition that is sub-partitioned by a master boot
                        record (MBR).  This type is known as
                        "!024dee41-33e7-11d3-9d69-0008c781f39f" by GPT.

ATTRIBUTES
     The scheme-specific attributes for EBR:

     active

     The scheme-specific attributes for GPT:

     bootme          When set, the gptboot stage 1 boot loader will try to
                     boot the system from this partition.  Multiple partitions
                     might be marked with the bootme attribute.  In such
                     scenario the gptboot will try all bootme partitions one
                     by one, until the next boot stage is successfully
                     entered.

     bootonce        Setting this attribute automatically sets the bootme
                     attribute.  When set, the gptboot stage 1 boot loader
                     will try to boot the system from this partition only
                     once.  Partitions with both bootonce and bootme
                     attributes are tried before partitions with only the
                     bootme attribute.  Before bootonce partition is tried,
                     the gptboot removes the bootme attribute and tries to
                     execute the next boot stage.  If it fails, the bootonce
                     attribute that is now alone is replaced with the
                     bootfailed attribute.  If the execution of the next boot
                     stage succeeds, but the system is not fully booted, the
                     gptboot will look for bootonce attributes alone (without
                     the bootme attribute) on the next system boot and will
                     replace those with the bootfailed attribute.  If the
                     system is fully booted, the /etc/rc.d/gptboot start-up
                     script will look for partition with the bootonce
                     attribute alone, will remove the attribute and log that
                     the system was successfully booted from this partition.
                     There should be at most one bootonce partition when
                     system is successfully booted.  Multiple partitions might
                     be marked with the bootonce and bootme attribute pairs.

     bootfailed      This attribute should not be manually managed.  It is
                     managed by the gptboot stage 1 boot loader and the
                     /etc/rc.d/gptboot start-up script.  This attribute is
                     used to mark partitions that had the bootonce attribute
                     set, but we failed to boot from them.  Once we
                     successfully boot, the /etc/rc.d/gptboot script will log
                     all the partitions we failed to boot from and will remove
                     the bootfailed attributes.

     The scheme-specific attributes for MBR:

     active

     The scheme-specific attributes for PC98:

     active

     bootable

BOOTSTRAPPING
     FreeBSD supports several partitioning schemes and each scheme uses
     different bootstrap code.  The bootstrap code is located in the specific
     disk area for each partitioning scheme and also it might have different
     size.

     The bootstrap code could be separated into two types.  The first one is
     embedded in the partitioning scheme's metadata, the second type is
     located on the specific partition.  The embedding bootstrap code should
     be done only with the gpart bootcode command with -b bootcode option.
     The GEOM PART class has knowlege on how to embed bootstrap code into
     specific partitioning scheme metadata without damage.

     The Master Boot Record (MBR) uses 512-bytes bootstrap code image,
     embedded into partition table's metadata area.  There are two variants of
     this bootstrap code: /boot/mbr and /boot/boot0.  The first one searches
     partition with active attribute (see the ATTRIBUTES section) in the
     partition table.  Then it runs next bootstrap stage.  The /boot/boot0
     image contains a boot manager with some additional interactive functions.

     The BSD disklabel is usually created on top of the MBR partition (slice)
     with type freebsd (see the PARTITION TYPES section).  It uses 8 KB size
     bootstrap code image /boot/boot, embedded into partition table's metadata
     area.

     Both types of bootstrap code are used to boot from the GUID Partition
     Table.  First of all, a protective MBR is embedded into first disk sector
     from the /boot/pmbr image.  It searches the freebsd-boot partition (see
     the PARTITION TYPES section) in the GPT and runs next bootstrap stage
     from it.  The freebsd-boot partition should be smaller than 545 KB.
     There are two variants of bootstrap code to write to this partition:
     /boot/gptboot and /boot/gptzfsboot.  The first one is used to boot from
     UFS.  It searches in the GPT partition with type freebsd-ufs, and it runs
     the third bootstrap stage ( /boot/loader) if it is found.  The
     /boot/gptzfsboot is used to boot from ZFS.  It searches partition with
     type freebsd-zfs and starts /boot/zfsloader from it.

     The VTOC8 scheme does not support embedding bootstrap code.  Instead, the
     8 KBytes bootstrap code image /boot/boot1 should be written with gpart
     bootcode command with -p bootcode option to all sufficiently large VTOC8
     partitions.  To do this the -i index option could be ommited.

     The APM scheme also does not support embedding bootstrap code.  Instead,
     the 800 KBytes bootstrap code image /boot/boot1.hfs should be written
     with gpart bootcode command to a partition of type freebsd-boot, which
     should also be 800 KB in size.

OPERATIONAL FLAGS
     Actions other than the commit and undo actions take an optional -f flags
     option.  This option is used to specify action-specific operational
     flags.  By default, the gpart utility defines the `C' flag so that the
     action is immediately committed.  The user can specify ``-f x'' to have
     the action result in a pending change that can later, with other pending
     changes, be committed as a single compound change with the commit action
     or reverted with the undo action.

RECOVERING
     The GEOM PART class supports recovering of partition tables only for GPT.
     The GUID partition table has a primary and secondary (backup) copy of
     metadata for redundance, these are stored at the begining and the end of
     the device respectively.  As a result of having two copies, it is
     acceptable to have some corruption within the metadata that is not fatal
     to the working of GPT.  When the kernel detects corrupt metadata it marks
     this table as corrupt and reports the corruption.  Any operations on
     corrupt tables are prohibited except for destroy and recover.

     If the first sector of a provider is corrupt, the kernel can not detect
     GPT even if partition table itself is not corrupt.  You can rewrite the
     protective MBR using the dd(1) command, to restore the ability to detect
     the GPT.  The copy of the protective MBR is usually located in the
     /boot/pmbr file.

     If one GPT header appears to be corrupt but the other copy remains
     intact, the kernel will log the following:

           GEOM: provider: the primary GPT table is corrupt or invalid.
           GEOM: provider: using the secondary instead -- recovery strongly advised.

     or

           GEOM: provider: the secondary GPT table is corrupt or invalid.
           GEOM: provider: using the primary only -- recovery suggested.

     Also gpart commands such as show, status and list will report about
     corrupt tables.

     If the size of the device has changed (e.g. volume expansion) the
     secondary GPT header will no longer be located in the last sector.  This
     is not a metadata corruption, but it is dangerous because any corruption
     of the primary GPT will lead to loss of partition table.  This problem is
     reported by the kernel with the message:

           GEOM: provider: the secondary GPT header is not in the last LBA.

     This situation can be recovered with the recover command.  This command
     reconstructs the corrupt metadata using known valid metadata and
     relocates the secondary GPT to the end of the device.

     NOTE: The GEOM PART class can detect the same partition table visible
     through different GEOM providers, and some of them will be marked as
     corrupt.  Be careful when choosing a provider for recovery.  If you
     choose incorrectly you can destroy the metadata of another GEOM class,
     e.g. GEOM MIRROR or GEOM LABEL.

SYSCTL VARIABLES
     The following sysctl(8) variables can be used to control the behavior of
     the PART GEOM class.  The default value is shown next to each variable.

     kern.geom.part.check_integrity: 1
             This variable controls the behaviour of metadata integrity
             checks.  When integrity checks are enabled, the PART GEOM class
             verifies all generic partition parameters obtained from the disk
             metadata.  If some inconsistency is detected, the partition table
             will be rejected with a diagnostic message: GEOM_PART: Integrity
             check failed (provider, scheme).

EXIT STATUS
     Exit status is 0 on success, and 1 if the command fails.

EXAMPLES
     Create GPT scheme on ad0:

           /sbin/gpart create -s GPT ad0

     Embed GPT bootstrap code into protective MBR:

           /sbin/gpart bootcode -b /boot/pmbr ad0

     Create a dedicated freebsd-boot partition that can boot FreeBSD from a
     freebsd-ufs partition, and install bootstrap code into it.  This
     partition must be larger than /boot/gptboot, or the GPT boot you are
     planning to write, but smaller than 545 KB.  A size of 15 blocks (7680
     bytes) would be sufficient for booting from UFS but let's use 128 blocks
     (64 KB) here in this example, in order to reserve some space for
     potential future need (e.g. from a ZFS partition).

           /sbin/gpart add -b 34 -s 128 -t freebsd-boot ad0
           /sbin/gpart bootcode -p /boot/gptboot -i 1 ad0

     Create a 512MB-sized freebsd-ufs partition that would contain UFS where
     the system boots from:

           /sbin/gpart add -b 162 -s 1048576 -t freebsd-ufs ad0

     Create MBR scheme on ada0, then create 30GB-sized FreeBSD slice, mark it
     active and install boot0 boot manager:

           /sbin/gpart create -s MBR ada0
           /sbin/gpart add -t freebsd -s 30G ada0
           /sbin/gpart set -a active -i 1 ada0
           /sbin/gpart bootcode -b /boot/boot0 ada0

     Now create BSD scheme (BSD label) with ability to have up to 20
     partitions:

           /sbin/gpart create -s BSD -n 20 ada0s1

     Create 1GB-sized UFS partition and 4GB-sized swap partition:

           /sbin/gpart add -t freebsd-ufs -s 1G ada0s1
           /sbin/gpart add -t freebsd-swap -s 4G ada0s1

     Install bootstrap code for the BSD label:

           /sbin/gpart bootcode -b /boot/boot ada0s1

     Create VTOC8 scheme on da0:

           /sbin/gpart create -s VTOC8 da0

     Create a 512MB-sized freebsd-ufs partition that would contain UFS where
     the system boots from:

           /sbin/gpart add -s 512M -t freebsd-ufs da0

     Create a 15GB-sized freebsd-ufs partition that would contain UFS and
     aligned on 4KB boundaries:

           /sbin/gpart add -s 15G -t freebsd-ufs -a 4k da0

     After having created all required partitions, embed bootstrap code into
     them:

           /sbin/gpart bootcode -p /boot/boot1 da0

     Create backup of partition table from da0:

           /sbin/gpart backup da0 > da0.backup

     Restore partition table from backup to da0:

           /sbin/gpart restore -l da0 < /mnt/da0.backup

     Clone partition table from ada0 to ada1 and ada2:

           /sbin/gpart backup ada0 | /sbin/gpart restore -F ada1 ada2

SEE ALSO
     dd(1), geom(4), boot0cfg(8), geom(8)

HISTORY
     The gpart utility appeared in FreeBSD 7.0.

AUTHORS
     Marcel Moolenaar <marcel@FreeBSD.org>

FreeBSD 11.0-PRERELEASE         August 19, 2011        FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | PARTITION TYPES | ATTRIBUTES | BOOTSTRAPPING | OPERATIONAL FLAGS | RECOVERING | SYSCTL VARIABLES | EXIT STATUS | EXAMPLES | SEE ALSO | HISTORY | AUTHORS

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