GPART(8) FreeBSD System Manager's Manual GPART(8)
NAME
gpart - control utility for the disk partitioning GEOM class
SYNOPSIS
gpart add -t type [-a alignment] [-b start] [-s size] [-i index]
[-l label] [-f flags] geom
gpart backup geom
gpart bootcode [-N] [-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
gpart list
gpart status
gpart load
gpart unload
DESCRIPTION
The gpart utility is used to partition GEOM providers, normally disks.
The first argument is the action to be taken:
add Add a new partition to the partitioning scheme given by
geom. The partition type must be specified with -t type.
The partition's location, size, and other attributes will
be calculated automatically if the corresponding options
are not specified.
The add command accepts these options:
-a alignment If specified, then the gpart utility tries to
align start offset and partition size to be
multiple of alignment value.
-b start The logical block address where the partition
will begin. A SI unit suffix is allowed.
-f flags Additional operational flags. See the
section entitled OPERATIONAL FLAGS below for
a discussion about its use.
-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.
-s size Create a partition of size size. A SI unit
suffix is allowed.
-t type Create a partition of type type. Partition
types are discussed below in the section
entitled PARTITION TYPES.
backup Dump a partition table to standard output in a special
format used by the 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).
The bootcode command accepts these options:
-N Do not preserve the Volume Serial Number for
MBR. MBR bootcode contains Volume Serial
Number by default, and gpart tries to preserve
it when installing new bootstrap code. This
option skips preservation to help with some
versions of boot0(8) that do not support Volume
Serial Number.
-b bootcode
Embed bootstrap code from the file bootcode
into the partitioning scheme's metadata for
geom. 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
bootcode file must match the partitioning
scheme's requirements for file content and
size.
-f flags Additional operational flags. See the section
entitled OPERATIONAL FLAGS below for a
discussion about its use.
-i index Specify the target partition for -p partcode.
-p partcode
Write the bootstrap code from the file partcode
into the geom partition specified by -i index.
The size of the file must be smaller than the
size of the partition.
commit Commit any pending changes for geom geom. All actions are
committed by default and will not result in pending
changes. Actions can be modified with the -f flags option
so that they are not committed, but 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 all pending changes to disk.
create Create a new partitioning scheme on a provider given by
provider. The scheme to use must be specified with the -s
scheme option.
The create command accepts these options:
-f flags Additional operational flags. See the section
entitled OPERATIONAL FLAGS below for a
discussion about its use.
-n entries The number of entries in the partition table.
Every partitioning scheme has a minimum and
maximum number of entries. This option allows
tables to be created with a number of entries
that is within the limits. 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.
-s scheme Specify the partitioning scheme to use. The
kernel must have support for a particular
scheme before that scheme can be used to
partition a disk.
delete Delete a partition from geom geom and further identified by
the -i index option. The partition cannot be actively used
by the kernel.
The delete command accepts these options:
-f flags Additional operational flags. See the section
entitled OPERATIONAL FLAGS below for a
discussion about its use.
-i index Specifies the index of the partition to be
deleted.
destroy Destroy the partitioning scheme as implemented by geom
geom.
The destroy command accepts these options:
-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 type and/or label of the
partition can be modified. Not all partitioning schemes
support labels and it is invalid to try to change a
partition label in such cases.
The modify command accepts these options:
-f flags Additional operational flags. See the section
entitled OPERATIONAL FLAGS below for a
discussion about its use.
-i index Specifies the index of the partition to be
modified.
-l label Change the partition label to label.
-t type Change the partition type to type.
recover Recover a corrupt partition's scheme metadata on the geom
geom. See the section entitled RECOVERING below for the
additional information.
The recover command accepts these options:
-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. If the new size is not specified it
is automatically calculated to be the maximum available
from geom.
The resize command accepts these options:
-a alignment If specified, then the gpart utility tries to
align partition size to be a multiple of the
alignment value.
-f flags Additional operational flags. See the
section entitled OPERATIONAL FLAGS below for
a discussion about its use.
-i index Specifies the index of the partition to be
resized.
-s size Specifies the new size of the partition, in
logical blocks. A SI unit suffix is allowed.
restore Restore the partition table from a backup previously
created by the backup action and read from standard input.
Only the partition table is restored. This action does not
affect the content of partitions. After restoring the
partition table and writing bootcode if needed, user data
must be restored from backup.
The restore command accepts these options:
-F Destroy partition table on the given provider
before doing restore.
-f flags Additional operational flags. See the section
entitled OPERATIONAL FLAGS below for a
discussion about its use.
-l Restore partition labels for partitioning
schemes that support them.
set Set the named attribute on the partition entry. See the
section entitled ATTRIBUTES below for a list of available
attributes.
The set command accepts these options:
-a attrib Specifies the attribute to set.
-f flags Additional operational flags. See the section
entitled OPERATIONAL FLAGS below for a
discussion about its use.
-i index Specifies the index of the partition on which
the attribute will be set.
show Show current partition information for the specified geoms,
or all geoms if none are specified. The default output
includes the logical starting block of each partition, the
partition size in blocks, the partition index number, the
partition type, and a human readable partition size. Block
sizes and locations are based on the device's Sectorsize as
shown by gpart list.
The show command accepts these options:
-l For partitioning 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.
The unset command accepts these options:
-a attrib Specifies the attribute to clear.
-f flags Additional operational flags. See the section
entitled OPERATIONAL FLAGS below for a
discussion about its use.
-i index Specifies the index of the partition on which
the attribute will be cleared.
list See geom(8).
status See geom(8).
load See geom(8).
unload See geom(8).
PARTITIONING SCHEMES
Several partitioning schemes are supported by the gpart utility:
APM Apple Partition Map, used by PowerPC(R) Macintosh(R)
computers. Requires the GEOM_PART_APM kernel option.
BSD Traditional BSD disklabel, usually used to subdivide MBR
partitions. (This scheme can also be used as the sole
partitioning method, without an MBR. Partition editing tools
from other operating systems often do not understand the bare
disklabel partition layout, so this is sometimes called
"dangerously dedicated".) Requires the GEOM_PART_BSD kernel
option.
BSD64 64-bit implementation of BSD disklabel used in DragonFlyBSD to
subdivide MBR or GPT partitions. Requires the GEOM_PART_BSD64
kernel option.
LDM The Logical Disk Manager is an implementation of volume
manager for Microsoft Windows NT. Requires the GEOM_PART_LDM
kernel option.
GPT GUID Partition Table is used on Intel-based Macintosh
computers and gradually replacing MBR on most PCs and other
systems. Requires the GEOM_PART_GPT kernel option.
MBR Master Boot Record is used on PCs and removable media.
Requires the GEOM_PART_MBR kernel option. 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. It also prevents any type
of actions on such partitions.
VTOC8 Sun's SMI Volume Table Of Contents, used by SPARC64 and
UltraSPARC computers. Requires the GEOM_PART_VTOC8 kernel
option.
See glabel(8) for additional information on labelization of devices and
partitions.
PARTITION TYPES
Partition types are identified on disk by particular strings or magic
values. The gpart utility uses symbolic names for common partition types
so the user does not need 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. Symbolic names currently understood and used by
FreeBSD are:
apple-boot The system partition dedicated to storing boot
loaders on some Apple systems. The scheme-
specific types are "!171" for MBR,
"!Apple_Bootstrap" for APM, and
"!426f6f74-0000-11aa-aa11-00306543ecac" for
GPT.
bios-boot The system partition dedicated to second stage
of the boot loader program. Usually it is
used by the GRUB 2 loader for GPT partitioning
schemes. The scheme-specific type is
"!21686148-6449-6E6F-744E-656564454649".
efi The system partition for computers that use
the Extensible Firmware Interface (EFI). The
scheme-specific types are "!239" for MBR, and
"!c12a7328-f81f-11d2-ba4b-00a0c93ec93b" for
GPT.
freebsd A FreeBSD partition subdivided into
filesystems with a BSD disklabel. 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 filesystem. 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.
Other symbolic names that can be used with the gpart utility are:
apple-apfs An Apple macOS partition used for the Apple
file system, APFS.
apple-core-storage An Apple Mac OS X partition used by logical
volume manager known as Core Storage. The
scheme-specific type is
"!53746f72-6167-11aa-aa11-00306543ecac" for
GPT.
apple-hfs An Apple Mac OS X partition that contains a
HFS or HFS+ filesystem. The scheme-specific
types are "!175" for MBR, "!Apple_HFS" for APM
and "!48465300-0000-11aa-aa11-00306543ecac"
for GPT.
apple-label An Apple Mac OS X partition dedicated to
partition metadata that descibes disk device.
The scheme-specific type is
"!4c616265-6c00-11aa-aa11-00306543ecac" for
GPT.
apple-raid An Apple Mac OS X partition used in a software
RAID configuration. The scheme-specific type
is "!52414944-0000-11aa-aa11-00306543ecac" for
GPT.
apple-raid-offline An Apple Mac OS X partition used in a software
RAID configuration. The scheme-specific type
is "!52414944-5f4f-11aa-aa11-00306543ecac" for
GPT.
apple-tv-recovery An Apple Mac OS X partition used by Apple TV.
The scheme-specific type is
"!5265636f-7665-11aa-aa11-00306543ecac" for
GPT.
apple-ufs An Apple Mac OS X partition that contains a
UFS filesystem. The scheme-specific types are
"!168" for MBR, "!Apple_UNIX_SVR2" for APM and
"!55465300-0000-11aa-aa11-00306543ecac" for
GPT.
apple-zfs An Apple Mac OS X partition that contains a
ZFS volume. The scheme-specific type is
"!6a898cc3-1dd2-11b2-99a6-080020736631" for
GPT. The same GUID is being used also for
illumos/Solaris /usr partition. See CAVEATS
section below.
dragonfly-label32 A DragonFlyBSD partition subdivided into
filesystems with a BSD disklabel. The scheme-
specific type is
"!9d087404-1ca5-11dc-8817-01301bb8a9f5" for
GPT.
dragonfly-label64 A DragonFlyBSD partition subdivided into
filesystems with a disklabel64. The scheme-
specific type is
"!3d48ce54-1d16-11dc-8696-01301bb8a9f5" for
GPT.
dragonfly-legacy A legacy partition type used in DragonFlyBSD.
The scheme-specific type is
"!bd215ab2-1d16-11dc-8696-01301bb8a9f5" for
GPT.
dragonfly-ccd A DragonFlyBSD partition used with
Concatenated Disk driver. The scheme-specific
type is
"!dbd5211b-1ca5-11dc-8817-01301bb8a9f5" for
GPT.
dragonfly-hammer A DragonFlyBSD partition that contains a
Hammer filesystem. The scheme-specific type
is "!61dc63ac-6e38-11dc-8513-01301bb8a9f5" for
GPT.
dragonfly-hammer2 A DragonFlyBSD partition that contains a
Hammer2 filesystem. The scheme-specific type
is "!5cbb9ad1-862d-11dc-a94d-01301bb8a9f5" for
GPT.
dragonfly-swap A DragonFlyBSD partition dedicated to swap
space. The scheme-specific type is
"!9d58fdbd-1ca5-11dc-8817-01301bb8a9f5" for
GPT.
dragonfly-ufs A DragonFlyBSD partition that contains an UFS1
filesystem. The scheme-specific type is
"!9d94ce7c-1ca5-11dc-8817-01301bb8a9f5" for
GPT.
dragonfly-vinum A DragonFlyBSD partition used with Logical
Volume Manager. The scheme-specific type is
"!9dd4478f-1ca5-11dc-8817-01301bb8a9f5" for
GPT.
ebr A partition subdivided into filesystems with a
EBR. The scheme-specific type is "!5" for
MBR.
fat16 A partition that contains a FAT16 filesystem.
The scheme-specific type is "!6" for MBR.
fat32 A partition that contains a FAT32 filesystem.
The scheme-specific type is "!11" for MBR.
fat32lba A partition that contains a FAT32 (LBA)
filesystem. The scheme-specific type is "!12"
for MBR.
hifive-fsbl A raw partition containing a HiFive first
stage bootloader. The scheme-specific type is
"!5b193300-fc78-40cd-8002-e86c45580b47" for
GPT.
hifive-bbl A raw partition containing a HiFive second
stage bootloader. The scheme-specific type is
"!2e54b353-1271-4842-806f-e436d6af6985" for
GPT.
linux-data A Linux partition that contains some
filesystem with data. The scheme-specific
types are "!131" for MBR and
"!0fc63daf-8483-4772-8e79-3d69d8477de4" for
GPT.
linux-lvm A Linux partition dedicated to Logical Volume
Manager. The scheme-specific types are "!142"
for MBR and
"!e6d6d379-f507-44c2-a23c-238f2a3df928" for
GPT.
linux-raid A Linux partition used in a software RAID
configuration. The scheme-specific types are
"!253" for MBR and
"!a19d880f-05fc-4d3b-a006-743f0f84911e" for
GPT.
linux-swap A Linux partition dedicated to swap space.
The scheme-specific types are "!130" for MBR
and "!0657fd6d-a4ab-43c4-84e5-0933c84b4f4f"
for GPT.
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.
ms-basic-data A basic data partition (BDP) for Microsoft
operating systems. In the GPT this type is
the equivalent to partition types fat16, fat32
and ntfs in MBR. This type is used for GPT
exFAT partitions. The scheme-specific type is
"!ebd0a0a2-b9e5-4433-87c0-68b6b72699c7" for
GPT.
ms-ldm-data A partition that contains Logical Disk Manager
(LDM) volumes. The scheme-specific types are
"!66" for MBR,
"!af9b60a0-1431-4f62-bc68-3311714a69ad" for
GPT.
ms-ldm-metadata A partition that contains Logical Disk Manager
(LDM) database. The scheme-specific type is
"!5808c8aa-7e8f-42e0-85d2-e1e90434cfb3" for
GPT.
netbsd-ccd A NetBSD partition used with Concatenated Disk
driver. The scheme-specific type is
"!2db519c4-b10f-11dc-b99b-0019d1879648" for
GPT.
netbsd-cgd An encrypted NetBSD partition. The scheme-
specific type is
"!2db519ec-b10f-11dc-b99b-0019d1879648" for
GPT.
netbsd-ffs A NetBSD partition that contains an UFS
filesystem. The scheme-specific type is
"!49f48d5a-b10e-11dc-b99b-0019d1879648" for
GPT.
netbsd-lfs A NetBSD partition that contains an LFS
filesystem. The scheme-specific type is
"!49f48d82-b10e-11dc-b99b-0019d1879648" for
GPT.
netbsd-raid A NetBSD partition used in a software RAID
configuration. The scheme-specific type is
"!49f48daa-b10e-11dc-b99b-0019d1879648" for
GPT.
netbsd-swap A NetBSD partition dedicated to swap space.
The scheme-specific type is
"!49f48d32-b10e-11dc-b99b-0019d1879648" for
GPT.
ntfs A partition that contains a NTFS or exFAT
filesystem. The scheme-specific type is "!7"
for MBR.
prep-boot The system partition dedicated to storing boot
loaders on some PowerPC systems, notably those
made by IBM. The scheme-specific types are
"!65" for MBR and
"!9e1a2d38-c612-4316-aa26-8b49521e5a8b" for
GPT.
solaris-boot A illumos/Solaris partition dedicated to boot
loader. The scheme-specific type is
"!6a82cb45-1dd2-11b2-99a6-080020736631" for
GPT.
solaris-root A illumos/Solaris partition dedicated to root
filesystem. The scheme-specific type is
"!6a85cf4d-1dd2-11b2-99a6-080020736631" for
GPT.
solaris-swap A illumos/Solaris partition dedicated to swap.
The scheme-specific type is
"!6a87c46f-1dd2-11b2-99a6-080020736631" for
GPT.
solaris-backup A illumos/Solaris partition dedicated to
backup. The scheme-specific type is
"!6a8b642b-1dd2-11b2-99a6-080020736631" for
GPT.
solaris-var A illumos/Solaris partition dedicated to /var
filesystem. The scheme-specific type is
"!6a8ef2e9-1dd2-11b2-99a6-080020736631" for
GPT.
solaris-home A illumos/Solaris partition dedicated to /home
filesystem. The scheme-specific type is
"!6a90ba39-1dd2-11b2-99a6-080020736631" for
GPT.
solaris-altsec A illumos/Solaris partition dedicated to
alternate sector. The scheme-specific type is
"!6a9283a5-1dd2-11b2-99a6-080020736631" for
GPT.
solaris-reserved A illumos/Solaris partition dedicated to
reserved space. The scheme-specific type is
"!6a945a3b-1dd2-11b2-99a6-080020736631" for
GPT.
vmware-vmfs A partition that contains a VMware File System
(VMFS). The scheme-specific types are "!251"
for MBR and
"!aa31e02a-400f-11db-9590-000c2911d1b8" for
GPT.
vmware-vmkdiag A partition that contains a VMware diagostic
filesystem. The scheme-specific types are
"!252" for MBR and
"!9d275380-40ad-11db-bf97-000c2911d1b8" for
GPT.
vmware-reserved A VMware reserved partition. The scheme-
specific type is
"!9198effc-31c0-11db-8f-78-000c2911d1b8" for
GPT.
vmware-vsanhdr A partition claimed by VMware VSAN. The
scheme-specific type is
"!381cfccc-7288-11e0-92ee-000c2911d0b2" for
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
can be marked with the bootme attribute. See gptboot(8)
for more details.
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. Multiple partitions can be marked with the
bootonce and bootme attribute pairs. See gptboot(8) for
more details.
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. See gptboot(8) for
more details.
lenovofix Setting this attribute overwrites the Protective MBR with
a new one where the 0xee partition is the second, rather
than the first record. This resolves a BIOS
compatibility issue with some Lenovo models including the
X220, T420, and T520, allowing them to boot from GPT
partitioned disks without using EFI.
The scheme-specific attributes for MBR:
active
BOOTSTRAPPING
FreeBSD supports several partitioning schemes and each scheme uses
different bootstrap code. The bootstrap code is located in a specific
disk area for each partitioning scheme, and may vary in size for
different schemes.
Bootstrap code can be separated into two types. The first type is
embedded in the partitioning scheme's metadata, while the second type is
located on a specific partition. Embedding bootstrap code should only be
done with the gpart bootcode command with the -b bootcode option. The
GEOM PART class knows how to safely embed bootstrap code into specific
partitioning scheme metadata without causing any damage.
The Master Boot Record (MBR) uses a 512-byte bootstrap code image,
embedded into the partition table's metadata area. There are two
variants of this bootstrap code: /boot/mbr and /boot/boot0. /boot/mbr
searches for a partition with the 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 for multi-booting from a user-selected partition.
A BSD disklabel is usually created inside an MBR partition (slice) with
type freebsd (see the PARTITION TYPES section). It uses 8 KB size
bootstrap code image /boot/boot, embedded into the partition table's
metadata area.
Both types of bootstrap code are used to boot from the GUID Partition
Table. First, a protective MBR is embedded into the first disk sector
from the /boot/pmbr image. It searches through the GPT for a
freebsd-boot partition (see the PARTITION TYPES section) and runs the
next bootstrap stage from it. The freebsd-boot partition should be
smaller than 545 KB. It can be located either before or after other
FreeBSD partitions on the disk. There are two variants of bootstrap code
to write to this partition: /boot/gptboot and /boot/gptzfsboot.
/boot/gptboot is used to boot from UFS partitions. gptboot searches
through freebsd-ufs partitions in the GPT and selects one to boot based
on the bootonce and bootme attributes. If neither attribute is found,
/boot/gptboot boots from the first freebsd-ufs partition. /boot/loader
(the third bootstrap stage) is loaded from the first partition that
matches these conditions. See gptboot(8) for more information.
/boot/gptzfsboot is used to boot from ZFS. It searches through the GPT
for freebsd-zfs partitions, trying to detect ZFS pools. After all pools
are detected, /boot/loader is started from the first one found set as
bootable.
The VTOC8 scheme does not support embedding bootstrap code. Instead, the
8 KBytes bootstrap code image /boot/boot1 should be written with the
gpart bootcode command with the -p bootcode option to all sufficiently
large VTOC8 partitions. To do this the -i index option could be omitted.
The APM scheme also does not support embedding bootstrap code. Instead,
the 800 KBytes bootstrap code image /boot/boot1.hfs should be written
with the gpart bootcode command to a partition of type apple-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 GPT primary metadata is stored at the beginning of the device. For
redundancy, a secondary (backup) copy of the metadata is stored at the
end of the device. As a result of having two copies, some corruption of
metadata is not fatal to the working of GPT. When the kernel detects
corrupt metadata, it marks this table as corrupt and reports the problem.
destroy and recover are the only operations allowed on corrupt tables.
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 the 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.allow_nesting: 0
By default, some schemes (currently BSD, BSD64 and VTOC8) do not
permit further nested partitioning. This variable overrides this
restriction and allows arbitrary nesting (except within
partitions created at offset 0). Some schemes have their own
separate checks, for which see below.
kern.geom.part.auto_resize: 1
This variable controls automatic resize behavior of the PART GEOM
class. When this variable is enable and new size of provider is
detected, the schema metadata is resized but all changes are not
saved to disk, until gpart commit is run to confirm changes.
This behavior is also reported with diagnostic message:
GEOM_PART: (provider) was automatically resized. Use `gpart
commit (provider)` to save changes or `gpart undo (provider)` to
revert them.
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).
kern.geom.part.gpt.allow_nesting: 0
By default the GPT scheme is allowed only at the outermost
nesting level. This variable allows this restriction to be
removed.
kern.geom.part.ldm.debug: 0
Debug level of the Logical Disk Manager (LDM) module. This can
be set to a number between 0 and 2 inclusive. If set to 0
minimal debug information is printed, and if set to 2 the maximum
amount of debug information is printed.
kern.geom.part.ldm.show_mirrors: 0
This variable controls how the Logical Disk Manager (LDM) module
handles mirrored volumes. By default mirrored volumes are shown
as partitions with type ms-ldm-data (see the PARTITION TYPES
section). If this variable set to 1 each component of the
mirrored volume will be present as independent partition. NOTE:
This may break a mirrored volume and lead to data damage.
kern.geom.part.mbr.enforce_chs: 0
Specify how the Master Boot Record (MBR) module does alignment.
If this variable is set to a non-zero value, the module will
automatically recalculate the user-specified offset and size for
alignment with the CHS geometry. Otherwise the values will be
left unchanged.
kern.geom.part.separator:
Specify an optional separator that will be inserted between the
GEOM name and partition name. This variable is a loader(8)
tunable. Note that setting this variable may break software
which assumes a particular naming scheme.
EXIT STATUS
Exit status is 0 on success, and 1 if the command fails.
EXAMPLES
The examples below assume that the disk's logical block size is 512
bytes, regardless of its physical block size.
GPT
In this example, we will format ada0 with the GPT scheme and create boot,
swap and root partitions. First, we need to create the partition table:
/sbin/gpart create -s GPT ada0
Next, we install a protective MBR with the first-stage bootstrap code.
The protective MBR lists a single, bootable partition spanning the entire
disk, thus allowing non-GPT-aware BIOSes to boot from the disk and
preventing tools which do not understand the GPT scheme from considering
the disk to be unformatted.
/sbin/gpart bootcode -b /boot/pmbr ada0
We then create a dedicated freebsd-boot partition to hold the second-
stage boot loader, which will load the FreeBSD kernel and modules from a
UFS or ZFS filesystem. This partition must be larger than the bootstrap
code (either /boot/gptboot for UFS or /boot/gptzfsboot for ZFS), but
smaller than 545 kB since the first-stage loader will load the entire
partition into memory during boot, regardless of how much data it
actually contains. We create a 472-block (236 kB) boot partition at
offset 40, which is the size of the partition table (34 blocks or 17 kB)
rounded up to the nearest 4 kB boundary.
/sbin/gpart add -b 40 -s 472 -t freebsd-boot ada0
/sbin/gpart bootcode -p /boot/gptboot -i 1 ada0
We now create a 4 GB swap partition at the first available offset, which
is 40 + 472 = 512 blocks (256 kB).
/sbin/gpart add -s 4G -t freebsd-swap ada0
Aligning the swap partition and all subsequent partitions on a 256 kB
boundary ensures optimal performance on a wide range of media, from plain
old disks with 512-byte blocks, through modern "advanced format" disks
with 4096-byte physical blocks, to RAID volumes with stripe sizes of up
to 256 kB.
Finally, we create and format an 8 GB freebsd-ufs partition for the root
filesystem, leaving the rest of the slice free for additional
filesystems:
/sbin/gpart add -s 8G -t freebsd-ufs ada0
/sbin/newfs -Uj /dev/ada0p3
MBR
In this example, we will format ada0 with the MBR scheme and create a
single partition which we subdivide using a traditional BSD disklabel.
First, we create the partition table and a single 64 GB partition, then
we mark that partition active (bootable) and install the first-stage boot
loader:
/sbin/gpart create -s MBR ada0
/sbin/gpart add -t freebsd -s 64G ada0
/sbin/gpart set -a active -i 1 ada0
/sbin/gpart bootcode -b /boot/boot0 ada0
Next, we create a disklabel in that partition ("slice" in disklabel
terminology) with room for up to 20 partitions:
/sbin/gpart create -s BSD -n 20 ada0s1
We then create an 8 GB root partition and a 4 GB swap partition:
/sbin/gpart add -t freebsd-ufs -s 8G ada0s1
/sbin/gpart add -t freebsd-swap -s 4G ada0s1
Finally, we install the appropriate boot loader for the BSD label:
/sbin/gpart bootcode -b /boot/boot ada0s1
VTOC8
Create a VTOC8 scheme on da0:
/sbin/gpart create -s VTOC8 da0
Create a 512MB-sized freebsd-ufs partition to contain a UFS filesystem
from which the system can boot.
/sbin/gpart add -s 512M -t freebsd-ufs da0
Create a 15GB-sized freebsd-ufs partition to contain a UFS filesystem and
aligned on 4KB boundaries:
/sbin/gpart add -s 15G -t freebsd-ufs -a 4k da0
After creating all required partitions, embed bootstrap code into them:
/sbin/gpart bootcode -p /boot/boot1 da0
Deleting Partitions and Destroying the Partitioning Scheme
If a Device busy error is shown when trying to destroy a partition table,
remember that all of the partitions must be deleted first with the delete
action. In this example, da0 has three partitions:
/sbin/gpart delete -i 3 da0
/sbin/gpart delete -i 2 da0
/sbin/gpart delete -i 1 da0
/sbin/gpart destroy da0
Rather than deleting each partition and then destroying the partitioning
scheme, the -F option can be given with destroy to delete all of the
partitions before destroying the partitioning scheme. This is equivalent
to the previous example:
/sbin/gpart destroy -F da0
Backup and Restore
Create a backup of the partition table from da0:
/sbin/gpart backup da0 > da0.backup
Restore the partition table from the backup to da0:
/sbin/gpart restore -l da0 < /mnt/da0.backup
Clone the partition table from ada0 to ada1 and ada2:
/sbin/gpart backup ada0 | /sbin/gpart restore -F ada1 ada2
SEE ALSO
geom(4), boot0cfg(8), geom(8), glabel(8), gptboot(8)
HISTORY
The gpart utility appeared in FreeBSD 7.0.
AUTHORS
Marcel Moolenaar <marcel@FreeBSD.org>
CAVEATS
Partition type apple-zfs (6a898cc3-1dd2-11b2-99a6-080020736631) is also
being used on illumos/Solaris platforms for ZFS volumes.
FreeBSD 13.1-RELEASE-p6 January 26, 2022 FreeBSD 13.1-RELEASE-p6
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