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GPART(8) FreeBSD System Manager's Manual GPART(8)
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[править] NAME
gpart — control utility for the disk partitioning GEOM class
[править] SYNOPSIS
To add support for the disk partitioning GEOM class, place one or more of
the following lines in the kernel configuration file:
options GEOM_PART_APM
options GEOM_PART_BSD
options GEOM_PART_GPT
options GEOM_PART_LDM
options GEOM_PART_MBR
options GEOM_PART_EBR
options GEOM_PART_EBR_COMPAT
options GEOM_PART_PC98
options GEOM_PART_VTOC8
These options provide support for the various types of partitioning
schemes supported by the gpart utility. See PARTITIONING SCHEMES below
for more details.
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
[править] 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 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 rep‐
resent 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 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). Not all partition‐
ing 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 com‐
mitted 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 -s scheme option determines the scheme to use.
The kernel must 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 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 num‐
ber 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 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 a 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 a backup previously created by
the backup action and read from standard input. Only the par‐
tition table is restored. This action does not affect the con‐
tent of partitions. After restoring the partition table and
writing bootcode if needed, user data must be restored from
backup.
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 sec‐
tion 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 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 sec‐
tion 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.
[править] 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 parti‐
tions. (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.
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.
PC98 An MBR variant for NEC PC-98 and compatible computers. Requires
the GEOM_PART_PC98 kernel option.
VTOC8 Sun's SMI Volume Table Of Contents, used by SPARC64 and UltraSPARC
computers. Requires the GEOM_PART_VTOC8 kernel option.
[править] 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 are:
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-spe‐
cific type is "!21686148-6449-6E6F-744E-656564454649".
efi The system partition for computers that use the Extensi‐
ble Firmware Interface (EFI). In such cases, the GPT
partitioning scheme is used and the actual partition
type for the system partition can also be specified as
"!c12a7328-f81f-11d2-ba4b-00a0c93ec93ab".
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 filesys‐
tem. 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.
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-specifig type is
"!5808c8aa-7e8f-42e0-85d2-e1e90434cfb3" for GPT.
[править] 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. Parti‐
tions 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 par‐
titions 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
[править] BOOTSTRAPPING
FreeBSD supports several partitioning schemes and each scheme uses dif‐
ferent 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 embed‐
ded 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, embed‐
ded 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 boot‐
strap 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 Ta‐
ble. First, a protective MBR is embedded into the first disk sector from
the /boot/pmbr image. It searches the GPT freebsd-boot partition (see
the PARTITION TYPES section) in the GPT and runs the 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. /boot/gptboot is used to boot from
UFS. It searches freebsd-ufs GPT partitions and starts /boot/loader (the
third bootstrap stage) if found. The /boot/gptzfsboot is used to boot
from ZFS. It searches freebsd-zfs GPT partitions and starts
/boot/zfsloader if found.
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 freebsd-boot,
which should also be 800 KB in size.
[править] 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.
[править] 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 the first sector of a provider is corrupt, the kernel can not detect
GPT even if the partition table itself is not corrupt. The protective
MBR can be rewritten 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 cor‐
rupt tables.
If the size of the device has changed (e.g. volume expansion) the sec‐
ondary 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 relo‐
cates 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 cor‐
rupt. 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.
[править] 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).
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 mini‐
mal 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 sec‐
tion). If this variable set to 1 each component of the mirrored
volume will be present as independet partition. NOTE: This may
break a mirrored volume and lead to data damage.
[править] EXIT STATUS
Exit status is 0 on success, and 1 if the command fails.
[править] EXAMPLES
Create a GPT scheme on ad0:
/sbin/gpart create -s GPT ad0
Embed GPT bootstrap code into a 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 parti‐
tion must be larger than the bootstrap code (usually either /boot/gptboot
or /boot/gptzfsboot), 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. This example uses 94 blocks (47
kB) so the next partition will be aligned on a 64 kB boundary without the
need to specify an explicit offset or alignment.
/sbin/gpart add -b 34 -s 94 -t freebsd-boot ad0
/sbin/gpart bootcode -p /boot/gptboot -i 1 ad0
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 ad0
Create an MBR scheme on ada0, then create a 30GB-sized FreeBSD slice,
mark it active and install the 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 a BSD scheme (BSD label) with space for up to 20 partitions:
/sbin/gpart create -s BSD -n 20 ada0s1
Create a 1GB-sized UFS partition and a 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 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
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
[править] SEE ALSO
dd(1), geom(4), boot0cfg(8), geom(8)
[править] HISTORY
The gpart utility appeared in FreeBSD 7.0.
[править] AUTHORS
Marcel Moolenaar <marcel@FreeBSD.org>
FreeBSD 9.0 March 19, 2012 FreeBSD 9.0
