DragonFly On-Line Manual Pages
GPT(8) DragonFly System Manager's Manual GPT(8)
NAME
gpt - GUID partition table maintenance utility
SYNOPSIS
gpt [general_options] command [command_options] device ...
DESCRIPTION
The gpt utility provides the necessary functionality to manipulate GUID
partition tables (GPTs), but see BUGS below for how and where
functionality is missing. GPT partitions are accessed as DragonFly disk
slices, with same number as GPT partition, 127 slices per disk device are
supported. The basic usage model of the gpt tool follows that of the
cvs(1) tool. The general options are described in the following
paragraph. The remaining paragraphs describe the individual commands
with their options. Here we conclude by mentioning that a device is
either a special file corresponding to a disk-like device or a regular
file. The command is applied to each device listed on the command line.
General Options
The general options allow the user to change default settings or
otherwise change the behaviour that is applicable to all commands. Not
all commands use all default settings, so some general options may not
have an effect on all commands.
The -p count option allows the user to change the number of partitions
the GPT can accommodate. This is used whenever a new GPT is created. By
default, the gpt utility will create space for 128 partitions (or 32
sectors of 512 bytes).
The -r option causes the gpt utility to open the device for reading only.
Currently this option is primarily useful for the show command, but the
intent is to use it to implement dry-run behaviour.
The -v option controls the verbosity level. The level increases with
every occurrence of this option. There is no formalized definition of
the different levels yet.
Commands
gpt add [-b number] [-i index] [-s count] [-t type] device ...
The add command allows the user to add a new partition to an
existing table. By default, it will create a dfly partition
covering the first available block of an unused disk space.
The -b number option allows the user to specify the starting
(beginning) sector number of the partition. The minimum sector
number is 1, but has to fall inside an unused region of disk
space that is covered by the GPT.
The -i index option allows the user to specify which (free) entry
in the GPT table is to be used for the new partition. By
default, the first free entry is selected. Entries start at
index 0 representing partition 0 of the GPT.
The -s count option allows the user to specify the size of the
partition in sectors. The minimum size is 1.
The -t type option allows the user to specify the partition type.
The type is given as an UUID, but gpt accepts the following
aliases for the most commonly used partition types:
apple-apfs Apple APFS
apple-hfs Apple HFS
apple-ufs Apple UFS
apple-zfs Apple ZFS
bios BIOS Boot (e.g., used by GRUB 2)
ccd DragonFly ccd((4))
dfly DragonFly disklabel64(5)
dragonfly An alias for dfly
efi EFI System
freebsd-legacy FreeBSD Legacy
freebsd-boot FreeBSD Boot
freebsd-swap FreeBSD Swap
freebsd-ufs FreeBSD UFS/UFS2
freebsd-zfs FreeBSD ZFS
hammer DragonFly HAMMER(5)
hammer2 DragonFly HAMMER2
label32 DragonFly disklabel32(5)
label64 DragonFly disklabel64(5)
linux Linux Data
linux-lvm Linux LVM
linux-raid Linux RAID
linux-swap Linux Swap
netbsd-ccd NetBSD CCD
netbsd-cgd NetBSD CGD
netbsd-ffs NetBSD FFSv1/FFSv2
netbsd-lfs NetBSD LFS
netbsd-swap NetBSD Swap
openbsd OpenBSD Data
swap FreeBSD Swap
ufs FreeBSD UFS/UFS2
vinum DragonFly vinum(4)
windows Microsoft Basic Data
windows-reserved Microsoft Reserved
windows-recovery Microsoft Recovery
Any symbolic name in the system uuids(5) files may also be
specified.
NOTE! If you don't specify a beginning sector with -b number, the
new partition will be aligned to 1MiB in size and position (in
case of 512 byte sector size).
gpt boot device ...
The boot command allows the user to create a small boot partition
in a freshly created GPT.
This command creates a small, 1GB boot partition as partition #0
and hacks in a special `slice 1' in the PMBR which aliases it.
The PMBR is further modified to add the necessary boot code. You
can then disklabel GPT partition #0 and mount it, placing the
contents of /boot directory within. You must add a line to
loader.conf, like
vfs.root.mountfrom="ufs:da1s1a"
which point to the actual root mount.
Your root partition may be another GPT partition and you may use
a 64 bit disklabel within that partition if you desire.
The `boot0' boot manager is used, it can be manipulated with the
boot0cfg(8) command, `packet' option usually needs to be set.
NOTE! A disk setup with the boot command may not be shared with
another OS, as it doesn't use a fully standard GPT.
WARNING! Some BIOSes may not be able to deal with this hack, your
mileage may vary.
gpt create [-fp] device ...
The create command allows the user to create a new (empty) GPT.
By default, one cannot create a GPT when the device contains a
MBR, however this can be overridden with the -f option. If the
-f option is specified, an existing MBR is destroyed and any
partitions described by the MBR are lost.
The -p option tells gpt to create only the primary table and not
the backup table. This option is only useful for debugging and
should not be used otherwise.
gpt destroy [-r] device ...
The destroy command allows the user to destroy an existing,
possibly not empty GPT.
The -r option instructs gpt to destroy the table in a way that it
can be recovered.
gpt expand device
The expand command will expand an existing GPT label to cover a
device which has grown in size, and will also expand the size of
the last GPT partition to fit. This is typically the first step
when expanding a HAMMER2 filesystem, after which commands
disklabel -x and hammer2 growfs are run.
gpt init -f [-B] [-E] device ...
The init command will create a new GPT similar to the create
command, but also populate it with a boot slice (s0) and a
DragonFly slice (s1). The boot slice (s0) will be formatted with
newfs_msdos(8). The disklabel in the DragonFly slice (s1) will
be left empty and ready to edit.
Due to the destructive nature of this directive, the -f option
must also be specified.
If the -B option is specified, the boot loader /boot/boot1.efi
will be copied into the boot slice (s0), and the disklabel will
be initialized with disklabel -r -w -B.
If the -E option is specified, the device will be first erased by
using the TRIM command, if supported. The operation will
continue if not supported. Note that this will completely
destroy the contents of the device.
gpt label [-a] <-f file | -l label> device ...
gpt label [-b number] [-i index] [-s count] [-t type] <-f file | -l
label> device ...
The label command allows the user to label any partitions that
match the selection. At least one of the following selection
options must be specified.
The -a option specifies that all partitions should be labeled.
It is mutually exclusive with all other selection options.
The -b number option selects the partition that starts at the
given block number.
The -i index option selects the partition with the given
partition index. Partition indexes start at 0.
The -s count option selects all partitions that have the given
size. This can cause multiple partitions to be labeled.
The -t type option selects all partitions that have the given
type. The type is given as an UUID or by the aliases that the
add command accepts. This can cause multiple partitions to be
labeled.
The -f file or -l label options specify the new label to be
assigned to the selected partitions. The -f file option is used
to read the label from the specified file. Only the first line
is read from the file and the trailing newline character is
stripped. If the file name is `-' (dash), the label is read from
the standard input. The -l label option is used to specify the
label in the command line. The label is assumed to be encoded in
UTF-8.
gpt migrate [-fs] device ...
The migrate command allows the user to migrate an MBR-based disk
partitioning into a GPT-based partitioning. By default, the MBR
is not migrated when it contains partitions of an unknown type.
This can be overridden with the -f option. Specifying the -f
option will cause unknown partitions to be ignored and any data
in it to be lost.
The -s option prevents migrating BSD disk labels into GPT
partitions by creating the GPT equivalent of a slice.
gpt remove [-a] device ...
gpt remove [-b number] [-i index] [-s count] [-t type] device ...
The remove command allows the user to remove any and all
partitions that match the selection. It uses the same selection
options as the label command. See above for a description of
these options. Partitions are removed by clearing the partition
type. No other information is changed.
gpt show [-glu] device ...
The show command displays the current partitioning on the listed
devices and gives an overall view of the disk contents. By
default, the GPT partition type is displayed in a user-friendly
form. If the -u option is specified, the GPT partition type is
displayed as a UUID. With the -l option, the GPT partition label
will be displayed instead of the GPT partition type. With the -g
option, the GPT partition GUID will be displayed instead of the
GPT partition type. None of the options has any effect on non-
GPT partitions. The order of precedence of the options are: -l,
-g, -u.
FILES
/boot/boot0 The default `boot0' image.
/etc/defaults/uuids A list of UUIDs and their symbolic names
provided by the OS vendor.
/etc/uuids A list of UUIDs and their symbolic names
provided by the system administrator.
EXAMPLES
To install an empty GPT on ad6:
gpt create ad6
GPT partitions are defined in number of sectors, the sector size is
usually 512B, which is assumed in the examples below, it can be found
using:
gpt -v show ad6
To add a dummy GPT partition 0:
gpt add -i0 -s16 ad6
You might want to do this to not use slice 0 for data; when GPT is not
used on a disk, slice 0 is the compatibility slice, which is used for
"dangerously dedicated" disks. For GPT slice 0 has no special meaning,
it is just the first slice on the disk.
To add a GPT partition of size approx. 100GB:
gpt add -s200000000 ad6
This will be GPT partition 1 as it is the first one free, it will be
accessible as ad6s1, which is also printed by the command. The type will
be "DragonFly Label64", it will have to be set up by disklabel64(8).
To add GPT partition 5 with type "DragonFly HAMMER" using the remaining
free space:
gpt add -i5 -t "DragonFly HAMMER" ad6
To print the contents of the GPT:
gpt show ad6
Boot Setup
To setup a disk using GPT for booting, the steps below can be used.
System is copied from an already installed disk, e.g. a hard disk or an
install CD. This example will setup disk da1 with GPT for booting, using
the boot command.
WARNING! Any previous data on disk installed to will be deleted.
gpt create -f da1
gpt boot da1
boot0cfg -s 2 da1
disklabel -B -r -w da1s0 auto
disklabel -e da1s0 # add `a: * * 4.2BSD', to add `a' partition
# with fstype `4.2BSD' covering whole slice
gpt add da1
disklabel64 -r -w da1s1 auto
disklabel64 -e da1s1 # add `b: 4G * swap', to add `b' partition
# with fstype `swap' and size 4GB,
# add `a: * * HAMMER', to add `a' partition
# with fstype `HAMMER' covering rest of slice
newfs_hammer -L ROOT /dev/da1s1a
mount_hammer /dev/da1s1a /mnt
newfs /dev/da1s0a
mkdir /mnt/boot
mount /dev/da1s0a /mnt/boot
cpdup / /mnt # copy each file system you need, e.g.
cpdup /boot /mnt/boot
cpdup /var /mnt/var
cpdup /var/tmp /mnt/var/tmp
cpdup /usr /mnt/usr
cd /mnt
vi etc/fstab # add `/dev/da1s1a / hammer rw',
# add `/dev/da1s1b none swap sw',
# add `/dev/da1s0a /boot ufs rw 1 1',
# delete lines for file systems cpdup'ed above
vi boot/loader.conf # add `vfs.root.mountfrom="hammer:da1s1a"'
cd
umount /mnt/boot
umount /mnt
COMPATIBILITY
The GPT that gpt manipulates is part of the EFI standard and is supported
by many OSes. GPT uses 64 bits to store number of sectors, this supports
very large disks. With the prevalent sector size of 512B this is 8
billion TB.
SEE ALSO
uuid(3), disklabel64(5), uuids(5), boot0cfg(8), disklabel(8),
disklabel64(8), fdisk(8), mount(8), newfs(8), newfs_hammer(8), swapon(8)
HISTORY
The gpt utility appeared in FreeBSD 5.0 for IA64. It was imported to
DragonFly 1.9.
BUGS
The development of the gpt utility is still work in progress. Many
necessary features are missing or partially implemented. In practice
this means that the manual page, supposed to describe these features, is
farther removed from being complete or useful. As such, missing
functionality is not even documented as missing. However, it is believed
that the currently present functionality is reliable and stable enough
that this tool can be used without bullet-proof footware if one thinks
one does not make mistakes.
It is expected that the basic usage model does not change, but it is
possible that future versions will not be compatible in the strictest
sense of the word. For example, the -p count option may be changed to a
command option rather than a generic option. There are only two commands
that use it so there is a chance that the natural tendency for people is
to use it as a command option. Also, options primarily intended for
diagnostic or debug purposes may be removed in future versions.
Another possibility is that the current usage model is accompanied by
other interfaces to make the tool usable as a back-end. This all depends
on demand and thus feedback.
The migrate command doesn't support DragonFly partition types.
DragonFly 6.5-DEVELOPMENT May 16, 2025 DragonFly 6.5-DEVELOPMENT