DragonFly On-Line Manual Pages
GPT(8) DragonFly System Manager's Manual GPT(8)
gpt - GUID partition table maintenance utility
gpt [general_options] command [command_options] device ...
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.
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.
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, the name of the disk slice for the added
partition is printed. By default, it will create a dfly
partition covering the first available block of an unused disk
space. The command-specific options can be used to control this
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 efi, swap, ufs,
hfs, linux, dfly, hammer, hammer2 and windows as aliases for the
most commonly used partition types. ufs is a FreeBSD UFS UUID.
dfly has the alias dragonfly and is a DragonFly disklabel64(5)
UUID. You may also specify any symbolic name in the system
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 sizes).
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
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 disklabel -x and
hammer2 growfs are run.
gpt init -f [-B] [-E] device ...
The init command allows the user to create a new GPT similar to
the create command, but will also populate it with a boot slice
(s0) and a DragonFly slice (s1). The boot slice will be dos-
formatted. The disklabel 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, /boot/bootx64.efi will be copied
into the msdos slice (s0), and the disklabel will be initialized
with -B in addition to the normal -r -w.
If the -E option is specified, the drive is TRIMed prior to the
installation of the new label, if supported. The operation will
continue if not supported. Note that this will complete destroy
the contents of the drive.
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 number. Partition numbers start at 0.
The -s count option selects all partitions that have the given
size. This can cause multiple partitions to be removed.
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
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 the dash or minus sign (-), 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,
/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.
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
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
gpt add -i5 -t "DragonFly HAMMER" ad6
To print the contents of the GPT:
gpt show ad6
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
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
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"'
The GPT that gpt manipulates is part of the EFI standard and is supported
by many OSs. GPT uses 64 bits to store number of sectors, this supports
very large disks. With the prevalent sector size of 512B this is 8
uuid(3), disklabel64(5), uuids(5), boot0cfg(8), disklabel(8),
disklabel64(8), fdisk(8), mount(8), newfs(8), newfs_hammer(8), swapon(8)
The gpt utility appeared in FreeBSD 5.0 for ia64. It was imported to
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 5.9-DEVELOPMENT March 2, 2019 DragonFly 5.9-DEVELOPMENT