gpt command¶
Synopsis¶
gpt enumerate <interface> <dev>
gpt guid <interface> <dev> [<varname>]
gpt read <interface> <dev> [<varname>]
gpt rename <interface> <dev> <part> <name>
gpt repair <interface> <dev>
gpt setenv <interface> <dev> <partition name>
gpt swap <interface> <dev> <name1> <name2>
gpt verify <interface> <dev> [<partition string>]
gpt write <interface> <dev> <partition string>
Description¶
The gpt command lets users read, create, modify, or verify the GPT (GUID Partition Table) partition layout.
Common arguments:
- interface
interface for accessing the block device (mmc, sata, scsi, usb, ….)
- dev
device number
- partition string
Describes the GPT partition layout for a disk. The syntax is similar to the one used by the mbr command command. The string contains one or more partition descriptors, each separated by a “;”. Each descriptor contains one or more fields, with each field separated by a “,”. Fields are either of the form “key=value” to set a specific value, or simple “flag” to set a boolean flag
The first descriptor can optionally be used to describe parameters for the whole disk with the following fields:
uuid_disk=UUID - Set the UUID for the disk
Partition descriptors can have the following fields:
name=<NAME> - The partition name, required
start=<BYTES> - The partition start offset in bytes, required
size=<BYTES> - The partition size in bytes or “-” to expand it to the whole free area
bootable - Set the legacy bootable flag
uuid=<UUID> - The partition UUID, optional if CONFIG_RANDOM_UUID=y is enabled
type=<UUID> - The partition type GUID, requires CONFIG_PARTITION_TYPE_GUID=y
If ‘uuid’ is not specified, but CONFIG_RANDOM_UUID is enabled, a random UUID will be generated for the partition
gpt enumerate¶
Sets the variable ‘gpt_partition_list’ to be a list of all the partition names on the device.
gpt guid¶
Report the GUID of a disk. If ‘varname’ is specified, the command will set the variable to the GUID, otherwise it will be printed out.
gpt read¶
Prints the current state of the GPT partition table. If ‘varname’ is specified, the variable will be filled with a partition string in the same format as a ‘<partition string>’, suitable for passing to other ‘gpt’ commands. If the argument is omitted, a human readable description is printed out. CONFIG_CMD_GPT_RENAME=y is required.
gpt rename¶
Renames all partitions named ‘part’ to be ‘name’. CONFIG_CMD_GPT_RENAME=y is required.
gpt repair¶
Repairs the GPT partition tables if it they become corrupted.
gpt setenv¶
The ‘gpt setenv’ command will set a series of environment variables with information about the partition named ‘<partition name>’. The variables are:
- gpt_partition_addr
the starting offset of the partition in blocks as a hexadecimal number
- gpt_partition_size
the size of the partition in blocks as a hexadecimal number
- gpt_partition_name
the name of the partition
- gpt_partition_entry
the partition number in the table, e.g. 1, 2, 3, etc.
gpt swap¶
Changes the names of all partitions that are named ‘name1’ to be ‘name2’, and all partitions named ‘name2’ to be ‘name1’. CONFIG_CMD_GPT_RENAME=y is required.
gpt verify¶
Sets return value $? to 0 (true) if the partition layout on the specified disk matches the one in the provided partition string, and 1 (false) if it does not match. If no partition string is specified, the command will check if the disk is partitioned or not.
gpt write¶
(Re)writes the partition table on the disk to match the provided partition string. It returns 0 on success or 1 on failure.
Configuration¶
To use the ‘gpt’ command you must specify CONFIG_CMD_GPT=y. To enable ‘gpt read’, ‘gpt swap’ and ‘gpt rename’, you must specify CONFIG_CMD_GPT_RENAME=y.
Examples¶
Create 6 partitions on a disk:
=> setenv gpt_parts 'uuid_disk=bec9fc2a-86c1-483d-8a0e-0109732277d7;
name=boot,start=4M,size=128M,bootable,type=ebd0a0a2-b9e5-4433-87c0-68b6b72699c7,
name=rootfs,size=3072M,type=0fc63daf-8483-4772-8e79-3d69d8477de4;
name=system-data,size=512M,type=0fc63daf-8483-4772-8e79-3d69d8477de4;
name=[ext],size=-,type=0fc63daf-8483-4772-8e79-3d69d8477de4;
name=user,size=-,type=0fc63daf-8483-4772-8e79-3d69d8477de4;
name=modules,size=100M,type=0fc63daf-8483-4772-8e79-3d69d8477de4;
name=ramdisk,size=8M,type=0fc63daf-8483-4772-8e79-3d69d8477de4
=> gpt write mmc 0 $gpt_parts
Verify that the device matches the partition layout described in the variable $gpt_parts:
=> gpt verify mmc 0 $gpt_parts
Get the information about the partition named ‘rootfs’:
=> gpt setenv mmc 0 rootfs
=> echo ${gpt_partition_addr}
2000
=> echo ${gpt_partition_size}
14a000
=> echo ${gpt_partition_name}
rootfs
=> echo ${gpt_partition_entry}
2
Get the list of partition names on the disk:
=> gpt enumerate
=> echo gpt_partition_list
boot rootfs system-data [ext] user modules ramdisk
Get the GUID for a disk:
=> gpt guid mmc 0
bec9fc2a-86c1-483d-8a0e-0109732277d7
=> gpt guid mmc gpt_disk_uuid
=> echo ${gpt_disk_uuid}
bec9fc2a-86c1-483d-8a0e-0109732277d7