How to remove a GPT label in Red Hat Enterprise Linux?

Solution Unverified - Updated

Environment

  • Red Hat Enterprise Linux (RHEL) 7 and higher versions.

Issue

  • Need to remove the GPT label present on-disk

Resolution

To remove a GPT label from disk in Red Hat Enterprise Linux 7 and above versions, use the wipefs command.

  1. View the label(s) via parted, fdisk, and hexdump commands:

        # parted /dev/sdN u s p
    Model: QEMU QEMU HARDDISK (scsi)
    Disk /dev/sdN: 4194304s
    Sector size (logical/physical): 512B/512B
    Partition Table: gpt <---
    Disk Flags: 
    Number  Start  End       Size      File system  Name     Flags
     1      2048s  4192255s  4190208s               primary

    
    # fdisk -l /dev/sdN
    WARNING: fdisk GPT support is currently new, and therefore in an experimental phase. Use at your own discretion.
    Disk /dev/sdN: 2147 MB, 2147483648 bytes, 4194304 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 512 bytes
    I/O size (minimum/optimal): 512 bytes / 512 bytes
    Disk label type: gpt <---
    Disk identifier: FAC330FF-E081-4A82-90A0-E0A397D4064E
    
    #         Start          End    Size  Type            Name
     1         2048      4192255      2G  Microsoft basic primary

    
    # hexdump -C /dev/sdN | grep 'EFI PART'
    00000200  45 46 49 20 50 41 52 54  00 00 01 00 5c 00 00 00  |EFI PART....\...| <---
    7ffffe00  45 46 49 20 50 41 52 54  00 00 01 00 5c 00 00 00  |EFI PART....\...| <---

    Note the Primary GPT label at offset 0x00000200 bytes and backup at 0x7ffffe00.

  2. Print the location of the label using the wipefs tool:

    # wipefs /dev/sdN
offset               type
----------------------------------------------------------------
0x200 <---           gpt   [partition table]

  3. Specifying the offset found, remove the label with the wipefs command:

    # wipefs -o 0x200 /dev/sdN
/dev/sdN: 8 bytes were erased at offset 0x00000200 (gpt): 45 46 49 20 50 41 52 54
/dev/sdN: calling ioclt to re-read partition table: Success

  4. In case, the backup GPT table has to be cleared off, use wipefs:

    # wipefs -a -t gpt /dev/sdN
/dev/sdN: 8 bytes were erased at offset 0x00000200 (gpt): 45 46 49 20 50 41 52 54
/dev/sdN: 8 bytes were erased at offset 0x7ffffe00 (gpt): 45 46 49 20 50 41 52 54
/dev/sdN: calling ioclt to re-read partition table: Success

  5. Verify the label has been removed. At this point, the disk should be ready for use:

    # parted /dev/sdN u s p
Error: /dev/sdN: unrecognised disk label
Model: QEMU QEMU HARDDISK (scsi)                                          
Disk /dev/sdN: 4194304s
Sector size (logical/physical): 512B/512B
Partition Table: unknown <---
Disk Flags:

Important

  • Please note that fdisk will still pick up the partition table even after wiping the primary GPT label with wipefs, because PMBR will still be present on the disk.
  • The wipefs -a -t gpt,PMBR /dev/sdN command can be used to remove the PMBR and GPT label at the same time.
  • Currently, the wipefs -a -t gpt /dev/sdN will remove the PMBR, but a bug exists and is mentioned later in this solution.
  • The wipefs -a /dev/sdN command can be used, but please note that this will erase every label on the disk and should be used with care.

  1. If there is a need to manually clear the marker for the PMBR, check the offset first:

    # hexdump -C /dev/sdN | grep '55 aa'
000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa  |..............U.|

    The offset in the example above is 0x000001f0, which converted to decimal is 496. Each 00 represents 1 byte, so add 14 places(bytes) to get to the front of the two-byte 55 aa. That gives an offset of 510.

  2. Manually wipe the 55 aa using the dd tool:

    # dd if=/dev/zero of=/dev/sdN ibs=1 obs=1 seek=510 count=2
2+0 records in
2+0 records out
2 bytes (2 B) copied, 0.00080767 s, 2.5 kB/s

  3. Verify fdisk no longer prints the table

    # fdisk -l /dev/sdN
Disk /dev/sdN: 2147 MB, 2147483648 bytes, 4194304 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
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