Home » GPT or MBR: How do I know?

GPT or MBR: How do I know?


You can use parted -l to determine the type of partition table. Eg:

$ sudo parted -l
Model: ATA TOSHIBA THNSNS25 (scsi)
Disk /dev/sda: 256GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
 1      4194kB  32.2GB  32.2GB  primary  ext4         boot
 2      32.2GB  256GB   224GB   primary  ext4

Model: ATA Hitachi HDT72101 (scsi)
Disk /dev/sdb: 1000GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system     Flags
 1      1049kB  32.2GB  32.2GB  primary  ext4            boot
 2      32.2GB  996GB   964GB   primary  ext4
 3      996GB   1000GB  4295MB  primary  linux-swap(v1)

The Partition Table field shows that I am using a msdos MBR partition table (the one still commonly used for Linux and Windows) on both disks. From the man page parted can create (and thus hopefully identify) the following types of partition table (or more broadly `disk label’):

gpt    - this is a GPT partition table
loop   - this is raw disk access without a partition table
msdos  - this is a standard MBR partition table


It is worth adding the command for listing a single partition since this is not obvious without some knowledge of parted and it can be a pain finding the data you need if there are multiple drives. For /dev/sda you would do:

parted /dev/sda print

On linux, you can check this via the gdisk tool which should be available for any distro.

gdisk -l /dev/sda

Here, /dev/sda is the device node of the physical drive, not a partition (/dev/sda1, /dev/sda2, etc. are partitions).

If you see something that includes:

Found invalid GPT and valid MBR; converting MBR to GPT format
in memory. 

You have a MBR style disk. Don’t worry, this did not do any harm.

If you don’t see this warning, you have a GPT disk, or a hybrid GPT/MBR disk. The later are used mostly on Apple machines intended to dual-boot versions of MS Windows which do not support GPT. gdisk will indicate this with:

Found valid GPT with hybrid MBR; using GPT

They may also be used in other situations where support for both styles is required.

As the OS was not specified, here is FreeBSD way of doing things.

All is done through the gpart command (short for GEOM partioner – nothing to do with GNU).

A simple gpart show would show you all the available partitions of all the disks, but you can specify the device to have a more precise look on one:

  • legacy partition layout with MBR (aka “msdos”) and BSD partition schemes (a 2-level partitioning was usually required for BSD systems, unless using the full disk):

    $gpart show

    =>      63  67108801  ada0  MBR  (32G)
            63  67108545     1  freebsd  [active]  (32G)
      67108608       256        - free -  (128k)
    =>       0  67108545  ada0s1  BSD  (32G)
             0   2097152       2  freebsd-swap  (1.0G)
       2097152  65011393       1  freebsd-ufs  (31G)
  • modern partition layout using GPT:

    $gpart show /dev/ada2

    =>       34  976773101  ada2  GPT  (465G)
             34          6        - free -  (3.0k)
             40        128     1  freebsd-boot  (64k)
            168   67108864     2  freebsd-swap  (32G)
       67109032  901775360     3  freebsd-zfs  (430G)

To know more, all is in the gpart manual.

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