On 2023-10-18, Michael <[email protected]> wrote:
>> Oh, and if you use GPT, you no longer need the MBR compatibility
>> partition, or whatever its called. I no longer need it so I can't
>> remember the exact name.
>
> Man pages of partitioning tools refer to it as "Protective MBR", although
> I've
> seen it mentioned in the interwebs as "protective GPT", which I think is more
> accurate. It uses the first sector (LBA 0) to store an MBR table showing the
> whole disk, or 2TB if smaller, as an MBR partition. This is the first
> partition on the disk, typically 1 MiB in size. It is meant to stop 20 year
> old partitioning tools from messing up a GPT partitioning scheme because they
> can't see it. Arguably nobody uses Windows 98 these days, so it should be
> safe to not have a protective MBR on your GPT disks.
The protective MBR and the BIOS boot partition are two different,
unrelated things. The BIOS boot partition is a real partition (usually
1-2MB in size) that's present in the GPT parition table. It's used by
Grub as a place to store its files. It must be the first partition,
and it doesn't have a real filesystem (grub uses some sort of private
filesystem):
$ sudo fdisk -l /dev/nvme0n1
Disk /dev/nvme0n1: 465.76 GiB, 500107862016 bytes, 976773168 sectors
Disk model: Samsung SSD 980 PRO 500GB
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: E81DD16A-A5AE-3C4A-AD3C-26DF2985827A
Device Start End Sectors Size Type
/dev/nvme0n1p1 2048 6143 4096 2M BIOS boot
/dev/nvme0n1p2 6144 134219775 134213632 64G Linux filesystem
/dev/nvme0n1p3 134219776 976773134 842553359 401.8G Linux filesystem
