Re: Question: GPT GUID for dm-integrity separate metadata partition

On Sun, May 31, 2026 at 09:46:45PM +0200, Max Gautier wrote:
> While setting up my system (new RAID array on top of dm-integrity on
> each RAID member), I asked myself what GPT type those separate integrity
> partition should have, to avoid being confused as something else by
> other tooling.
> (for example systemd auto-mount some partition type, so I suppose some
> other tooling could have similar behavior)

For decades, partition type GUIDs have been mostly cosmetic on Linux.
The kernel doesn't use them to decide anything - it probes
filesystem/device content directly. The partition type is just
metadata, "nice to have" for documentation purposes.

The one notable exception is systemd's Discoverable Partitions
Specification, which defines specific GUIDs for root, /usr, /home,
swap, etc. Tools like systemd-gpt-auto-generator use these to
auto-discover and auto-mount partitions.

For your case, "Linux reserved" (8DA63339-0007-60C0-C436-083AC8230908)
seems like a reasonable choice. It's recognized by partitioning tools
(fdisk, gdisk) but is not part of the Discoverable Partitions
Specification, so systemd won't try to auto-discover or auto-mount it.

    Karel

-- 
 Karel Zak  <[email protected]>
 http://karelzak.blogspot.com