Partition table type is not selectable. MBR is forced for drives < 2TB in non-uefi systems.

Bug #1737436 reported by Daniel Keith on 2017-12-10
26
This bug affects 4 people
Affects Status Importance Assigned to Milestone
MAAS
Medium
Unassigned

Bug Description

MBR partition is forced any time a drive is < 2Tb in non-uefi systems.

I tried setting the partition table type to GPT for a node in the "Ready" state and the request was ignored -- not sure how to force GPT without just changing it after install(which causes problems with automation)

What I would expect to work:

> maas maasadmin block-device update 753 partition_table_type=GPT

gives me a "success" message but the type remains "MBR"

Likely relevant code at https://github.com/maas/maas/blob/2.3.0/src/maasserver/models/partitiontable.py#L164-L194 (thank you, Dimitrii)

Björn Tillenius (bjornt) wrote :

I believe we also need to change curtin, since it doesn't allow specifying the partition table type for the boot disk.

Changed in maas:
importance: Undecided → Medium
status: New → Triaged
milestone: none → 2.4.x
Ryan Harper (raharper) wrote :

Curtin allows specifying[1] both. For bootable GPT, you just need a bios_grub partition

Here's a GPT boot config:

storage:
 version: 1
 config:
   - id: sda
     type: disk
     ptable: gpt
     serial: dev_vda
     name: main_disk
     wipe: superblock
     grub_device: true
   - id: bios_boot
     type: partition
     size: 1M
     number: 2
     device: sda
     flag: bios_grub

The 'grub_device: true' marks the disk for grub to install itself into. And since 'ptable' is 'gpt' then grub requires a bios_grub partition, this is handled by adding the flag 'bios_grub' to the 1MB partition added to the disk.

1. http://curtin.readthedocs.io/en/latest/topics/storage.html#disk-command

Andrea Ieri (aieri) wrote :

This seems to only apply to the device flagged as bootable.
I was investigating why half of my RAID1 uses MBR and the other half uses GPT and this seems to be the reason.

You can work around this by setting/unsetting the boot flag before creating partitions, but of course that's not optimal.

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