Comment 12 for bug 1800153

Every time I commission the PPC host we have in our CI I always get a GPT partitioning table using MAAS 2.4.2+. Looking through the source code it appears GPT is always set when creating a new partitioning table[1] and when generating the preseed[2] due to the bios_boot_method being powernv. I'm not sure how msdos got set but I believe the partition table type is a red herring.

The issue appears to be that Curtin is not wiping the PReP partition(/dev/sda1). If I chroot into the deployment environment and try to install GRUB with

grub-install --target=powerpc-ieee1275 /dev/sda1 --no-nvram

it fails. If I wipe /dev/sda1 first GRUB installation succeeds. I can then retry deployment and deployment works fine. I suspect the issue has to do with a newer version of GRUB being installed. Previous versions of GRUB must of been similar enough that the PReP partition didn't have to be fully wiped before installing.

@Ryan, as you mentioned Curtin has a bug where it is not fully wiping the PReP partition which appears to be the root cause of this bug. It may be worth modifying Curtin to always wipe any partition with the 'prep' flag set regardless of what wipe is set to to ensure this doesn't happen in other environments.

[1] https://git.launchpad.net/maas/tree/src/maasserver/models/partitiontable.py#n152
[2] https://git.launchpad.net/maas/tree/src/maasserver/preseed_storage.py#n254