How to ask curtin to use GPT instead of MBR with MAAS?

Question

I'm deploying AMD64 nodes with a 3TB first disk with MAAS but I only get a 2TB partition because curtin uses MBR instead of GPT for the partitioning.

kiko · Answer 1 · 2015-07-10 14:54:21Z

Curtin tries to choose the most appropriate partition table type for a given node:

For systems that are booting in BIOS mode, it defaults to an MBR-stored DOS partition table
For systems that are booting in UEFI mode (including ARMv8-based UEFI-enabled systems like Cavium Thunder and APM X-Gene) it defaults to a GPT partition table

Therefore, the easiest way to get a GPT partition table is to configure the node to boot in UEFI mode, which is supported starting with MAAS 1.5.

There are two additional ways to get curtin to create GPT partitions:

You can modify the curtin configuration provided by MAAS to curtin in /etc/maas/preseeds/curtin_userdata to include:
```
block-meta:
    format: gpt
```
If you have up to 4 partitions, you can easily convert DOS partition tables to GPT partitions post-installation. Curtin makes an effort to leave enough space in the partitioning to allow the conversion to successfully happen, and from r224 onwards it ensures it. Converting can be done with:
```
sgdisk --mbrtogpt <device>
```

Unfortunately, on MAAS 2.0 at least, if you convert an MBR partition on a boot disk to GPT using sgdisk, the system appears to be rendered unbootable. — nturner, Aug 23 '16 at 17:09

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