BIOS Boot Support for Raw Images

[dnugmanov]

Issue Description

When attempting to deploy Kairos on Akamai Cloud (formerly Linode), the platform has specific requirements for bootable images:

• Must be a gzip-compressed RAW image
• Must have either:
  • DOS/MBR partition table, or
  • GPT partition table with legacy boot support
• UEFI booting is not supported

UEFI Raw Image Approach

Using auroraboot with --set "disk.raw=true" produces a GPT-partitioned image that appears to support BIOS booting (contains partition type EF02). However:

1. The BIOS boot partition (EF02) is completely empty (all 2mbs are zeroes)
2. The image fails to boot in BIOS mode

MBR Approach

Attempted to use undocumented option --set "disk.mbr=true" in auroraboot, but the build process stalls at:
2024-12-07T10:48:03Z INF Generating MBR disk '/tmp/auroraboot/build/disk.raw' from '/tmp/auroraboot/build/kairos.iso'

1. Legacy Boot Support with GPT

   • Are there plans to support GPT partition tables with legacy boot (EF02 partition)?
   • If yes, will this include proper GRUB installation into the BIOS boot partition?

2. MBR Image Generation

   • What is the current status of the disk.mbr=true option? Is this feature ready for use, given it's currently undocumented?
   • Can you help with a clue why the image generation got stuck at the ISO to raw conversion stage (qemu is just running vm and not stops it for saving disk )

[Itxaka]

IIRC:

• Out GPT images have legacy MBR support
• disk.mbr=true does something very special as we dont have a process to generate those images and its, it boots an iso with qemu and runs the install, then uses the disk from that qemu vm as the output.
• I dont think we tests this raw images geneartion anywhere so their status is unknown at the moment

A workaround could be to get a normal iso and qemu, run the install in the VM and get the resulting VM disk. That should contain a valid GPT-Legacy raw image that should be valid for Akamai once gzipped.

[dnugmanov]

Out GPT images have legacy MBR support

It looks like this AuroraBoot script is adapted from the Elemental Toolkit script. Interesting that the original has a TODO for legacy boot support—wonder if that's something carried over here.

[dnugmanov]

About MBR boot from @mudler:

when disk.mbr is set it will use QEMU to generate a raw image, and for that it needs a cloud config which has the following stanza:

# Automated install block
install:
  # Device for automated installs
  device: "auto"
  # Reboot after installation
  reboot: false
  # Power off after installation
  poweroff: true
  # Set to true to enable automated installations
  auto: true

My issue with being stuck on ‘Generating MBR disk’ was because I didn’t have poweroff: true after the install. The VM never stopped and didn’t return control to AuroraBoot.