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ancorgs/boot-spec.md

Last active July 14, 2016 11:50
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boot-spec.md

needed_partitions in a PPC64 system

  • in a non-PowerNV system (KVM/LPAR)
    • with a partitions-based proposal
      • if there are no PReP partitions
        • requires only a PReP partition
      • if the existent PReP partition is not in the target disk
        • requires only a PReP partition
      • if there is already a PReP partition in the disk
        • does not require any particular volume
    • with a LVM-based proposal
      • if there are no PReP partitions
        • requires /boot and PReP partitions
      • if the existent PReP partition is not in the target disk
        • requires /boot and PReP partitions
      • if there is already a PReP partition in the disk
        • only requires a /boot partition
  • in bare metal (PowerNV)
    • with a partitions-based proposal
      • does not require any particular volume
    • with a LVM-based proposal
      • requires only a /boot partition
  • when proposing a boot partition
    • requires /boot to be ext4 with at least 100 MiB
    • requires /boot to be in the system disk out of LVM
    • recommends /boot to be 200 MiB
  • when proposing a PReP partition
    • requires it to be between 256KiB and 8MiB, despite the alignment
    • recommends it to be 1 MiB
    • requires it to be out of LVM
    • requires it to be bootable (ms-dos partition table)

needed_partitions in a x86 system

  • using UEFI
    • with a partitions-based proposal
      • if there are no EFI partitions
        • requires only a new /boot/efi partition
      • if there is already an EFI partition
        • only requires to use the existing EFI partition
    • with a LVM-based proposal
      • if there are no EFI partitions
        • requires only a new /boot/efi partition
      • if there is already an EFI partition
        • only requires to use the existing EFI partition
  • not using UEFI (legacy PC)
    • with GPT partition table
      • in a partitions-based proposal
        • if there is no GRUB partition
          • only requires a new GRUB partition
        • if there is already a GRUB partition
          • does not require any particular volume
      • in a LVM-based proposal
        • if there is no GRUB partition
          • only requires a new GRUB partition
        • if there is already a GRUB partition
          • does not require any particular volume
    • with an MS-DOS partition table
      • if the MBR gap is big enough to embed Grub
        • in a partitions-based proposal
          • does not require any particular volume
        • in a LVM-based proposal
          • if the MBR gap has additional space for grubenv
            • does not require any particular volume
          • if the MBR gap has no additional space
            • requires only a /boot partition [1]
      • with too small MBR gap or with no MBR gap at all
        • in a partitions-based proposal
          • if proposing root (/) as Btrfs
            • does not require any particular volume
          • if proposing root (/) as non-Btrfs
            • raises an exception [2]
        • in a LVM-based proposal
          • raises an exception
    • when proposing a boot partition
      • requires /boot to be ext4 with at least 100 MiB
      • requires /boot to be in the system disk out of LVM
      • recommends /boot to be 200 MiB
    • when proposing an new EFI partition
      • requires /boot/efi to be vfat with at least 33 MiB
      • requires /boot/efi to be out of LVM
      • recommends /boot/efi to be 500 MiB
      • requires /boot/efi to be close enough to the beginning of disk
    • when proposing an new GRUB partition
      • requires it to have the correct id
      • requires it to be out of LVM
      • requires it to be between 256KiB and 8MiB, despite the alignment
      • recommends it to be 1 MiB

[1] Needed for hibernation to work

[2] There is a chance that Grub2 can still be installed using blocklist mode, but IMHO it makes no much sense for us to propose a fragile layout. Users can still use expert partitioner and we will not prevent them to continue.

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