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🔁 Migrate from UEFI to (Legacy) BIOS
Tuesday 28 February 2023 4 versions

Migrating Grub from a UEFI system to a BIOS (legacy) system 🔁

The general steps are:

  • Boot the computer using a live boot image - Eg. System Rescue Image
  • Mount the root filesystem1
  • Bind mount /dev, /sys, /proc and /run2
  • Change your EFI boot partition to EF02 BIOS boot partition3
  • Chroot into the mounted file-system
  • Re-install Grub 4

Here is someone who has documented this process in good detail:

Grub Install and Btrfs Root File System | Logan's Note

https://logan.tw/posts/2015/05/17/grub-install-and-btrfs-root-file-system/

#grub #seabios #coreboot #uefi

  1. Mounting BTRFS subvolumes needs an extra option ↩︎

  2. for f in dev sys proc run; do mount --bind /$f /mnt/$f; done ↩︎

  3. Remember to use gdisk if you have a GPT partition table. The BIOS boot partition code is EF02 ↩︎

  4. grub-install /dev/sda ↩︎

See Also