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Pilot6
Asked: 2019-08-09 07:29:29 +0800 CST

How do I move /boot to a separate partition on UEFI system with current boot on btrfs?

  • 772

I have Ubuntu 18.04 installed on a UEFI system with /boot on a btrfs partition (subvol=@).

Because of recent changes in Ubuntu I always get grub timeout 30 sec. This is by design if /boot is on a btrfs partition.

Part of /grub.cfg

function recordfail {
  set recordfail=1
  # GRUB lacks write support for btrfs, so recordfail support is disabled.
}
...
if [ "${recordfail}" = 1 ] ; then
  set timeout=30

I think that if I create a separate ext2 /boot partition the problem will be solved.

The question is if the above assumption is correct, how do I move boot from a btrfs subvol to an ext2 partition?

btrfs boot uefi boot-partition

2 Answers

  1. Best Answer

    I managed to do it using Boot-repair from a LiveUSB.

    Before start I recommend to create a snapshot of @ subvolume in case something goes wrong.

    1. Shrink / partition to leave 1-2 GB free with gparted

    2. Create ext2 partition.

    3. Mount the / partition to /mnt

    4. Mount the new ext2 partition to /media

    5. Run cp -a /mnt/@/boot/* /media

    6. Edit /mnt/@/etc/fstab and add there mount of the new ext2 partition to /boot.

    7. Delete old boot from / by sudo rm -r /mnt/@/boot

    8. Run sudo umount /mnt && sudo umount /media

    9. Run boot-repair and do a default check.

    All should work, and grub timeout is OK now.

    • 4

  2. There is another way to fix timeout issue on btrfs file systems.

    You can add

    GRUB_RECORDFAIL_TIMEOUT=0

    to /etc/default/grub and run sudo update-grub.

    But make sure you can always get into UEFI settings using ESC or other key.

    • 0