grub-install removes filesystem (!)

LQ496873 · 02-03-2022, 04:00 PM

I give in.. I need help! I've been trying for so long to get my LFS to boot. I wanted to use EFI but I couldn't get my NVME drive to be seen in 'BIOS' as bootable.

So I went back to the old ways.

I have grub installed on my /boot partition but when I fire up the computer grub starts and then stops with error: unknown filesystem.

After messing about for far too long trying to identify my nvme drive in grub-speak, and recreating /boot, and reinstalling grub I noticed when I issue...

Code:

grub-install --target i386-pc /dev/nvme0n1

... my fat filesystem is removed.

Code:

Model: NVMe Device (nvme)
Disk /dev/nvme0n1: 128GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system     Name  Flags
 1      1049kB  538MB   537MB                         bios_grub
 2      538MB   54.2GB  53.7GB  btrfs
 3      54.2GB  56.4GB  2147MB  linux-swap(v1)        swap

How can I change the 'Unknown filesystem' back to fat?

I've tried using things like fdisk but I just end up with an empty partition.

Any help would be very much appreciated!

colorpurple21859 · 02-03-2022, 09:52 PM

The bios-grub flag is used to tell grub where to install grub bootloader code. When grub-install was ran information at the beginning of the partition was overwritten with grub code, removing filesystem information. The files should still be there even through you cant' acess them.

Boot a systemrescue cd, remove the bios-grub flag, and use testdisk to recover the partition, then run a file system check.

grub-install may work with the --force option, if not you will need to create another empty 2mb partition flagged as bios-grub. Another option is to use lilo as it doesn't need this extra partition.

LQ496873 · 02-04-2022, 09:40 AM

Thank you.

I've tried recovering the partition but testdisk couldn't find anything. I wiped the entire drive and started over and tried with ext2 instead of fat. grub-install didn't remove the partition but now nothing gets written to /boot. I've just ended up with working but cluttered /boot on the host system. I don't understand why you have to bind /boot on the host to /mnt/lfs/boot... surely something has to be written to /boot partition on my lfs drive.

Overall, I give up!

colorpurple21859 · 02-04-2022, 05:04 PM

Quote:

I don't understand why you have to bind /boot on the host to /mnt/lfs/boot...

It really depends on how your system is setup whether or not you need to do this. I have boot partitions on my system but ignore this recommendation when installing lfs. I also use the host system bootloader to boot the lfs partition instead of running grub-install within lfs.

LQ496873 · 02-04-2022, 05:48 PM

Quote:

Originally Posted by colorpurple21859

I also use the host system bootloader to boot the lfs partition instead of running grub-install within lfs.

I think I'm just going to have to try this. I've spent yet another day on it and nothing. I completely wiped the nvme and went through all the motions from "8.59. GRUB-2.06" but following the UEFI steps. Everything installs as it should, my boot directory has the correct files and folders, the boot partition is definitely correct, grub installs without errors, efibootmgr (both inside and out of chroot) shows LFS but when I reboot into 'BIOS' it's not seen as bootable. I had more luck installing as legacy (in fact it still shows up as bootable if I enable legacy support) but no joy booting the OS. The emergency boot disk creates fine too but when I boot off it the only thing it sees is itself.

It's so frustrating! On the plus-side... I've spent more time learning about bootloaders, grub and filesystems in the past few days than I had in the last 25 years! I almost understand it now!

Thank you for your help.