repairing boot for LUKS encrypted fs

repair_boot.md

Guides:

• https://stephentanner.com/restoring-grub-for-an-encrypted-lvm.html
• https://askubuntu.com/questions/719409/how-to-reinstall-grub-from-a-liveusb-if-the-partition-is-encrypted-and-there-i
• https://help.ubuntu.com/community/Grub2/Installing

cryptsetup luksOpen /dev/sdb3 home_sdb3
vgchange -ay
lvscan
mkdir /media/linux
mount /dev/ubuntu-vg/root /media/linux/
mount -o bind /proc /media/linux/proc
mount -o bind /dev /media/linux/dev
mount -o bind /sys /media/linux/sys
chroot /media/linux /bin/bash

> fdisk -l:

Disk /dev/sdb: 238.5 GiB, 256060514304 bytes, 500118192 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: ED00E611-2AA0-40CB-BA69-97B8FAD3303E

Device       Start       End   Sectors   Size Type
/dev/sdb1     2048   1050623   1048576   512M EFI System
/dev/sdb2  1050624   2050047    999424   488M Linux filesystem
/dev/sdb3  2050048 500117503 498067456 237.5G Linux filesystem

mount /dev/sdb2 /boot
mount /dev/sdb1 /boot/efi

grub-install /dev/sdb
**OR** grub-update

umount /boot/efi
umount /boot

leave chroot

exit 

umount /media/linux/boot/efi
umount /media/linux/boot
umount -l /media/linux
vgchange -an
cryptsetup luksClose home_sdb3

Thanks a lot, this has saved my installation! :-)
(with small adaptations for XUbuntu 20.04 live USB as the vg root directory was automatically mounted under /media/xubuntu/ )

btw, as efi & boot were already unmounted under the chroot, shouldn't the following:

umount /media/linux/boot/efi
umount /media/linux/boot

be rather:

umount /media/linux/proc
umount /media/linux/dev
umount /media/linux/sys

?

Thank you so much for this! I would have been completely lost without it. As the first reply suggests, knowing the correct label for the LUKS partition is necessary for this to work. I actually just checked another system with Linux Mint on an NVMe drive to find it. It was nvme0n1p3_crypt

edit Just in case anyone else would run into the same situation I did, while this worked to get back into my OS, whenever I was running kernel updates, nothing was changing in the grub menu. I was racking my brain trying to figure out why, and it turned out that my /etc/fstab was missing the mount point for /boot at the UUID of /dev/nvme0n1p2.

Amazing, thank you!

Thanks, saved a lot of time cause of this!

Not all heroes wearing capes, THANK YOU :-) 👍

update-grub NOT "OR grub-update" as mentioned above

Thank you!!

Thank you!!! Many many thanks

Had to use "rbind" to make it work:

mount -o rbind /proc /media/linux/proc
mount -o rbind /dev /media/linux/dev
mount -o rbind /sys /media/linux/sys

Other than that it worked great ty!

@samuelcolvin Thank you so much, i had to combine a few other things because my disk is NVME. Also thanks to @themmm for the rbind. Saved me couple of days of full set up.