Ubuntu – Update grub in a chroot environment with root on a luks encrypted volume

chrootgrub2luks

I want to move a system (all systems I am using are Ubuntu 16.04 based) from an unencrypted partition to a luks encrypted one (on the same disk).

To this end, I created a LUKS encrypted logical volume that contains a root and a swap partition. Then I copied the content of the existing partition to the new root partition using dd.
I have checked that this new root contains the proper directory structure and performed a disk scan of the partition.

The plan was to chroot to the new system and to update grub from there.

In detail, I am trying the following (which is a combination from Ubuntu help pages and How to reinstall grub from a liveUSB if the / partition is encrypted and there is a separate /boot partition? ):

# Unlock crypto file system
sudo cryptsetup luksOpen /dev/sda2 lukslvm 

sudo vgscan 
sudo vgchange -ay
sudo svscan

# Mount root file system
sudo mount /dev/mapper/vgubuntu-root /mnt
# Mount boot filesystem
sudo mount /dev/sda1 /mnt/boot
# Mount required internal file systems
sudo mount -o rbind /dev /mnt/dev
sudo mount -t proc proc /mnt/proc
sudo mount -t sysfs sys /mnt/sys
## Additional LVM directories (for older systems)
sudo mount -o rbind /run/lvm /mnt/run/lvm
sudo mount -o rbind /run/lock/lvm /mnt/run/lock/lvm
# Enable DNS resolution
sudo cp /etc/resolv.conf /mnt/etc/resolv.conf
# Change to the encrypted system
sudo chroot /mnt /bin/bash

# Install required software
sudo apt-get install cryptsetup lvm2

# Edit /etc/crypttab
sudo printf "lukslvm\tUUID=%s\tnone\tluks\n" "$(cryptsetup luksUUID /dev/sda2)" | tee -a /etc/crypttab

# /etc/modules editieren
sudo echo "dm-crypt" >> /etc/modules

# Update kernel initramfs
sudo update-initramfs -u -k all

echo "Edit /etc/default/grub as GRUB_CMDLINE_LINUX_DEFAULT=\"kopt=root=/dev/mapper/vgubuntu-root\""
sudo vi /etc/default/grub

sudo update-grub

# Leave chroot environment
exit
# Write buffers to disk
sudo sync
# Unmount file systems
sudo umount /mnt/run/lvm
sudo umount /mnt/run/lock/lvm
sudo umount /mnt/sys
sudo umount /mnt/proc
sudo umount /mnt/boot
#
sudo swapoff -a

Unfortunately, it does not work out that way as update-grub does not seem to find the system installed on the encrypted partition.
It only find the existing installation on a different partition /dev/sda3.

What am I missing?

Best Answer

I looks like you forgot to create a proper /etc/mtap file

sudo cp /proc/mounts /mnt/etc/mtab

See https://wiki.sabayon.org/index.php?title=HOWTO:_Restore_Grub2

Related Question