• (OPTIONAL) Create a boot flash disk using android - EtchDroid USB writer | F-Droid - Free and Open Source Android App Repository
• Mounting and chrooting the system
• Edit the /etc/default/grub file
• Config and install GRUB and create the ramdisk
• References
  • [SOLVED] Grub with lvm on LUKS -> rescue mode. Incomplete grub.cfg? / Installation / Arch Linux Forums

Recently an upgrade on my notebook went bad and broke something. I wasn’t sure what went wrong but since I had just one system at that time, I had to figure out how to fix it with the help of my phone. Basically what I did is install EtchDroid to be able to download an iso and flash it to a flash drive on my phone directly. Later I could boot form that flash drive, mount the LUKS/LVM partitions and fix the bootloader. Here is a short how to.

(OPTIONAL) Create a boot flash disk using android

EtchDroid USB writer | F-Droid - Free and Open Source Android App Repository

• Source: https://f-droid.org/en/packages/eu.depau.etchdroid/
• Title: EtchDroid USB writer | F-Droid - Free and Open Source Android App Repository
• Captured on: [2021-08-05 Thu]

Mounting and chrooting the system

#+begin_src sh

cryptsetup luksOpen /dev/disk/by-partlabel/cryptlvm lvm

mount /dev/storage/root /mnt mount /dev/storage/home /mnt/home

mount /dev/sda1 /mnt/boot

cd mnt mount -t proc /proc proc #mount -t sysfs sys sys #mount -o bind dev dev mount -o bind run run

arch-chroot /mnt

dhcpcd eth0 #+end_src sh

Edit the /etc/default/grub file

#+begin_src sh

GRUB_CMDLINE_LINUX=“cryptdevice=/dev/sda2:lvm” GRUB_PRELOAD_MODULES=“part_gpt part_msdos cryptodisk luks” #+end_src sh

Config and install GRUB and create the ramdisk

#+begin_src sh

grub-mkconfig > /boot/grub/grub.cfg grub-install –efi-directory=/boot –target=x86_64-efi /dev/sda

mkinitcpio -p linux #+end_src sh

References

[SOLVED] Grub with lvm on LUKS -> rescue mode. Incomplete grub.cfg? / Installation / Arch Linux Forums

• Source: https://bbs.archlinux.org/viewtopic.php?id=246628
• Title: [SOLVED] Grub with lvm on LUKS -> rescue mode. Incomplete grub.cfg? / Installation / Arch Linux Forums
• Captured on: [2021-08-04 Wed]

I use Arch Linux and I prepared a repository with my custom install method based on archinstaller. Basically I have a custom partitioning based on LVM on top of LUKS and some variables to start he installing method.

Here is an overview of the parts on this tutorial:

Tutorial overview

1. Create a bootable USB and boot the broken system with it (AKA recovery mode**
2. Chroot into the system
3. Fix the issue

Assumptions

I will assume that the error is similar as mine. After opening the LUKS device, I had the following problem: ERROR: device /dev/mapper/storage-root not found.

Create a bootable USB

To create a bootable USB you need to download the latest Arch Linux iso and then us dd to dump it to a flash drive.

dd bs=4M if=/path/to/archlinux.iso of=/dev/sdx status=progress && sync

After completion, use the same flash drive to boot the broken computer. You generally need to hit a key on the F5 - F6 range to choose the boot method.

Chroot into the system

Once the system has booted, now we need to mount everything the system would mount on a boot stage. Adapt the LUKS label and LVM devices according to your needs.

# Open the LUKS device.
cryptsetup luksOpen /dev/disk/by-partlabel/cryptlvm lvm

# Mount the root partition
mount /dev/storage/root /mnt

# Mount the boot partition
mount /dev/sda1 /mnt/boot

# Mount proc, sys and dev
mount -t proc proc proc/
mount -t sysfs sys sys/
mount -o bind /dev dev/

# Switch to bash
bash

# Chroot
chroot /mnt

# Bring up network if needed
dhcpcd eth0

At this point you should have shell with a recovery environment set to fix the issue, so let’s fix it.

Fix the issue

To fix the issue we basically are going to perform an upgrade an recreate the initial ramdisk

# Update the packages database
pacman -Syy

# Upgrade the packages
pacman -Syu

# Update udev package
pacman -S udev

# Update mkinitcpio package
pacman -S mkinitcpio

# Recreate the initial ramdisk
mkinitcpio -p linux

# Exit the chroot environment
exit

# Reboot
reboot

If everything went well, you now should be able to boot the system properly.

Conclusions

I was quite worried about how to solve this issue due to the several layers of complexity: GPT, LUKS and LVM, however everything went out quite smoothly. The key part is to use a USB flash drive and then mount the boot and root partitions to recreate the ramdisk.

Thanks for reading. Spot an error or want to explain something better, feel free to send me a PR.

I have been using LVM on top of LUKS for more than 2 years without problems. However since I haven’t had the chance to troubleshoot these technologies in the past I was quite concerned of what would happen when I would have problems. Today my main computer didn’t boot up and I had to fix it manually. This post shows the steps I performed to recover my system.

Intro

cryptsetup luksOpen /dev/sda2 cryptlvm

e2fsck -f /dev/mapper/storage-home

resize2fs -p /dev/mapper/storage-home 200g

e2fsck -f /dev/mapper/storage-home

(lvdisplay)
lvreduce -L -15.68G /dev/storage/home
(lvdisplay)

[lvresize -l +100%FREE /dev/storate/root]

e2fsck -f /dev/mapper/storage-root

resize2fs /dev/mapper/storage-root

cryptsetup luksClose /dev/sda2 cryptlvm


### NOT NEEDED

(pvdisplay)
pvresize --sephysicalvolumesize 218G /dev/mapper/cryptlvm

/dev/mapper/cryptlvm is active and is in use
  type:    LUKS1
  cipher:  aes-xts-plain64
  keysize: 256 bits
  device:  /dev/sda2
  offset:  4096 sectors
  size:    487981391 sectors
  mode:    read/write

NEW_SECTORS = EXISTING_SECTORS * NEW_SIZE_IN_GB / EXISTING_SIZE_IN_GB
487981391 * 200.7 / 232.7   = 420876085
(487981391 - 15*1024*1024*2 = 456524111)

cryptsetup -b 420876085 resize cryptlvm

(cryptsetup status cryptlvm)

parted /dev/sda

resize