arch-chroot and btrfs – use the power of arch-chroot when your computer crashes

https://wiki.archlinux.org/title/Chroot#Running_on_Btrfs

ArcoLinux, based on Arch Linux, offers a rolling release system with the advanced filesystem, Btrfs. This setup provides snapshots, rollbacks, and efficient disk management. However, system issues may arise from failed updates or misconfigurations. This guide explains how to access and repair your system using arch-chroot and Btrfs subvolumes, without direct code snippets for easier WordPress formatting.

Prerequisites

  • A bootable ArchLinux media (USB/CD).
  • A basic understanding of the Linux command line.

Step 1: Identify Your Disk Partitions

Start by booting from the ArcoLinux media and opening a terminal. Use the lsblk command to list all block devices, focusing on the root partition, typically /dev/sda2 on a single-disk system.

Step 2: Mount Btrfs Subvolumes

Btrfs’s subvolumes feature allows for accessible and manageable filesystem parts. The mounting process is essential for system repair and involves several steps:

  1. Mount the root subvolume: Begin with the root subvolume, usually identified with an @ symbol.
  2. Mount other subvolumes: Continue by mounting additional subvolumes like @root, @home, @log, @cache, @tmp, and @srv at their respective directories within /mnt. This approach reflects your system’s structure for the arch-chroot operation.
  3. Mount the EFI system partition: This is crucial for EFI systems, typically involving the partition /dev/sda1.

Each mounting step involves specifying the device and the mount point, tailored to your system’s setup.

Step 3: Accessing the System with arch-chroot

With the subvolumes properly mounted, use arch-chroot to access your system in a chroot environment. This command shifts you into your system’s root environment, enabling repairs, updates, or configuration changes as if directly booted into it.

Repairing Your System

Inside the chroot environment, you can perform various system repairs:

  • Update the system: Run the system update command to ensure all packages are current.
  • Reinstall the bootloader: For EFI systems, reinstalling the bootloader may be necessary. This involves specifying the target, EFI directory, and bootloader ID.
  • Troubleshoot and modify configurations: This may include editing system files like /etc/fstab or others, according to the issues faced.

Conclusion

This guide provides a structured method for recovering an ArcoLinux system using arch-chroot and Btrfs subvolumes. By following these steps, most boot issues can be addressed efficiently, minimizing data loss. Regular backups are recommended to aid in recovery from irreversible damage.

Practice

lsblk

mount /dev/sda2 /mnt -o subvol=@
mount /dev/sda2 /mnt/root -o subvol=@root
mount /dev/sda2 /mnt/home -o subvol=@home
mount /dev/sda2 /mnt/var/log -o subvol=@log
mount /dev/sda2 /mnt/var/cache -o subvol=@cache
mount /dev/sda2 /mnt/var/tmp -o subvol=@tmp
mount /dev/sda2 /mnt/srv -o subvol=@srv

mount /dev/sda1 /mnt/boot/efi

arch-chroot /mnt