Changing root is commonly done for performing system maintenance on systems where booting and/or logging in is no longer possible. Common examples are:

Then we mount the partitions we need and undo whatever broke your system.

Get yourself the latest Arch Linux iso

or ArcoLinux

and keep it around

These commands will be used IF

loadkeys be-latin1
mount /dev/sda3 /mnt
mount /dev/sda1 /mnt/boot/efi
arch-chroot /mnt

You can add swapon /dev/sda2 but I rarely do out of laziness and there is no issue.

Then you are in your actual computer – install, uninstall, change configs and repair your computer.

BIOS

These commands will be used IF

loadkeys be-latin1
mount /dev/sda1 /mnt
arch-chroot /mnt

You can add swapon /dev/sda2 but I rarely do out of laziness and there is no issue.

Then you are in your actual computer – install, uninstall, change configs and repair your computer.

WHAT IF …

If you did something completely different, you will need to analyze what are your partitions.

Use lsblk for that.

Let us analyze the following partitioning.

loadkeys be-latin1
mount /dev/sda2 /mnt
mount /dev/sda1 /mnt/boot/efi
arch-chroot /mnt

You can add swapon /dev/sda3 but I rarely do out of laziness and there is no issue.

How to fix a kernel not booting or is it the grub?