How to chroot Into a Broken Linux Installation
Here are the summary of steps:
- Boot into a Linux live installation media
- List block devices
- Mount target partition
- Change root into the mounted target partition
Boot Into a Linux Live Media
A live media is a bootable operating system usually using the most common removable media for computers like optical discs and USB flash drives. It is a working operating system that does not require any other software to boot to a computer. It allows one to run a operating system for any purpose but usually for testing new operating systems and for system maintenance.
Create a Bootable USB Drive
Download .iso file and create a bootable USB drive by executing the dd command.
The command will format the disk according to the specified or default option.
# dd if=/home/user/manjaro-xfce-16.06-x86_64.iso of=/dev/sdb bs=4M oflag=nocache,sync
If you want to see progress indicator then add the option status=progress.
List Block Devices
For simplicity, block devices refer to hard disks, usb or optical drives in a computer. We need to know the available block devices so we can mount the target partition. Once booted, we can now query for availabe block devices. There are a few ways to determine block devices in a computer but here is a couple of them:
fdisk -l
lsblk
Here is a sample output of the lsblk command.
$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 931.5G 0 disk
├─sda1 8:1 0 500.7M 0 part /boot/efi
├─sda2 8:2 0 58.6G 0 part /
├─sda3 8:3 0 29.3G 0 part
├─sda4 8:4 0 29.3G 0 part
├─sda5 8:5 0 29.3G 0 part
├─sda6 8:6 0 29.3G 0 part
├─sda7 8:7 0 58.6G 0 part
├─sda8 8:8 0 58.6G 0 part
├─sda9 8:9 0 15.6G 0 part
├─sda10 8:10 0 488.3G 0 part /mnt/stuff
└─sda11 8:11 0 134.1G 0 part /mnt/work
sdb 8:16 1 7.5G 0 disk
├─sdb1 8:17 1 1.5G 0 part
└─sdb2 8:18 1 31M 0 part
sr0 11:0 1 1024M 0 rom
Mount Target Partition
Usually it is the root partition that is the target partition that needs to be mounted.
It is common to mount external or removable drives under the /mnt directory.
sudo mount /dev/sda2 /mnt
Change root
Change root is an operation that changes the apparent root directory for the current running process and their children.
This is achieved by running the chroot command.
To be able to execute commands as if one is inside the actual Manjaro installation it is necessary to use the mhwd-chroot command.
Install the mhwd-chroot package.
sudo pacman -S mhwd-chroot
Do Your Stuff
Once, I was unable to boot into my Manjaro system after an update.
The boot process hangs at “A start job is running for CLI Netfilter Manager”.
This was related to the ufw service and therefore I needed to shut it down.
After executing chroot I disabled the service.
sudo systemctl disable ufw