How to boot from a bootable Recovery USB and recover the boot loader.

This is useful if you cannot boot your Operating System from disk.

Please note: You can follow this guide to create a bootable USB drive.

1 Cannot boot

If you can't access your operating system or its recovery menu, it can be repaired from a bootable USB drive.
Firstly, insert the USB drive and turn on your computer whilst repeatedly tapping the F7 key.
This will bring up the boot menu.

2 Boot Recovery USB

Use the arrow keys to select your USB drive and press enter to boot from it. You need to use the live mode of the USB. There are a few different terminologies used but typically it is Live, Try or Start. On Ubuntu, the option to select is Try Ubuntu.

3 Check disk path

Open the GNOME Launcher and open Terminal.

To check the path of the disk, type in the below command:

sudo fdisk -l | grep nvme

4 Partition of disk

This will reveal the partition of the disk that needs mounting.

5 Mount partitions

Most installs will only have the 2 partitions shown.
Run the below commands to mount them:

Mount Points for:

Star LabTop

mount /dev/nvme0n1p2 /mnt
mount /dev/nvme0n1p1 /mnt/boot

Star Lite

mount /dev/sda2 /mnt 

mount /dev/sda1 /mnt/boot

6 Enable network

Depending on what you need to do in the recovery mode, you may want to enable internet access with:

sudo cp /etc/resolv.conf /mnt/etc/resolv.conf

7 Connecting to installation

From here, we need to chroot into the disk with:

sudo chroot /mnt /bin/bash

8 Connected to installation

This will take you to a terminal window running as root on your SSD.

9 Ready to diagnose

From here we are ready to perform further diagnostics on the installation.

• fsck - Check file system
• GRUB Repair - Update bootloader
• dpkg - Repair broken packages

See further guide on using recovery mode