Reinstall GRUB on Ubuntu 22.04 – Step-by-step

Fixing GRUB

2. 2. Booting Live OS

   First, boot from a Live Ubuntu OS.

   On a PC or Virtual Machine, you may need to Enter BIOS and set the ROM/Drive as the first boot device.

3. 3. Chrooting Ubuntu

   Now to Chroot into Ubuntu OS.

   First, switch to the Admin Prompt:

   sudo su

   Now create the target directory:

   mkdir /mnt/chrootdir

   Then mount the main partition:

   mount /dev/sda1 /mnt/chrootdir

   And the required directories:

   for dir in proc dev sys etc bin sbin var usr lib lib64 tmp; do
     mkdir -p /mnt/chrootdir/$dir && mount --bind /$dir /mnt/chrootdir/$dir;
   done

   Lastly, chroot into the system:

   chroot /mnt/chrootdir

4. 4. Fixing GRUB

   Now to Reinstall GRUB on Ubuntu.

   Run:

   grub-install /dev/sda

   Then update GRUB configuration:

   update-grub

   Exit the chroot environment:

   exit

   Finally, reboot into your restored system:

   reboot

   Thanks to #254491 on Ask Ubuntu.