When GRUB is corrupted, your PC can't boot into Linux. Here's what I did:
- First, grab a copy of the latest Ubuntu
LiveCD and boot it. In my case, I made a startup USB thumb drive and booted with it. It boots a bit faster.
$ sudo fdisk -l
- Now, you need to remember which device
listed is your linux distribution, for reference, /dev/sda1 will be
used. Now we need to mount the filesystem to /mnt
$ sudo mount /dev/sda1 /mnt
- If you have /boot
on a separate partition, that need to be mounted as well. For
reference, /dev/sda2 will be used.
$ sudo mount /dev/sda2 /mnt/boot Make sure you don't mix these
up, pay attention to the output of FDISK
- Now
mount the rest of your devices and some other things needed in the
chroot
$ sudo mount --bind /dev /mnt/dev
$ sudo mount --bind /proc /mnt/proc
$ sudo mount --bind /sys /mnt/sys
- Now chroot into
your system
$ sudo chroot /mnt
You should be chroot'd into your system as root, you can
now run commands as root, without the need for sudo.
$ nano /etc/default/grub
$ update-grub
$ grub-install /dev/sda
$ grub-install --recheck /dev/sda
- Press Ctrl+D to exit out
of the chroot.
- Once
you exit back to your regular console, undo all the mounting, first the
/dev and others
$ sudo umount /mnt/dev
$ sudo umount /mnt/sys
$ sudo umount /mnt/proc
- Now you can
unmount the root system. (But if you have a separate boot partition
which you mounted earlier, you have to unmount this first, or you will
get a "device busy" error message.)
$ sudo umount /mnt
- And you should be free to restart your
system right into GRUB 2 and then into your system installation.
If you
had alternate OS entries, update-grub might say "Cannot find
list of partitions!". Ignore it and continue - once you can boot into
your linux installation, do so and then rerun update-grub and grub-install /dev/sda
as root. Reference: - https://wiki.ubuntu.com/Grub2
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