Ubuntu – How to fix “error: unknown filesystem. grub rescue>

grub2

I get this error:

Error: unknown filesystem.
grub rescue>

I'm not exactly sure what I did. I believe I installed Ubuntu over Windows on my Acer netbook. I then tried to install Linux Mint, but it wouldn't start installing.

I turned the netbook off and back on. Now I get the error.

I have read a lot of other questions like this, but in my case I cannot boot a CD. If I put a Ubuntu CD or a Linux Mint CD into my external CD/DVD drive and change my BIOS to boot the CD-ROM first, it just gives me the same error screen.

Update copied from comment dated 2012-05-26 02:54:29Z

Here are some results from my commands: 

grub rescue>ls (hd0) (hd0,msdos5) (hd0,msdos1) 
grub rescue>ls (hd0,msdos5) unknown filesystem 
grub rescue>ls (hd0,msdos1) unknown filesystem 
grub rescue>ls (hd0) unknown filesystem

Best Answer

The following solved the issue for me, I have Windows 7 & Ubuntu 10.04. After running the following commands I don't need to run these every time and am able to boot both the OS normally:

set root=(hd0,6)
set prefix=(hd0,6)/boot/grub
insmod normal
normal

Now once you boot into Ubuntu, run the following two commands as well:

sudo update-grub
sudo grub-install /dev/sda

Note: /dev/sda is drive where you want your GRUB installed, it can be /dev/sdb or something else, but is usually /dev/sda

Take into consideration that the hd0 could be X (0,1,2..) depending on the order of disks and the 6 could be also different, it could be (hd0,gpt7), for example.

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