grub rescue

if get error as follows at the of boot:

No Such partition..

grub rescue>

or unknown file system

grub rescue>

follow the following steps:

1. run ls command

2. you will get list of partitions

3. apply ls comman on each

4. ls (hd0)

 you will get 'not found' or unknown file system message

apply ls on next partition eg

ls (hd0,msdos8)

again  you will get 'not found' or unknown file system message

apply ls on next partition eg
ls (hd0,msdos7)
now suppose here you gets some list of files and folder. THis indicates that your ubuntu/linux is installed here

now apply ls (hd0.msdos7)/boot/grub

you should get list of mod files

5. Now use following commands

set root=(hd0,msdos7)

set prefix=(hd0,msdos7)/boot/grub

insmod normal

normal

Your system to start...

6. Once you started the system in Linux

   Re-install the grub

    sudo grub-install /dev/sda

do not put partition number like sda1 or sda2

Update the grub:
 sudo update-grub