error: no such partition, grub rescue

If we come across the error in grub

Error: No such partition grub rescue>

It indicates that the partition on which grub was installed is no longer accessible. Which could be because it has been formatted or disconnected etc. There are a few ways of getting out of this situation.

If there is another partition on which we have a working OS we can boot into that OS using the following steps

grub resuce> ls (hd0) (hd0,1) (hd0,2) (hd0,4)

The command in ls lists the partitions that grub is able to access.In the above example there are 3 partitions 1,2 and 4. If we know which among these has the working OS installed in it we can use the following set of commands to boot into it. Assume that (hd0,2) has the working OS.

grub rescue> set prefix=(hd0,2)/boot/grub grub resuce> set root=hd0,1 grub resuce> insmod normal grub rescue> normal

Once we have booted into the working OS, if the another OS happens to be linux we can reinstall grub so that on next reboot the grub does not hang. To reinstall we need to find the partition on which grub needs to be installed which can be done using the command

$ sudo fdisk -l Disk /dev/sda: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: Device Boot Start End Blocks Id System /dev/sda1 2048 718847 358400 de Dell Utility /dev/sda2 718848 7010303 3145728 c W95 FAT32 (LBA) /dev/sda3 * 7010304 445635303 219312500 83 Linux

The above output indicates that the hard disk on which operating system is installed is /dev/sda thus we can install grub using the command

$ sudo grub-install /dev/sda

If we do not have a working OS in any other partition then we need reinstall the grub using a live cd or a dvd or a live usb. Insert the live cd/dvd and boot the system. Once the live cd boots open a terminal and run the command

$ sudo fdisk -l Disk /dev/sda: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: Device Boot Start End Blocks Id System /dev/sda1 2048 718847 358400 de Dell Utility /dev/sda2 718848 7010303 3145728 c W95 FAT32 (LBA) /dev/sda3 * 7010304 445635303 219312500 83 Linux

From the output look at the last column and the try to find the parition on which the os is installed. For example in the above case it is /dev/sda3.

Now execute the commands

$ sudo mount /dev/sda3 /mnt $ sudo mount /dev/sda3 /mnt/boot $ sudo mount --bind /dev /mnt/dev/ $ sudo chroot /mnt $ grub-install /dev/sda $ sudo reboot

The error should no longer appear.

Useful Links

http://www.gnu.org/software/grub/manual/html_node/GRUB-only-offers-a-rescue-shell.html#GRUB-only-offers-a-rescue-shell
http://www.gnu.org/software/grub/manual/html_node/Installing-GRUB-using-grub_002dinstall.html
http://howtoubuntu.org/how-to-repair-restore-reinstall-grub-2-with-a-ubuntu-live-cd#.UmgPBuHWSBs

For windows users

http://www.sevenforums.com/tutorials/20864-mbr-restore-windows-7-master-boot-record.html