Ubuntu – Recovering GRUB after installing Windows 7?


Possible Duplicate:
How can I repair GRUB? (How to get Ubuntu back after installing Windows?)

I installed Windows 7 after it crashed, and now I am unable to boot Ubuntu. Ubuntu partitions are still there. I tried using Boot-Repair, but it didn't work!

Best Answer

You can re-install grub in the Master Boot Record using the LiveCD for you distribution version,

It goes like this:

  • Boot from LiveCD ⋯ please try to use a LiveCD that has the same version of Grub2 as the installed version

  • Mount the root of the installed Ubuntu at /mnt

  • Change root

  • Update grub

  • Install grub

  • Reboot

The above steps are from near the bottom of the Ubuntu Community Documentation of Grub2

After booting from the liveCD ( select "Try Ubuntu" on the opening screen)

Then start up a terminal (dash, type-in terminal, … )…

  • It may be easier to open this web page while running LiveCD. Firefox should allow you to do this.

Type in the terminal sudo fdisk -l - and enter your password if asked. That's a lower case L. Find the installed Ubuntu partitions, (from mine with other disks snipped ― here):

me@mycomputer:~$sudo fdisk -l
Disk /dev/sde: 300.1 GB, 300089646592 bytes
255 heads, 63 sectors/track, 36483 cylinders, total 586112591 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xc3f5ebeb

Device    Boot      Start         End      Blocks   Id  System
/dev/sde2       138464296   586110975   223823340    5  Extended
/dev/sde3   *        2048   138463231    69230592   83  Linux
/dev/sde5       138464298   313460279    87497991    7  HPFS/NTFS/exFAT
/dev/sde6       313460736   317650943     2095104   82  Linux swap / Solaris
/dev/sde7       317652992   581922815   132134912   83  Linux
/dev/sde8       581924864   586110975     2093056   82  Linux swap / Solaris

Partition table entries are not in disk order

Find your Linux installation (Id=83, System=Linux0 then type in

sudo mount /dev/sde3 /mnt

but use your partition instead of /dev/sde3(my root partition is sde3, sde7 is my home partition).

This is assuming that you do not have a separate /boot partition. If you do, you will need to also mount it by typing

sudo mount /dev/sd·· /mnt/boot

where sd·· is the partition where you installed the separate boot directory.

ls /mnt - just checking to see if I got it right:

me@mycomputer:~$ sudo mount /dev/sde3 /mnt
me@mycomputer:~$ ls /mnt
bin   cdrom  etc   initrd.img      lib         media  opt   root  sbin     srv  tmp  var      vmlinuz.old
boot  dev    home  initrd.img.old  lost+found  mnt    proc  run   selinux  sys  usr  vmlinuz

You should test to see if the boot directory is properly installed. Type in ls /mnt/boot and if it is empty, the boot directory is not installed. It should look something like this:

me@mycomputer:~$ ls /boot
abi-2.6.35-30-generic     initrd.img-2.6.35-30-generic  System.map-2.6.35-31-generic
abi-2.6.35-31-generic     initrd.img-2.6.35-31-generic  vmcoreinfo-2.6.35-30-generic
config-2.6.35-30-generic  memtest86+.bin                vmcoreinfo-2.6.35-31-generic
config-2.6.35-31-generic  memtest86+_multiboot.bin      vmlinuz-2.6.35-30-generic
grub                      System.map-2.6.35-30-generic  vmlinuz-2.6.35-31-generic


for i in /dev /dev/pts /proc /sys; do sudo mount -B $i /mnt$i; done
sudo chroot /mnt #change the root
sudo update-grub # now update grub


me@mycomputer:~$ sudo for i in /dev /dev/pts /proc /sys; do sudo mount -B $i /mnt$i; done
me@mycomputer:~$ sudo chroot /mnt
me@mycomputer:~$ sudo update-grub
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-3.0.0-13-generic
Found initrd image: /boot/initrd.img-3.0.0-13-generic
Found linux image: /boot/vmlinuz-3.0.0-12-generic
Found initrd image: /boot/initrd.img-3.0.0-12-generic
Found memtest86+ image: /boot/memtest86+.bin
Found Microsoft Windows XP Professional on /dev/sdc1

Now to re-install grub in the MBR. You will need to know which disk your system boots from, and find it in the fdisk -l listing you have already done. Then type in sudo grub-install /dev/sd replacing sd· with the disk you will boot from.

me@mycomputer:~$ sudo grub-install /dev/sd·

Then type in Crtl-D to exit chroot.

Then type in sudo for i in /sys /proc /dev/pts /dev; do sudo umount /mnt$i; done - as one line

me@mycomputer:~$ sudo for i in /sys /proc /dev/pts /dev; do sudo umount /mnt$i; done

If you mounted a separate /boot partition, type in sudo umount /mnt/boot

me@mycomputer:~$ sudo umount /mnt/boot

Then type in sudo umount /mnt

me@mycomputer:~$ sudo umount /mnt

Then type in sudo reboot to restart he system (remember to remove the LiveCD).

me@mycomputer:~$ sudo reboot

Hopefully, grub will be installed.

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