GRUB 2 Restore after Windows installation

GRUB 2 Restore after Windows (re)installation

Scenario: Multiple OS in one machine – Linux Grub2 Boot Loader doesn’t start after Windows (re) installation. A selfish Windows OS starts automatically by default. It happens when installing Linux and Windows. This can be easily avoided by installing multiple operating systems in the following order; first Windows then Linux.

Example of existing disk partitions:

/sda1 ntfs  Windows 7 (here, Windows installer set up the Boot flag to active)
/sda2 ext3 Ubuntu ( bootloader’s home partition and the Boot flag has been unset)
/sda3 ext3 home
/sda4 ext3 ….
/sda5 ntfs data/whatever

Requirements:
–    A patient – Computer with multiple OS’s and the bootloader broken by the Windows installer.
–    Ubuntu LiveCD (installation CD) or
–    A light GParted Live CD/USB/HD/PXE – gparted-live-xxx.iso ~121.4 MB (recommended)
–    Mind the OS architecture! Don’t run 32 bit live cd against 64 bit operating system.

Solution: GRUB-2 Boot Loader has been restored by applying the following remedy:

UPDATE

I tried and it did not work against Windows 7 installation! It looks like windows installer don’t care and takes it all, writing its own rubbish into a MBR sector. To fix this OS disaster do the following:

1. Once again, mind the OS architecture; use 32 bit live cd against 32 bit existing OS installation and 64 bit live cd accordingly.
2. Start up either gparted or Ubuntu Live cd (recommend) and issue “fdisk -l” command to learn about existing partitions on the hard disk
3. Identify Linux boot partition and mount the file system into /mnt directory
4. chroot into mounted FS and reinstall grub on the hard drive
5. Update Windows 7 entries in grub2 config file and refresh grub configuration.

Run script:

$sudo fdisk -l

  Device Boot  Start         End      Blocks   Id  System
/dev/sda1          1        1244     9990144   83  Linux
/dev/sda2       1244        1306      492545    5  Extended
/dev/sda3       1244        1306      492544   82  Linux swap / Solaris
/dev/sda4 *	8370	   13995    45190845   69  HPFS/NTFS

#mount existing Linux installation file system (sda1):

$sudo mount /dev/sda1 /mnt
$sudo mount --bind /dev /mnt/dev
$sudo mount --bind /proc /mnt/proc

# chroot into the environment:
$sudo chroot /mnt

#reinstall Grub2 :
$ sudo grub-install /dev/sda
Installation finished. No error reported.

 

Reboot computer, grub menu should start now.

In case that Windows 7 menu entry is missing do the follwoing to add windows 7 to the grub2 menu list:

1. Create Windows config file in /etc/grub.d/ directory
2. Grand execute rights to created file
3. Execute grub update script: sudo update-grub

Script:

# create and fill up 11_Windows configuration file

$ sudo vi /etc/grub.d/11_Windows

# next add the following lines:

#! /bin/sh -e
echo "Adding Windows" >&2
cat << EOF
menuentry "Windows 7" {
set root=(hd0,4)
chainloader +1
}
EOF

 

Save and exit :wq vi editor, this will create a new file.

Mind the fact if the Windows was installed on fourth partition (like in example above) we need to give root=(hd0,4).

GRUB2 recognizes partitions in the following way:

First partition (/dev/sda1): root=(hd0,1)
2nd  partition (/dev/sda2): root=(hd0,2), and so on…

# next grand execute permission to a file:
$ sudo chmod a+x /etc/grub.d/11_Windows

# issue the following command to refresh Grub2 configuration:

$ sudo update-grub

Reboot computer.

Cheers!!