Unfortunately, maintaining a multi-boot configuration like this can be a pain, especially if you later install an operating system which overwrites the GRUB boot loader you had in place (such as a version of Windows). If your boot loader is overwritten, you could be left with no choice but to boot the most recently installed OS.
In this tutorial, I will show you how to restore an overwritten copy of the GRUB boot loader by using a Linux live CD. In this example, my master GRUB installation is on a Fedora 15 installation, and I’m using a Fedora 15 Live CD to boot the system.
Start the Live CD up as normal. Don’t choose to install the OS if prompted, you want to come to a full live desktop to run the specific commands we need.
1. Identify your Partitions
Open a Terminal program and use the following command:
[alexm@localhost ~]$ su
[root@localhost /]# 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 / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x4b474b47
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 206847 102400 7 HPFS/NTFS/exFAT
/dev/sda2 206848 91394047 45593600 7 HPFS/NTFS/exFAT
/dev/sda3 91394048 402077695 155341824 83 Linux
/dev/sda4 402077696 976771071 287346688 f W95 Ext'd (LBA)
/dev/sda5 402079744 976771071 287345664 7 HPFS/NTFS/exFAT
[root@localhost /]#
If you can work out where your Linux is from this, note down the information under ‘Device’.
In this tutorial, Fedora 15 is installed in /dev/sda3
2. Run grub-install
[root@localhost ]# sudo -i
[root@localhost ~]# mount /dev/sda3 /mnt
[root@localhost ~]# grub-install --root-directory=/mnt/ /dev/sda
Installation finished. No error reported.
This is the contents of the device map /mnt//boot/grub/device.map.
Check if this is correct or not. If any of the lines is incorrect,
fix it and re-run the script `grub-install'.
# this device map was generated by anaconda
(hd0) /dev/sda
[root@localhost mnt]#
