How to reactivate GRUB and change its configuration
Generally, you should refer to the boot loader manual pages for the appropriate procedure. There is also the corresponding Knowledge Base article on the Acronis Web site.
The following is an example of how to reactivate GRUB in case the system disk (volume) is recovered to identical hardware.
- Start Linux or boot from the bootable media, and then press CTRL+ALT+F2.
- Mount the system you are recovering:
mount -t ext3 /dev/sda2 /mnt/system/ # root partition
mount -t ext3 /dev/sda1 /mnt/system/boot/ # boot partition
- Mount the proc and dev file systems to the system you are recovering:
mount -t proc none /mnt/system/proc/
mount -o bind /dev/ /mnt/system/dev/
- Save a copy of the GRUB menu file, by running one of the following commands:
cp /mnt/system/boot/grub/menu.lst /mnt/system/boot/grub/menu.lst.backup
cp /mnt/system/boot/grub/grub.conf /mnt/system/boot/grub/grub.conf.backup
- Edit the /mnt/system/boot/grub/menu.lst file (for Debian, Ubuntu, and SUSE Linux distributions) or the /mnt/system/boot/grub/grub.conf file (for Fedora and Red Hat Enterprise Linux distributions)—for example, as follows:
- In the menu.lst file (respectively grub.conf), find the menu item that corresponds to the system you are recovering. This menu items have the following form:
title Red Hat Enterprise Linux Server (22.214.171.124)
kernel /vmlinuz-126.96.36.199 ro root=/dev/sda2 rhgb quiet
The lines starting with title, root, kernel, and initrd respectively determine:
- The title of the menu item.
- The device on which the Linux kernel is located—typically, this is the boot partition or the root partition, such as root (hd0,0) in this example.
- The path to the kernel on that device and the root partition—in this example, the path is /vmlinuz-188.8.131.52 and the root partition is /dev/sda2. You can specify the root partition by label (such as root=LABEL=/), identifier (in the form root=UUID=some_uuid), or device name (such as root=/dev/sda2).
- The path to the initrd service on that device.
- Edit the file /mnt/system/etc/fstab to correct the names of any devices that have changed as a result of the recovery.
- Start the GRUB shell by running one of the following commands:
chroot /mnt/system/ /sbin/grub
chroot /mnt/system/ /usr/sbin/grub
- Specify the disk on which GRUB is located—typically, the boot or root partition:
- Install GRUB. For example, to install GRUB in the master boot record (MBR) of the first disk, run the following command:
- Exit the GRUB shell:
- Unmount the mounted file systems and then reboot:
- Reconfigure the bootloader by using tools and documentation from the Linux distribution that you use. For example, in Debian and Ubuntu, you may need to edit some commented lines in the /boot/grub/menu.lst file and then run the update-grub script; otherwise, the changes might not take effect.