How to reinstall Grub on the MBR

GRand Unified Bootloader is a Linux-world boot loader, though it can boot any OS you can fit on a drive. Its great for choosing between Windows and Linux on dual boot machines and choosing between different kernels on a given Linux system… you could even use it for booting between different Windows instances.

Anyhow… your machine’s boot sector has croaked.. what to do?!

Load up the distro’s rescue CD and mount the boot partition, say its device is /dev/sda1 ( ‘sda’ means ‘first SCSI device’, the ’1′ means ‘the first partition’)

# mkdir /boot

# mount /dev/sda1 /boot

Now startup grub and get to work:

# grub

grub> root (hd0,0)

grub> find /grub/stage1

grub> setup (hd0)

grub> quit

This basically means: Your root parition is on the first disk’s first partition, and under the /boot directory is the grub information to place into the MBR, and then to actually write it there.

This will make more sense once you do it. Or not.

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This entry was posted by Jason G. on Thursday, February 21st, 2008 at 10:32 am and is filed under Solutions, Website Hosting. You can follow any responses to this entry through the RSS 2.0 feed.

One Response to “How to reinstall Grub on the MBR”

  1. jason says:
    February 21, 2008 at 10:43 am

    Hmmm, I should probably mention that “MBR” means “Master Boot Record”. This is a spot on the very front of your disk which gives the hardware some boostrapping code to run. It usually contains info on how to boot your main OS or how to run an OS selector (like GRUB). If you didn’t already know this, you’ve probably skipped over this blog entry anyway ;)