Ask Ubuntu is a question and answer site for Ubuntu users and developers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

The power supply went out on our machine. We replaced the power supply.

Now when we boot up, all we get is a blank screen with a blinking cursor.

So we hold shift during boot up, and this error is displayed:

error: hd0 cannot get C/H/S values.
grub rescue>

I typed ls and I see (hd0) and (fd0).

Is this installation screwed? Do we need to re-install? If so, can we use an Ubuntu Live disc to retrieve some of our files from the HDD's?

We are using: Ubuntu 12.04 LTS (32bit)

share|improve this question

You can use a Ubuntu Live-CD to access your files and you can also use it to repair your system:

  1. Boot from the live cd
  2. Install lilo (sudo apt-get install lilo)
  3. If it is installed run: sudo lilo -M /dev/XXX mbr where XXX is your harddrive. In most cases XXX is sda. This installs a new master boot record (mbr) into the specified device. For details look at the manpage of lilo. When you enter the command you probably will see some warnings. You can safely ignore them. Several years ago lilo was the default boot manager and the warnings are related to that.

Now your system should boot without any problems.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.