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So, here's the story of this problem

I have my work laptop dualbooted with Windows7 and Ubuntu 12.04 LTS. I was doing preparations for a tutorial on openGL I wanted to do and I installed some packages, namely, libxmu-dev and libxi-dev. However, one of these changed like 20 packages that were largely the same but with xorg-* instead of xserver-* prefixes. When I rebooted several peripherals didn't work. I mistakenly destroyed the partition that held Ubuntu after making my backups but when I rebooted this message was lying in wait for me.

error: unknown partition  
grub rescue:  

I tried using ls to move around the partitions but no matter what I do I always get the same message.

error: unknown partition

I even tried reinstalling Ubuntu but the install process failed when it reached the grub configuration. What do I do? PS: Sorry If this is a common question, I read around the forums and everyone could read and modify their partitions on first try, not my case however.

share|improve this question
You should be able to reinstall from a live disc, it shouldn't matter how messed up the previous install is, as it will get totally wiped. Is your bootloader somewhere else besides in the ubuntu install? – RhZ Apr 27 '14 at 17:36
During the installation it said that the bootloader was in /dev/mmblck0 but such partition didn't exist. When I tried reinstalling it just said that grub couldn't be found and it was a fatal error, followed by the grub rescue prompt after a reboot. – Francisco Garcia Apr 27 '14 at 17:39
up vote 0 down vote accepted

Francisco mmblck0 is (propably) a SD Card in your laptop. I have similar problem and I was forced to reinstall grub from live CD. Some BIOS and GRUB don't read SD Cards for boot, so this is the problem. I think that solution proposed by RhZ is correct. You should boot from LiveCD login to your machine by chroot and then reinstall GRUB on any bootable partition.

share|improve this answer
When in doubt, reinstalling is always a decent if imperfect way to get things right. – RhZ Apr 28 '14 at 2:33
Surprisingly, this was the problem. After I removed the SD card GRUB complied to the rebuild process and I could get things right again. Thanks. – Francisco Garcia Apr 28 '14 at 20:09

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