Recently the service provider link suddenly broke,while I was updating. Then suddenly while I was trying to boot, i could not. The message on my screen was grub recover missing, and I had no option but the grub recover command line. I really did not know what to do. So I installed an earlier version of ubuntu 10.04. It started to boot normally. Now my system is back to 12.04 the version i was working with. How does one handle problems like this?
When the Service Provider link broke, your computer was probably updating GRUB. If the GRUB updating process is interrupted, then GRUB will be broken because of the unsuccessful update.
What happened was that your GRUB is broken, so it redirected you to the GRUB command line, waiting for you to type stuff into it.
After that you installed Ubuntu 10.04. Ubuntu will automatically install GRUB onto your computer, so your GRUB is recovered. When the installation had finished, GRUB then automatically detects any Operating Systems on your computer. It eventually found your old copy of Ubuntu 12.04 on your computer and allows you to boot into it.
GRUB is awesome.