Stuck on GRUB Command Line

I am running Natty Alpha 3. I used Update Manager to install something (not sure what it was), then I restarted, but instead of listing all the kernels, it gave me a command line. I don't know what happened and how to use it. Help!

May I suggest you to recover your grub installation with a live cd?
I could recover grub many times by following these instructions at: https://wiki.ubuntu.com/Grub2#Recover

"METHOD 3 - CHROOT

This method of installation uses the chroot command to gain access to the broken system's files. Once the chroot command is issued, the LiveCD treats the broken system's / as its own. Commands run in a chroot environment will affect the broken systems filesystems and not those of the LiveCD.

1) Boot to the LiveCD Desktop (Ubuntu 9.10 or later). Please note that the Live CD must be the same as the system you are fixing - either 32-bit or 64-bit (if not then the chroot will fail).

2) Open a terminal - Applications, Accessories, Terminal. 3) Determine your normal system partition - (the switch is a lowercase "L")

sudo fdisk -l

If you aren't sure, run

df -Th 

Substitute the correct partition: sda1, sdb5, etc.

sudo mount /dev/sdXX /mnt  

sudo mount /dev/sdYY /mnt/boot 

sudo mount --bind /dev  /mnt/dev
sudo mount --bind /dev/pts  /mnt/dev/pts
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys  /mnt/sys 

sudo chroot /mnt 

8) If there is no /boot/grub/grub.cfg or it's not correct, create one using

update-grub 

9) Reinstall GRUB 2:

Substitute the correct device - sda, sdb, etc.

Do not specify a partition number (e.g. do not specify sda5, instead it could be sda)

grub-install /dev/sdX 

10) Verify the install (use the correct device, for example sda. Do not specify a partition):

sudo grub-install --recheck /dev/sdX 

sudo umount /mnt/dev/pts
sudo umount /mnt/dev
sudo umount /mnt/proc
sudo umount /mnt/sys 

13) If you mounted a separate /boot partition:

sudo umount /mnt/boot 

14) Unmount the LiveCD's /usr directory:

sudo umount /mnt/usr 

15) Unmount last device:

sudo umount /mnt 

16) Reboot.

sudo reboot 

It happened to me too, on a regular upgrade. Thankfully I was working on the dev system, determining the stability of the upgrade before pushing it to production.

The answer from "steabert" is not helpful at all. That's the answer for people who run Windows. Early releases are for finding bugs, and Cg2916 found one.

I recovered by using the grub console to continue booting, then reinstalled grub after I was able to log in.

set root (hd0,1)
linux /vmlinuz root=/dev/sda
initrd /initrd.img
boot

Lots of fun boot stuff happens

sudo grub-install /dev/sda

Of course, you'll need to adjust for correct partition numbers and device names, but it's fairly painless after you get over the initial pain.

Now, how do I do this on a virtual machine in a remote location where I only have SSH access...