The situation couldn't be much simpler. Yesterday I downloaded the alternate installer for 12.04 and installed it as the only system on the only hard drive in a system, selecting guided partitioning using the enitre disk. The entire installation went flawlessly, and the network was available the enitre time for package retrieval. The system then rebooted perfectly, and I proceeded to allow the update manager, which launched spontaneously, to download and install all new updates, bringing the entire system up to date as of about an hour ago. After installing openssh-server manually, I rebooted the system as update-manager requested - to find myself stuck at the grub prompt. I was surprised by this given that the previous - and only - boot of this system had been successful.
The screen says:
GNU GRUB version 1.99-21ubuntu3
Minimal BASH-like line editing is supported. For the first word, TAB lists possible command completions. Anywhere else TAB lists possible device or file completions.
What I have tried so far is to rerun grub-install according to the directions here. Although the 12.04 live CD fails to boot completely, apparently having a problem with the video driver, which is why I used the alternate installer, I was able to reach the command line through Ctrl-Alt-F1. The "sudo fdisk -l" command shows the following partitions:
Disk: /dev/sda: 300.1 GB, 300069052416 bytes
255 heads, 63 sectors/track, 63481 cylinders, total 586072368 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical); 512 bytes / 512 bytes
I/O size (minimum/optimal); 512 bytes / 512 bytes
Disk identifier: 0x00019e7e
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 584509439 292253696 83 Linux
/dev/sda2 584511486 586072063 780289 5 Extended
/dev/sda5 584511488 586072063 780289 82 Linux swap / Solaris
As I said, the commands:
sudo mkdir /media/sda1
sudo mount /dev/sda1 /media/sda1
sudo grub-install --root-directory=/media/sda1 /dev/sda
completed successfully, but had no effect on the failure to boot.
I assume that when I updated my system that something was wrong with the latest kernel put into the repository and that it needs to be replaced, so I hope that my other 12.04 system will not be affected. Meanwhile, I could use suggections for how to boot and restore my new, bricked system.