Comment 11 for bug 437446

There was also a bug report [1] on the console security page of the server guide referencing the GRUB Legacy password protection mechanism.

I submitted patches on that bug report which for karmic and lucid which temporarily removes the section until a sufficient password protection scheme was in place with GRUB 2.

There is a lengthy forum post [2] on working with GRUB password protection, but without the ability to hash passwords as was possible with GRUB legacy, the lightweight security benefits IMO shouldn't be recommended to users just yet.

[1] https://bugs.launchpad.net/ubuntu/+source/ubuntu-docs/+bug/384148
[2] http://ubuntuforums.org/showthread.php?t=1369019