Ahh … grub. That boot loader. The one that … after interacting with … you wish you didn’t have to.
Just had some fun a few minutes ago on a Lustre upgrade. Some of the grub tools are slightly broken, many are horribly, irretrievably borked.
And they will do bad things to you. To your disk.
Paraphrasing Churchill, grub is the worst bootloader, except for all the rest. I’ll argue that its marginally better than lilo. Grub2 or grub-ng … or whatever, at least as included by Ubuntu in their 10.x series, is a disaster. It went from moderately hard to deal with to pretty much impossible to deal with. The pain I had with Ubuntu 10.x had to do with nouveaux driver, and my inability to disable/blacklist it, so I could install the NVidia driver. Grub2/ng figured prominently in this equation.
Now we ship all JR/DV/siCluster units with a bootable thumb drive … just in case grub throws a hissy fit (as well as solving a bunch of other problems … and the siCluster has much better infrastructure to deal with the vagaries of grub, and borked/blown up installs/updates).
Wanna waste a few hours? Deal with grub.