Interesting recovery frustrations

[Avi Greenbury]

MR ZenWiz wrote:
> 
> 1. First and foremost, why do we have such an unbelievably arcane
> method of influencing or controlling the boot process?  There isn't a
> single facility to display what grub will do or what its settings are
> other than to read the fairly complex set of files used to generate
> the grub.cfg file.  Even something as simple as a
> grub-show-me-what-the-heck-yo're-going-to-do-on-the-next-boot is not
> available.

I remember complaining of the lack of this with Grub 1. Grub 2 seems
uneccesarily incomprehensible compared to the now-quite-simple-looking
Grub1.
My minimal exposure to Grub2 scared me back to ext3 since I break grub
way too often to get my head round what's going on there.

> 2. Is there a better way to recover form a situation like this (OS
> overwritten intentionally after being backed up, restoring the backup
> and not having it work)?  Obviously, not using the same root and boot
> partition would have been a better choice, but frankly I wasn't
> expecting this much of a headache getting back.

I do this quite frequently with Grub1, and I'm surprised it sounds so
hard on Grub2. The biggie, though, is that you do need to know what
your / is on, and where you want the boot loader installed.
Generally, though, boot through grub's prompt into the OS you want to
have work again, then grub-install works for me. 
It probably doesn't help us here that we don't have any error messages,
just an "it went wrong" ;)
 
> Comments?  Thoughts?  Please skip any "don't do that" or "stick with

My first would be to try to get comfortable with the Grub command line
and Linux kernel arguments. 
It's not that difficult to boot from the grub prompt when you know how,
and it does come in handy if you're doing this sort of thing at all
frequently. It's a _lot_ simpler than repeated reboots into the wrong
OS and attempted grub-installs - if the system's up on the / that
you're aiming for, a grub-install's much more likely to do what you
want.

It does only take about four commands to boot a linux:

root (hd0,0)
kernel /boot/vmlinuz-2.6.32-2 root=/dev/sda1
initrd /boot/initrd.img-2.6.32-2
boot

The first line's specified a device from which to boot [ (first disk,
first partition) ], the second specifies a kernel on that device and
tells it where to look to find /, the third specifies an initrd image,
and the fourth tells it to boot.

And you don't need to remember those version numbers - grub
tab-completes both the commands and the files. The common thing is to
forget to specify a root to the kernel.

-- 
Avi