[Sussex] grub problem - post kernel upgrade

[Steve Williams]

On Mon, 2005-11-14 at 20:24 +0000, John D. wrote:
> Steve Williams wrote:
> 
> > John D. wrote:
> >
> >> Hi list,
> >>
> >> During my regular "emerge -uD world", I noticed that there was a new 
> >> kernel version.
> >>
> >> So as usual, I ran genkernel to compile it. When it came to reboot 
> >> the damn system would only drop me into a grub prompt (grub>).
> >>
> >> The only thing that I could find was telling me to do
> >> "grub> root (hd0,0)"
> >> and
> >> "grub> setup (hd0)"
> >>
> >> I don't understand what either of those commands did.
> >>
> >> Amongst my pile of junk I located a kanotix live CD (knoppix 
> >> derivative). Booted that and can see that there is a grub.conf and a 
> >> grub.conf.bak in the /boot partition. The problem seems to be that I 
> >> can't just copy the old version from the .bak to the main grub.conf 
> >> because when I try that I just get told that the main system is only 
> >> available in read-only - I've done some searching for ideas, but both 
> >> the main knoppix page and one from IBM's site that says about 
> >> rescuing with knoppix tell me to mount and the chroot - but I can't 
> >> chroot to get into the main system.
> >>
> >> Obviously, it'd be better if I could just copy the .bak to the main 
> >> grub.conf (which appears to be empty), but I'd write it long hand and 
> >> enter the info if I can just get into the system or see the grub.conf 
> >> file via the grub> prompt.
> >>
> >> Does anyone know how I can get round this please??
> >
> >
> >
> > OK. What kernel were you running, and what kernel post emerge?
> >
> > Steve W.
> 
> Just for info Steve, I was going from the the 2.6.13-gentoo-r5 to the 
> 2.6.14-gentoo-r2 kernels respectively. I also recall a recent upgrade of 
> genkernel itself. So I couldn't work out what or why things had gone 
> pear shaped.
> 
>  From what I remember of a days "meddling", it appears that when I ran 
> genkernel, it compiled OK, but rather than adding the entry to my 
> grub.conf, it seems to have left it as an empty file, but at the same 
> time creating a .bak version of the old grub.conf and also one called 
> grub.conf~ and while I understand the principle of making the .bak 
> version, the one that ended in a tilde made great whooshing noises as it 
> went over my head.
> 
> It also seems that something occurred elsewhere, because it was 
> suggested at LQ that I look for this line
> 
> lrwxrwxrwx  1 root root       1 Aug 20 01:26 boot -> .
> 
> Which wasn't there (checked using ls -l /boot). I was trying absolutely 
> anything that even vaguely held the promise of a solution - but I 
> noticed the problem was sorted after I did the /sbin/grub-install 
> /dev/hda command for either the 4th or 5th time today (I was trial 
> rebooting in between attempts). I just so happened that that was the 
> last thing that I did before "it" appeared to be sorted out.
> 
> So I'm a happy bunny again, now that I've got the gentoo back up and 
> running.
> 
> I didn't manage to suss out why Kanotix wouldn't let me do the chroot 
> command to be able to make any repairs with it (knoppix based live CD - 
> just a little more polished). Plus I was unsure about using the gentoo 
> install cd to get too that stage, because from memory theres a lot of 
> stuff normally done before you get to the chroot stage - and I'm not 
> sure which bits I would need and which bits I would be able to leave out 
> to get to the stage where I can do the chroot and then have tried to 
> mend the /boot stuff and the grub.conf.
> 
> In fact, I'm still trying to work out what I need to input, when I use 
> genkernel i.e. so that not only does it compile the kernel and add the 
> entry to the grub.conf, but so it also rebuilds the external modules 
> (nvidia driver and alsa) rather than having to remember how to do that 
> post compile of the new kernel. I did install the modules-rebuild 
> facility but haven't sussed out how that works.

You would save yourself a lot of trouble if you learnt to configure your
kernel manually.

cd /usr/src/linux
make xconfig/menuconfig/config
make && make modules_install
cp arch/i386/boot/bzImage /boot/vmlinuz (or whatever)
cp System.map /boot/System.map

nano -w /etc/grub/grub.conf

edit grub.conf to take advantage of your new kernel.

Steve W.



> 
> regards
> 
> John D.
> 
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