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Re: Problem booting anfter reinstall...

On Fri, May 19, 2006 at 10:36:02AM +0100, Bob wrote:
> Andrew Sackville-West wrote:
> [snipped...]
> >most likely you don't have the right modules loaded. can you insmod
> >them from the busybox shell and then try init 6 (also, I think you
> >only need init 2 in debian, but you can check that by looking at
> >/etc/rc2.d). 
> It was from a fresh netinstall with the Debian installer, I haven't got
> a clue what insmod ism let alone what to do with it...?

sorry. I assumed too much. insmod a command that inserts a module into
the kernel. Sometimes a particular module is not loaded when needed
and has to be manually loaded to get the kernel to recognize a piece
of hardware (see below).

> >Of course, reading back over this, my suggestion assumes you've got
> >modules on a readable disk and I bet you don't...
> You're assuming I know anything about modules...

A module is essentially a piece of the kernel that (typically) drives
a piece of hardware. Sometimes they work alone, sometimes theywork in
concert with other modules to get something to work. Linux uses one of
two methods to control hardware: you can either compile the code for
the particular piece of hardware directly into the kernel to ensure
that it is available at boot time, or you can compile it into a module
that is inserted into the kernel as needed. 

Usually what happens is the kernel is compiled with a fairly minimal
amount of hardware drivers included... just enough to get the thing up
and running, then other modules are inserted to drive other
hardware. These modules (someone will correct me if I'm wrong here,
but I think I've got the gist of it) that are needed to get a kernel
up far enough to read your disks etc are placed in what is called an
initial ram-disk or initrd. This initrd is loaded into memory early
in the boot to give the kernel access to any hardware that is not
already included in the kernel. (I'm way past my knowledge level
here... someone help). WHat I think has happened in your situation is
that the modules needed to see your hard-disks is neither in your
kernel nor accessible from the initrd. So, when the kernel boots, it
can't see your harddisks and consquently can't run, and drops you into
the busybox shell so that you can, theoretically, fix it.

> >you could boot from a live-cd (knoppix) and chroot into your system
> >and rebuild the initrd to include the proper modules in the initrd. I
> >think its dpkg-reconfigure yaird or initrd-yaird. Others will know
> >this.
> I think I might just down load a DVD image and try installing from
> that...

You're certainly welcome to do that, and no-one will fault you for
it. There is an opportunity here, though, if you are inclined, to
learn a little of what is going on under the hood. If you have a
bootable cd (like a live-cd such as knoppix), or if the net-installer
has the right tools (I don't know) you can fix it with out going
through the whole reinstall process. The idea is to get a kernel
booted with one of these methods, and then rebuild the initrd so that
it has what you need in it to get the system to boot properly. There
are others here who are VASTLY more qualified to help you with
this. Hopefully someone will chime in. (hear me begging here? :)

So the procedure *I* would follow, is get that thing booted with one
of the methods I mentioned above. run lsmod to see which modules you
are using to see those harddrives. Then chroot (change root) into the
root directory of your current installation. 

mount /dev/sda1 /mnt (this assumes you're root is at /dev/sda1 and is
seen by the current system)


chroot /mnt


dpkg-reconfigure yaird (might be initrd-yaird or initrd)

this command will rebuild the initial ramdisk. hopefully, it will
pickup what you need and put it in that initrd and you're good to go. 

I apologise for not knowing more about this. Reinstalling will likely
be MUCH easier if this is all new to you.

hope this helps


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