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Re: [OCLUG-Tech] linux install with kernel parameters

On Wed, 2005-10-05 at 17:59 -0400, Alex @ Avantel Systems wrote:
> On Wednesday 05 October 2005 17:31, you wrote:
> > On Wed, Oct 05, 2005 at 12:13:47AM -0400, Alex @ Avantel Systems wrote:
> > > [...]
> > > At that point the system complains that no operating system was found.
> > > I'm assuming that the disks are not found because if I use linux rescue,
> > > the disks can't be found and the installer can't find any trace of the
> > > bootloader.
> >
> > "No operating system found" usually means that the BIOS can't find a
> > bootable OS.  GRUB hasn't even entered the picture at this point.  Are
> > you sure your BIOS can boot off this drive?
> 
> Yes - I had it working with RH7.2 and was able to do that with a default 
> install.
> 
> Isn't there a step in between - initrd - which loads the drivers needed to 
> access the disk?  If the correct drivers aren't available the disks can't be 
> seen.  
Simplified you can say that
 Bios scans disks
 Bios decided what disk to boot from
 Bios loads the MBR from the disk
 CPU jumps to the bootstrap loader in the MBR where it finds GRUB
  grub starts it's stuff and boots os

  Since it worked before the scan disk part should be ok
  If the Bios can't find a valid MBR on the disk it normally stops with
"no os found" (and the original IBM PC did jump to ROM BASIC). 
  If the MBR is ok then grub starts but if Grub can't find the menu it
will stop at a prompt, not a "OS not found" message.
  If you are using LILO it will start printing out L I L O and if it
fails it stops, a little like an error code. If it just prints LI (the
most common problem) it can't find the kernel, probably because you
moved the file on the disk.

Exactly what message do you see ? The message may vary depending on the
bios flavour and another possibility is that you somehow use an old MS
disk where the MBR still is intact. If that's the case it will go on to
the MBR but when it fails to find MSDOS.SYS it prints out something like
"no os found".

Assuming it was a problem for grub to write down the MBR in the right
place you can fix that from rescue but exactly how depends a little on
why it failed.

What dos /boot/grub/device.map look like ?
Should at least contain

(hd0) /dev/sda

If so you should be able to do something like

grub --device-map=/boot/grub/device.map --batch <<EOF
install (hd0,0)/boot/grub/stage1 d (hd0) (hd0,0)/boot/grub/stage2 p (hd0,0)/boot/grub/menu.lst
quit
EOF

to write a good MBR.


> 
> The default install couldn't see the disks either - I had to load the modules 
> manually and then the install was able to complete OK.
> 
> Assuming that some specific modules are needed to see the disks, how do I fix 
> that?  I'm assuming I need a different set of drivers in initrd but how do I 
> get there from here?

mkinitrd /boot/initrd-$(uname -r).img $(uname -r)
You may have to add  "--with=the_module_you_loaded" to get it right


> 
> Alex
> ====
> 
> 
> 
> >
> > I don't really know what to suggest though.  One workaround if you have
> > a floppy drive is to always use a boot disk, but since the Fedora disks
> > don't detect your disks automatically, you'll probably need to create
> > one by hand.  If you're familiar with compiling kernels, 'make zdisk' is
> > one way to go.
> >
> > Good luck!
> > Jody

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