initrd stands for initial ram disk. Its absence may prevent your system from
booting --- especially if important pieces of your kernel config (e.g. scsi
driver) are built as modules. It's a chicken and egg thing really. In order
to load a module (which normally reside under /lib/modules) the system must
boot far enough to be able to mount your disk so the *.o module file can be
located. If the module in question is required for mounting the disk in the
first place; however, the module's object file can't very well be loaded from
disk.
Linux gets around this by providing for the creation of a separate compressed
filesystem that can be loaded and uncompressed into RAM early on in the boot
process. This is the initrd-2.4.xxx-img file found in /boot and referenced in
lilo.conf. You can examine its contents by uncompressing and mounting on the
loopback device:
cd /tmp
gzip -c /boot/initrd-2.4.x.img /tmp/initrd-2.4.x.img
mkdir mpt
mount -o loop -t ext2 initrd-2.4.x.img mpt
Following this example, modules files would then be located in /tmp/mpt/lib.
See man mkinitrd for full details, but briefly to make an initrd for your new
kernel all you have to do is:
mkinitrd /boot/initrd-2.4.x.img 2.4.x
*after* you make bzImage; make modules; make modules_install. The second
argument to the command must correspond to a directory tree under
/lib/modules.
I doubt the absence of an initrd is the cause of your problems, however,
since usually the boot process proceeds further and the error is something
like "Failed to mount root filesystem" if initrd is the cause.
Did you run lilo after building your new kernel? Also 2.4.8 is pretty old
now, why not try 2.4.17? The steps I follow to install a new kernel are
(assuming an upgrade from 2.4.16 to 2.4.17)
cp linux-2.4.17.tar.bz2 /usr/src
rm linux # this is the old symbolic link
tar xvjf linux-2.4.17.tar.bz2
mv linux linux-2.4.17
ln -s linux-2.4.17 linux
cd linux
cp ../linux-2.4.16/.config . # this step sets all the config flags that were
# in effect for the working 2.4.16 kernel
make oldconfig # this step confirms previous config and prompts
# for new options
make -j 2 bzImage
make -j 2 modules
make modules_install
cp arch/i386/boot/bzImage /boot/vmlinuz-2.4.17
cp System.map /boot/System.map-2.4.17
mkinitd /boot/initrd-2.4.17.img 2.4.17
Then I edit lilo.conf to add an entry for the new kernel --- being careful to
leave the old kernel's entry in case something goes wrong. The final step is
running lilo:
/sbin/lilo
Without this last step I believe booting will stall at the "uncompressing
linux kernel ..." stage.
HTH,
Marvin Justice
On Thursday 03 January 2002 03:34 am, Vanitha wrote:
> Hi
>
> Check for the correct processor family you have selected during the
> menuconfig selection
>
> What is initrd used for at boot time?
> initrd provides the capability to load a RAM disk by the boot loader
>
> Regards
> Vanitha
>
> ----- Original Message -----
> From: "SATHISH.J" <sathish.j@tatainfotech.com>
> To: "kernelnewbies" <kernelnewbies@nl.linux.org>
> Cc: "linux india programming"
> <linux-india-programmers@lists.sourceforge.net>
> Sent: Thursday, January 03, 2002 4:21 AM
> Subject: [LIP] Could not boot from 2.4.8 kernel
>
> > Hi,
> > I downloaded 2.4.8 kernel from "www.kernel.org" and did the regular
> > kernel make to get the bzImage. Then I tried to boot from the same by
> > altering the lilo.conf. The booting stops with the message "uncompressing
> > linux kernel". I did not add initrd path for this new kernel in
> > lilo.conf. Is it because of that? What is initrd used for at boot time?
> >
> > Thanks in advance,
> >
> > Warm regards,
> > Sathish.J
> > Systems Engineer
> > Tata Infotech Limited
> > 80 Feet Road
> > Indra Nagar
> > Bangalore-560 038.
> >
> >
> > _______________________________________________
> > linux-india-programmers mailing list
> > linux-india-programmers@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/linux-india-programmers
>
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