I'm using Slackware 12.2,upgrading from original kernel to recent one,which is 2.6.29.4.

I follow all the steps in here to upgrade and recompile the kernel.

But when I booted the new kerne,the following error popped up;

VFS:Cannot open root device "308" or unknown block (3,8)
Please append and correct "root=" boot option;here are the available partitions;

Kernel panic.not syncing:VFS:Unable to mount root fs on unknown block (3.8)

Do you know why the error and how to solve this?Thank you and sorry for my bad English.

I would check your boot managers configuration file if its grub then it would be menu.lst listed normally in /boot/grub/ the root= line is what its complaining about this needs to be the harddisk that you have your / partition


Also its possible you forgot to include in the kernel configuration drivers for your hard drive controllers or file system.

I made the same mistake once. I configured ext3 as a module when it needs to be built in to the kernel.

as mlangdn said, when you recompile your kernel make sure your FS is listed as a built in (<y>) not as a module. If it is built as a module you will need to make an initrd.gz file that will tell the kernel what to load.

I recompiled the kernel again,and it shows sign of improvement although I failed to boot them;

VFS:Cannot open root device "308" or unknown block (3,8)
Please append and correct "root=" boot option;here are the available partitions;

sda1
sda2
sda8(My root partition)

Kernel panic.not syncing:VFS:Unable to mount root fs on unknown block (3.8)

These were the steps I did;

1.Edited my lilo.conf,changed root=/dev/hda8 to root=/dev/sda8.
2.Ran lilo,but there were some error that states root=/dev/sda8 is not a valid specification.
3.Rebooted and I found that the root's MBR isn't renewed.

What I need to do now??

This is an excellent kernel compile guide:

Building a Linux Kernel from source

Edit lilo.conf again.

root=/dev/sda8 should be:

root = /dev/sda8

Then re-run lilo and see if it gives an error.

Try to revert it again to root = /dev/hda8 and ran LILO
make sure it worked and then when you boot, press tab or escape to get the LILO prompt and then select the correct kernel and add
this will overwrite the root partition should be used to boot the kernel.

The problem with your LILO is because the current kernel you are running doesn't recognize your /dev/sda8, so it complaints. The solution is to use the old value and overwrite it during boot time using above's way

Finally,I get to run my shiny new kernel and typing my post using the new kernel.

1.I edited the root = /dev/sda8 to root = /dev/root
2.I finally booted my new kernel,but of course it's not the end of my problems.I forgot to build some important modules,and I rebuild them and I get to run new kernel.

To be frank,this is my first time compiling a new kernel.So far I did not notice increase in performance despite having the kernel shrinked slightly from 4.3 MB to 3.5 MB.But this should be a good experience for me indeed.

You might not get so much of a boost in speed and such.. but you get better support for more things. But using a newer kernel, and a custom one is something that I see as a good thing anyways.