Kernel Panic: VFS: Unable to mount root fs on unknown-block

Igor007 · 08-13-2005, 06:00 AM

I have installed Fedora Core 3 and installed all features. I have not found sources of kernel. I have downloaded the latest stable sources of kernel from www.kernel.org .
I have compiled it.

make mrproper
make xconfig
make dep
Command “make dep” answered that this is not necessary.
make clean
make bzImage
make modules
make modules install

I have copied bzImage to /boot/vmlinuz
I have made chages in grub.conf
When I restarted I have got the following Error:

kernel panic - not syncing : VFS: unable to mount root FS on unknown-block (0, 0)

What I have noticed is that no initrd.img file was generated in compilation folder
I think that problem is in it.

I am not sure system.map is proper
What is for system.map and how it should be created or when it is created

EXTRAVERSION is not added to for the image and to any files

What do you think guys. Any body faced with this situation.

What for is initrd.img?

What for is bootspalsh. Can initrd.img be replace with bootsplash somehow?

Why Command “make dep” answered that this is not necessary?

Thanks in advance

Bruce Hill · 08-13-2005, 06:34 AM

I assume by the latest stable kernel you mean 2.6.12.4. You can find instructions for building a kernel in the ./linux-2.6.12.4/README file that were written by Linus Torvalds. The only steps necessary for 2.6.x.x kernels are:
$ make
$ make modules
# make modules_install

Here is a good guide for building 2.6.x.x kernels by Jesper Juhl. You do not need to symlink the System.map file as he says at the end of his guide, but everything else you should do.

You are probably getting the kernel panic because you don't have support for your / filesystem built into your kernel. When you configured the kernel you had the choice of Y (built in) or M (module). If you chose M for you / filesystem, the kernel will not boot, because the module is not loaded before you access that partition.

If you choose M for the filesystem of your / partition, then you must have an initrd.img. I will post what Slackware's Pat Volkerding says about an initrd.img:

Quote:

Slackware initrd mini HOWTO
by Patrick Volkerding
Sun Jun 20 01:38:41 PDT 2004

This document describes how to create and install an initrd, which may be
required to use the 2.6 kernel. Also see "man mkinitrd".

1. What is an initrd?
2. Why to I need an initrd?
3. How do I build the initrd?
4. Now that I've built an initrd, how do I use it?

1. What is an initrd?

Initrd stands for "initial ramdisk". An initial ramdisk is a very small
Linux filesystem that is loaded into RAM and mounted as the kernel boots,
and before the main root filesystem is mounted.

2. Why do I need an initrd?

The usual reason to use an initrd is because you need to load kernel
modules before mounting the root partition. Usually these modules are
required to support the filesystem used by the root partition (ext3,
reiserfs, xfs), or perhaps the controller that the hard drive is attached
to (SCSI, RAID, etc). Essentially, there are so many different options
available in modern Linux kernels that it isn't practical to try to ship
many different kernels to try to cover everyone's needs. It's a lot more
flexible to ship a generic kernel and a set of kernel modules for it. The
generic 2.6 kernel in Slackware supports the ext2 filesystem (which is
used by the initrd), and also supports most IDE controllers (much like the
old bare.i kernel). So, if you have an IDE based system that uses the
ext2 filesystem, then you will not need to use an initrd to boot.
Otherwise, read on.

Bootsplash is just an image that is displayed rather than the standard LiLO or GrUB splash screen. It has nothing to do with an initrd.img

Please read the README file and if you have more questions, post back.

keefaz · 08-13-2005, 06:37 AM

I will just point out that make clean destroyed your .config file generated
with make xconfig, so basically just don't run make clean after you configure
the kernel.

Your error message shows that the kernel wasn't able to mount the root
partition, maybe because the root partition filesystem or the hard drive
controler driver weren't compiled

[edit]
as chinaman said

vimico · 08-14-2005, 07:54 PM

The simplest solution in your case seems to be to make make the driver for the file system you use for the root file system (ext2, or ext3, or ReiserFS, ...) a "built-in" kernel module.

You also need the driver to access your hard drive controller (ATA, or SCSI...) as a "built-in" module.

The second option - putting "external" modules into an initrd, so that they can be accessed during boot time - is more complicated.