Re: 回复： Re: [CentOS] Help.I can't start with my new kernel.

[Jim Perrin]

On 8/23/05, cpp fire <fire_cpp at yahoo.com.cn> wrote:
> Oh,sorry,I did not describe it clearly.
> When booting the system,it stops with these words:
> "kernel panic:VFS:Unable to mount root fs on
> unknown-block(0,0)"


First let me say that while this is directed at you, it's not directed
JUST at you. Please do not take it personally.

It seems on the irc channel and in other areas that people are
rebuilding kernels for centos left and right, and when queried as to
why, they falter on an answer.  Your steps used to be correct for
rebuilding a kernel, but distributions have increased dramatically in
complexity to the point that new steps are in order for rebuilding a
kernel for an rpm based distro.

Redhat ( and by proxy centos ) have lilterally hundreds of patches
built into their kernels and because of this it is becoming
increasingly more difficult to use vanilla kernels from kernel.org.
Things like nptl patching etc make running vanilla kernels a
challenge.  Redhat also backports many features of newer kernels to
older versions. For example the RHEL/CentOS 3.x kernel (2.4) contains
many 2.6 enhancements.

While rebuilding kernels for gentoo and the like is fine, for a
package (rpm) based system it can lead to issues if you don't plan for
upgrades, and not just for the kernel. If redhat releases a package
that depends on kernel 1.2.3 (example. no bitching about numbers)
which you installed from source, your rpm database doesn't know that
the kernel is installed, and will tell you it's needed. If you force
it, you'd introduced a conflict into your database which will mean
you'll need to force more and more, which will lead to a near useless
rpm setup.

If you have hardware that's not supported by default or you honestly
feel some burning pull to rebuild your own kernel, you can rebuild the
kernel src.rpm to get the functionality you want by following a guide
Kevin Hobbs of Ohio University wrote.
http://crab-lab.zool.ohiou.edu/kevin/kernel-compilation-tutorial-en/

Or if you absolutely have to rebuild from a stock kernel, you should
be able to use the option "make rpm" so that your database at least
knows it's installed.

</rant>

Again, not personal, and not directed at you alone. 


-- 
Jim Perrin
System Administrator - UIT
Ft Gordon & US Army Signal Center