(Solved) Problem compile kernel on Ubuntu and using on Debian

(Solved) Problem compile kernel on Ubuntu and using on Debian

[Jesper Dangaard Brouer]

Hi Google,

I had a problem compile kernel 2.6.31.3 on an Ubuntu 9.04 server (CPU
core i7) and using it on a Debian 5.0.3 lenny (CPU Atom 330).  Both
systems using the 64-bit version of the OS'es.  And kernel compiled
for x86_64.

Problems seen:
 "Waiting for root file system..."

If you get past this one, by compiling enough modules into the kernel,
BUT then a lot of modules does not seem to be loaded (modprobe).

Solution:

The solution seems to be related to the modules.dep files generated on
the Ubuntu system and copied to the debian system.

Run the following commands on the debian system:

 depmod -a              2.6.31.3-ubuntu-compiled
 update-initramfs -u -k 2.6.31.3-ubuntu-compiled
 update-grub2

Which means:
 1. update the modules.dep files
 2. recreate the initrd.img
 3. update the grub config

Q: I don't know why a depmod update is required, anyone feel free to answer that question?



Ubuntu 9.04:
 depmod -V
     module-init-tools 3.7-pre9
 gcc --version
     gcc (Ubuntu 4.3.3-5ubuntu4) 4.3.3

Debian lenny:
 depmod -V
     module-init-tools 3.4
 gcc --version
     gcc (Debian 4.3.2-1.1) 4.3.2


My reason for compiling on the Ubuntu system, is that its CPU is a
Core i7, which can compile the kernel in 5 minuts where the Debian
systems has a ATOM 330 CPU which uses 58 minuts to compile the same
kernel...

-- 
Med venlig hilsen / Best regards
  Jesper Brouer
  ComX Networks A/S
  Linux Network developer
  Cand. Scient Datalog / MSc.
  Author of http://adsl-optimizer.dk
  LinkedIn: http://www.linkedin.com/in/brouer

Re: (Solved) Problem compile kernel on Ubuntu and using on Debian

[Frans Pop]

Jesper Dangaard Brouer wrote:
> If you get past this one, by compiling enough modules into the kernel,
> BUT then a lot of modules does not seem to be loaded (modprobe).
[...] 
> Q: I don't know why a depmod update is required, anyone feel free to
> answer that question?

The most likely reason is that the two systems have different, and 
incompatible, versions of module-init-tools.

I've seen the same problem in the past [1] and, after a hefty discussion, 
accepted that you just _have_ to always run depmod -a after installing a 
kernel and before generating an initrd.

Cheers,
FJP

[1] http://bugs.debian.org/518407