Kernel build question

[Douglas Furlong]

On Tue, 2004-08-03 at 07:16 -0400, Robert P. J. Day wrote:
> On Tue, 3 Aug 2004, Edwin Dicker wrote:
> 
> > Hi all,
> >
> > I only unserstand some basics of kernel compiling. I understand that the
> > kernel source RPM comes with some configs for compiling the kernel. What I
> > would like to know is: Is the kernel binary RPM compiled with one of the
> > configs which are present in the kernel source RPM ?
> 
> on a fresh system, there's a good chance that the associated config 
> file is actually in /boot, with the name config-<whatever version>. 
> at least, that's a good place to start.
I believe the configuration file's in /usr/src/linux-version/configs/ are the ones
that are used to compile the kernels in the first place, so if one was
to recompile the kernel using one of those files they should have
exactly the same kernel as the one that they get when installing the
kernel RPM.
> rday
> 
> p.s.  the 2.6 kernel comes with a config option to bury the config 
> file inside the actual kernel itself.  IIRC, to get at that file, 
> you'd use a utility called extract-ikconfig.
This option has to be enabled and currently is not, it is disabled by
default due to the added size imposed when using it.


Kernel .config support (IKCONFIG)

This option enables the complete Linux kernel ".config" file
contents, information on compiler used to build the kernel,
kernel running when this kernel was built and kernel version
from Makefile to be saved in the kernel. It provides documentation
of which kernel options are used in a running kernel or in an
on-disk kernel. This information can be extracted from the kernel
image file with the script scripts/extract-ikconfig and used as
input to rebuild the current kernel or to build another kernel.
It can also be extracted from a running kernel by reading
/proc/config.gz and /proc/config_built_with, if enabled (below).
/proc/config.gz will list the configuration that was used
to build the kernel and /proc/config_built_with will list
information on the compiler and host machine that was used to
build the kernel.

And

Enable access to .config through /proc/config.gz (IKCONFIG_PROC)

This option enables access to kernel configuration file and build
information through /proc/config.gz.


These options are under "General setup" when doing an make xconfig


Hope this helps

-- 
Douglas Furlong
Systems Administrator
Firebox.com
T: 0870 420 4475        F: 0870 220 2178
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