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We're trying to build a piece of software that demands the kernel source, not just the headers. So we downloaded the kernel source via the centos src rpm.

However the autoconf.h is missing.

We tried

  • Put the .config in place (copied the one from /boot).

  • run make oldconfig

So what is creating the autoconf.h file? Do we actually have to build the kernel?

SaveTheRbtz
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Stefan
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  • In case someone is using Kconfig as build architecture for a project not related to Linux, the answer to this question is a bit different: to generate autoconf.h you need ./kconfig-frontends/frontends/conf/conf --silentoldconfig Kconfig – Étienne Aug 14 '14 at 15:49

2 Answers2

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The file include/generated/autoconf.h is generated in the make prepare step. If you are trying to build a kernel module, you will also need the make scripts step:

gunzip < /proc/config.gz > .config
make oldconfig
make prepare
make scripts

Usually the kernel is accompied with a headers package, have you tried installing that first? For CentOS, try installing the kernel-devel package. Details can be found on http://wiki.centos.org/HowTos/I_need_the_Kernel_Source

Lekensteyn
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  • Thanks! Yes, we had the headers package installed, but for some reasons the configure script was demanding the full source. We used the wiki page you linked. – Stefan Jan 20 '14 at 16:22
  • Just for completeness: on CentOS the kernel config is located in `/boot` (compare with `uname -r` to select the right one). – Stefan Jan 20 '14 at 16:25
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    @Stefan On some distros (like Arch Linux) it is located in `/lib/modules/$(uname -r)/build/.config` (`build` usually symlinks to `/usr/src/linux-$(uname -r)`), others use `/boot/config-$(uname -r)` (such as Ubuntu, Debian and apparently CentOS). If enabled during compilation, it is also available from `/proc/config.gz`. – Lekensteyn Jan 20 '14 at 19:56
0

The file autoconf.h is automatically generated during the build process from the .conf file. Many kernel source files use autoconf.h.

Behnam Dezfouli
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    Welcome to Server Fault! We prefer additional answers to address the question in a way that previous answers did not, or provide a better solution. – Falcon Momot Aug 31 '15 at 02:28