Differences between /proc/config.gz and developer container's configuration

[Gianluca Borello]

Hi,

Starting from a few releases ago, there seems to be an inconsistency between the kernel configuration file found in the developer container, and the one for the running kernel:

CoreOS alpha (1164.1.0)

$ zcat /proc/config.gz > ~/config

$ diff ~/config /usr/boot/config-4.7.3-coreos

186,188c186

< CONFIG_INITRAMFS_SOURCE="bootengine.cpio"

< CONFIG_INITRAMFS_ROOT_UID=0

< CONFIG_INITRAMFS_ROOT_GID=0

---

> CONFIG_INITRAMFS_SOURCE=""

This is creating some minor problems when we precompile the kernel module for sysdig. It's not a big deal, since CoreOS is also now shipping the kernel headers on any base image, giving us the option to compile the kernel module at runtime, but I'm just checking if the change is expected.

Thanks

[david....@coreos.com]

Hi,

Yes, this is expected.  The kernel build process was changed a few releases ago to build in two phases: first the modules, then the kernel itself.  The initramfs image is built during the second phase where it can include the pre-built modules, and that is where the config option now gets set.  See:

https://github.com/coreos/coreos-overlay/blob/master/sys-kernel/coreos-kernel/coreos-kernel-4.7.3.ebuild#L62

Thanks.

David