pkg(docker-engine): fix static build with latest changes

[crazy-max]

follow-up moby/moby#44546

[crazy-max]

CentOS 7 packaging is broken when building from master branch: https://github.com/docker/packaging/actions/runs/3865721363/jobs/6589383289#step:7:898

#33 87.73 # github.com/docker/docker/daemon/graphdriver/btrfs
#33 87.73 daemon/graphdriver/btrfs/btrfs.go:12:30: fatal error: linux/btrfs_tree.h: No such file or directory
#33 87.73  #include <linux/btrfs_tree.h>

Looks related to moby/moby#44761 (moby/moby@3208dca).

So it seems it now requires 4.12 kernel looking at the first appearence in /usr/include/linux/btrfs_tree.h: torvalds/linux@fcc8487. Guess we need to build without btrfs support in such case or provide headers from a newer kernel. cc @neersighted

[neersighted]

Right, this is intentional. I would suggest simply compiling without Btrfs support as it's deprecated in CentOS (nee Red Hat) 7; this is what we plan to do in MCR/EE. There's no intention to backport to 20.10 so we don't take anything away from users.

Alternatively, it shouldn't be too burdensome to host an image on Docker Hub or similar that carries the results of:

• Setting up a system with the libc headers
• Fetching a tarball from kernel.org
• Running make headers_install

Then one could mount/copy those headers into the build environment of the CentOS 7 builder. However, I think given that it's very much on life-support in the distro itself means we should just skip building it, like we already do on 8+.

[crazy-max]

Yes there is also http://elrepo.org/tiki/kernel-lt

[neersighted]

Ah, good find; I had not realized that ELRepo provides full userspace headers (as opposed to kernel headers in /usr/src for module builds) -- I'll keep that in my back pocket if this comes up again. However I'd suggest just setting the buildtag for now and revisiting if it becomes a problem later.

[crazy-max]

Yes will do here:

packaging/pkg/docker-engine/scripts/pkg-rpm-build.sh

Lines 70 to 73 in 425085b

	centos8|centos9|oraclelinux*)
	rpmDefine+=(--define "_without_btrfs 1")
	export DOCKER_BUILDTAGS="exclude_graphdriver_btrfs $DOCKER_BUILDTAGS"
	;;

Thanks for your feedback

[crazy-max]

FWIW it works with:

yum install -y https://www.elrepo.org/elrepo-release-7.el7.elrepo.noarch.rpm
yum --enablerepo=elrepo-kernel -y install kernel-lt-headers

[thaJeztah]

@crazy-max how did you get it working for non-x86? Looks like the headers (even if they're "noarch") packages (or mirrors) are still x86; docker/docker-ce-packaging#810 (comment)

[crazy-max]

@crazy-max how did you get it working for non-x86? Looks like the headers (even if they're "noarch") packages (or mirrors) are still x86; docker/docker-ce-packaging#810 (comment)

I build without btrfs support in this PR and didn't try to install headers on non-x86 but it seems this repo don't support this arch unfortunately 😞

[thaJeztah]

SGTM