This plugin allows you to (on demand) export the Mock chroot as an OCI image in local archive format (tarball). This tarball can provide additional convenience for local build reproducibility. See the example below for details.

By default, this plugin is disabled. You can enable it using the --enable-plugin export_buildroot_image option in --rebuild mode.

This plugin has been added in Mock v6.0.

Example use-case

First, let’s start a standard Mock build, but enable the OCI archive generator:

$ mock -r fedora-rawhide-x86_64 --enable-plugin export_buildroot_image \
        /tmp/quick-package/dummy-pkg-20241212_1114-1.src.rpm
... mock installs all build-deps, and does other chroot tweaks ...
Start: producing buildroot as OCI image
... mock performs the rpmbuild ...
INFO: Results and/or logs in: /var/lib/mock/fedora-rawhide-x86_64/result
Finish: run

The archive has been saved in the result directory:

$ ls /var/lib/mock/fedora-rawhide-x86_64/result/*.tar
/var/lib/mock/fedora-rawhide-x86_64/result/buildroot-oci.tar

You may use this tarball together with the --buildroot-image option then. But also, you can try re-running the build without Mock, like this:

$ chmod a+r /tmp/quick-package/dummy-pkg-20241212_1114-1.src.rpm
$ podman run --rm -ti \
    -v /tmp/quick-package/dummy-pkg-20241212_1114-1.src.rpm:/dummy-pkg.src.rpm:z \
    oci-archive:/var/lib/mock/fedora-rawhide-x86_64/result/buildroot-oci.tar \
    rpmbuild --rebuild /dummy-pkg.src.rpm

Installing /dummy-pkg.src.rpm
setting SOURCE_DATE_EPOCH=1401926400
Executing(%mkbuilddir): /bin/sh -e /var/tmp/rpm-tmp.XIm441
...
Executing(%prep): /bin/sh -e /var/tmp/rpm-tmp.pqJ9hu
...
Executing(%build): /bin/sh -e /var/tmp/rpm-tmp.iaeMZG
...
Executing(%install): /bin/sh -e /var/tmp/rpm-tmp.SHktaE
...
Processing files: dummy-pkg-20241212_1114-1.fc42.x86_64
...
Executing(%clean): /bin/sh -e /var/tmp/rpm-tmp.E71FWH
...
+ exit 0

Warning: This method of reproducing a Mock build is not recommended for production use. During a normal/full Mock rebuild, Mock ensures the buildroot is fully up-to-date. Using just plain rpmbuild within Podman may result in outdated files, different structure in the kernel-driven filesystems like /proc, /dev, and /sys, different SELinux assumptions, permissions, etc. Proceed with caution, and be prepared to encounter some differences (and perhaps different build failures).