Reproducible Copr builds

14. 10. 2017 | Jakub Kadlčík | EN dev copr fedora

Well, sort of. Has your package failed to build in Copr? We introduce a new tool called copr-rpmbuild which allows you to reproduce it locally and make the debugging process much easier.

Behold copr-rpmbuild

copr-rpmbuild is a simple tool for reproducing Copr builds. Upon your needs, it can produce SRPM or RPM package. The best thing is that we use this tool internally within Copr infrastructure, so you can be sure that it reproduces the build under exactly same conditions.

The basic usage is straightforward

copr-rpmbuild --build-id <id> --chroot <name>

This will obtain a task definition from Copr and attempt to build RPM package into /var/lib/copr-rpmbuild/results/ directory. Except the binary package itself, there are also generated mock configs and logs.

If you are interested only in SRPM package, use

copr-rpmbuild --srpm --build-id <id>


Did I get you on the buzzword reproducible builds? Well, let me clarify what does it mean in this context. Copr stores a definition of every build. We call such definition a build task, and it contains information needed to create the desired buildroot and produce a package in it. For instance, there is a name of mock chroot that should be used, what repositories should be allowed there, what packages should be installed, … and of course information about what is going to be built in it.

The meaning of reproducing a build is creating a local build from the same task as the original one. It is not guaranteed that the output will always be a 100% same. It may vary when using a different mock version or non-standard configuration on a client side and in situations when the package operates with build timestamp of itself.


When no other config is specified, the pre-installed /etc/copr-rpmbuild/main.ini is used. This is also a configuration file used in Copr stack. You can specify a different config file by --config <path> parameter. Such config doesn’t necessarily have to contain all the possible options, just the ones that you want to change. Let me suggest two alternative configurations

User-friendly paths

Do not touch system directories.

resultdir = ~/copr-rpmbuild/results
lockfile = ~/copr-rpmbuild/lockfile
logfile = ~/copr-rpmbuild/main.log
pidfile = ~/copr-rpmbuild/pid

Different Copr instance

Use Copr staging instance as an example.

frontend_url =
distgit_lookaside_url =
distgit_clone_url =


# Default usage
copr-rpmbuild --build-id 123456 --chroot fedora-27-x86_64

# Build only SRPM package
copr-rpmbuild --srpm --build-id 123456

# Use different config
copr-rpmbuild -c ~/my-copr-rpmbuild.ini --build-id 123456 --chroot fedora-27-x86_64