WARNING! This article has been written a long time ago. It may no longer represent the current views of the author!

Notes: Rebuiling RPM packages with mock

DISCLAIMER: this is not meant to be coherent post. Sorry. Just notes for future reference.

Given a source RPM package in order to rebuild it I use following tools. For detailed description about what and why I suggest looking at the RPM Packaging Guide first (really nice resource for first-time packagers!).

Installing needed tools on Centos 7 (and other RHEL derivatives, btw RHEL8 shouldn't change this) would look like this:

sudo yum install -y epel-release
sudo yum install -y rpm-build rpmdevtools mock yum-utils

Now for standard rebuiling we need to setup the correct directory structure:

$ rpmdev-setuptreeo
$ tree -L 1 ~/rpmbuild
|-- RPMS

5 directories, 0 files

Now when we have a source package we need to unpack it in correct subdirectiories, if the package is called llvm3.9-3.9.1-7.el7.src.rpm then command looks like this:

rpm --install llvm3.9-3.9.1-7.el7.src.rpm

This will put all files in correct places for you. Note: no need for superuser privilages (unless you're building as root, but that is discouraged).

Next step is to take care of the dependencies for the package we are building:

sudo yum-builddep ~/rpmbuild/SPECS/llvm3.9.spec

Now for a rebuild:

rpmbuild -ba ~/rpmbuild/SPECS/llvm3.9.spec

If it doesn't work try installing @buildsys-build. This will install all needed compilers and standard (in terms of C/C++) build tools.

Building with mock

Now, we want to be able to build the package without worrying that we have not specified some build dependency in the specfile. mock comes to the rescue!

In order to build something with mock we need to have the SRPM. With the above rpmbuild command we get the file as well, but if you want to just create the SRPM from scratch run:

rpmbuild -bs ~/rpmbuild/SPECS/llvm3.9.spec

The .src.rpm will be in the ~/rpmbuild/SRPMS/ directory.

For building with mock the user that will be running the command needs to be in the mock group. To add current user we simply can:

sudo usermod -a -G mock $USER

Now, we need a session where the user is in fact recognized as part of the group. Supposedly, this is the solution in some environments (I couldn't make it work with graphical session)

newgrp -

Ok. Here we can start actually building. mock needs to know what evironment it is supposed to 'emulate' or rather - recreate. Under /etc/mock/ you can find a plethora of different configurations (mostly, Fedora and EPEL for different versions). You can work out the syntax from different sources.

Building now is as simple as running:

mock -r $CONFIG --rebuild package.src.rpm

where you specify the CONFIG for the package to be built with.

Setting builder hostname

Supposedly, setting a macro we can change the hostname of the building machine

# here CONFIG points to something in /etc/mock e.g. epel-7-x86_64
mock -r $CONFIG -D "_buildhost NAME" package-1.0-1.el7.x86_64.src.rpm

More useful info in site-defaults.cfg from the mock repo.

Other way is to have a custom mock.cfg (note, Python-like syntax):

config_opts['hostname'] = 'my.own.hostname'

There are some packages that will misbehave though. See mysql-community. But I guess that's the exception from the rule.

Other useful resources