Introduction

You can build a "Hello, World" RPM either with the native tools or with mock using these walk-through instructions.

Keep in mind when this program builds, that it is no ordinary "Hello, World" program. It's a "Hello, World" program on steroids. It even has internationalization support.

The walk-through below is for illustrative and educational use only. These steps are not necessarily how such a process would be advised for general development use.

For further information on mock, see: https://rpm-software-management.github.io/mock/

Building RPMs Natively

Prep your system with the necessary packages:

$ sudo yum install -y git yum-utils rpmdevtools rpm-build gcc make

Prep your home directory area for building RPMs:

$ rpmdev-setuptree
$ ls -l .rpmmacros rpmbuild

Clone the "Hello, World" repository and change to the SPECS directory:

$ git clone git@github.com:qbarnes/hello-rpm.git
$ cd hello-rpm/SPECS

Install the packages needed to build the Source RPM (all may already be installed):

$ sudo yum-builddep -y hello.spec

Download the "Hello, World" tarball into your %{_sourcedir} directory (typically ~/rpmbuild/SOURCES):

$ spectool -g -R hello.spec

Now to build the binary RPMs into your %{_topdir}/RPMS/* directories (typically ~/rpmbuild/RPMS/*):

$ rpmbuild -bb hello.spec

The RPMs can be viewed with:

$ ls -l $(rpm -E '%{_topdir}')/RPMS/$(arch)/hello*.rpm

Building RPMs Using Mock

Prep your system with the necessary packages:

$ sudo yum install -y git yum-utils rpmdevtools

Now install mock:

$ sudo yum install -y mock

If the above command failed, you may need to install and enable EPEL. To install EPEL on your system, follow these directions, then run:

$ sudo yum install -y --enablerepo=epel mock

Once the mock package is installed, add yourself to the mock user group:

$ sudo usermod -aG mock "$USER"

You don't have to add yourself to the mock user group. If you don't, you'll have to run mock below using sudo.

Before continuing, you'll need to log out and log back in to update your credentials.

Clone the "Hello, World" repository:

$ git clone git@github.com:qbarnes/hello-rpm.git

Change to the hello-rpm directory and prep it for building the RPMs:

$ cd hello-rpm
$ sudo yum-builddep -y SPECS/hello.spec
$ mkdir SOURCES
$ spectool -g -C SOURCES SPECS/hello.spec

The first time you run mock, it'll take much longer than other runs because mock downloads and caches the upstream yum repository data and the package's dependent packages.

To build the hello-rpm source RPM for your currently running system using mock, ensure you're still in the top directory of the cloned repo and then run:

$ mock \
    --resultdir=results_srpm \
    --buildsrpm \
    --spec SPECS/hello.spec --sources SOURCES

Look under the results_srpm directory to see your new SRPM and log files from its build:

$ ls -l results_srpm

Let's now build the binary RPMs from its SRPM by running:

$ mock \
    --resultdir=results_rpms \
    --rebuild results_srpm/hello-*.src.rpm

Look under results_rpms:

$ ls -l results_rpms

You'll see not only the hello binary RPMs, but a new hello-*.src.rpm too. That's because the provided source rpm might have been from another distro's repository (e.g. OpenSUSE or Alma). This new SRPM would be rebuilt for the target platform.

With mock, you don't have to build RPMs for the host system. You can build for other platforms too.

For example, to make RHEL 7 "Hello, World" RPMs by using the source RPM first built above, run:

$ mock -r epel-7-$(arch) \
    --resultdir=results_el7_rpms \
    --rebuild results_srpm/hello-*.src.rpm
$ ls -l results_el7_rpms

You can look under /etc/mock to see what possible configurations are supported as build targets.

Note though, don't go "forward" (e.g. trying to build RHEL 8 RPMs using a RHEL 7 host). It may appear to work sometimes, but that'll just be arbitrary luck if it happens to succeed.

For those wanting to know what's beyond mock, you may want to read about:

Tito - A tool for managing RPM based projects using git for their source code repositories
Koji - A tool for building trees of RPMs
COPR and Open Build Service - Package build service engines