Build a RPM package and publish it on Copr

May 20, 2018

Disclaimer: I'm not a linux packaging expert, some parts could be considered as bad practises. Moreover, there are billions different ways of building packages. I am proposing only one in this article.

Setup

First of all, we will need some tools to build packages:

sudo dnf install git rpmdevtools rpm-build

RPM is a bit special, as it needs its own folder hierarchy (stored by default in ~/rpmbuild) and can't build without this hierarchy. It's a bit annoying when you manage your packages in different repositories. We will see one way to get around this problem.

First, create a git repository for your RPMs:

mkdir my-rpms && cd my-rpms
git init

We will create one folder for each RPM and initialize with the essence of a RPM: a spec file. For now, let's start with only one, chez-scheme which is a real example:

mkdir chez-scheme && cd chez-scheme
rpmdev-newspec --macros chez-scheme.spec

You should have generated the following file:

Name:           chez-scheme
Version:        
Release:        1%{?dist}
Summary:        

License:        
URL:            
Source0:        

BuildRequires:  
Requires:       

%description


%prep
%autosetup

%build
%configure
%make_build


%install
rm -rf %{buildroot}
%make_install


%files
%license add-license-file-here
%doc add-docs-here

%changelog
* Sun May 20 2018 Quentin Dufour <quentin@dufour.io>
- 

So, now we must fill this file. You can use the Fedora Packaging Guidelines guide to find help for the different macro (lines starting with a percent). You can also take some inspiration from existing .spec files like meshlab.spec or chez-scheme.spec.

Sources and patches

We will consider the case where a source tarball is provided, but you need to patch it. You can easily retrieve a tarball from any github or gitlab project, for a given release, like:

Source0: https://github.com/cisco/ChezScheme/archive/v%{version}.tar.gz

By templating the link, it will be easier to upgrade the package.

To create the patches, you have different options. You can either clone the repository, do the modification in a specific branch or commit, then generate a patch:

git checkout -b v9.5-patches
git commit -m "A first patch"
git commit -m "A second patch"
git format-patch v9.5

Another way is to download and extract the tarball, create a copy and use diff:

tar xf v9.5.tar.gz
cp -r v9.5 v9.5-src
# modify v9.5
diff -Naur v9.5-src v9.5 > some-modification.patch

We will put these patches in our git repository, next to our .spec file:

rpm
└── chez-scheme
    ├── chez-scheme.spec
    ├── chez-scheme-symlink.patch
    └── chez-scheme-xlocale.patch

Applying patches and extracting tarball can lead to some problems.

First, patches can have different "roots". We will use patch -p0 to apply git patches as they don't include the main folder and patch -p1 for diff patches as they include the main folder. If you use the autosetup macro in your .spec file, you will put (for diff patches):

%autosetup -p1

Second, once downloaded, your tarball doesn't necessarily extract in a folder of the name <package>-<version>. If it's not the case, you must precise it too:

%autosetup -p1 -n ChezScheme-%{version}

Now, if we want to build the RPM, we will have to type the following commands:

spectool -g -R ./chez-scheme.spec  # Download sources
cp *.patch ~/rpmbuild/SOURCES      # Copy patches
rpmbuild -ba ./chez-scheme.spec    # Build RPM

There are some tools like rpkg, fedpkg or tito that can do most of the steps for you. Unfortunately, they are not very flexible. rpkg and fedpkg never download the source directly, but from a mirror, and fails with a 404 as they don't find the file. If I want to push my source to this mirror, it fails with an unauthorized error. These packages seem to be aimed at distribution maintainers. tito, for its part, doesn't handle correctly patches and sources. It consider that everything should be embedded in a single git repository.

So, we will need an home made solution.

make srpm

Fortunately, copr propose different solutions. One is to build your .srpm locally and send it to copr, but we can even avoid this step and only give a git repository to copr: we will build our own builder with a Makefile.

Copr will call a Makefile located in <git_root>/.copr from the folder of our package (<git_root>/chez-scheme) and call:

make -f <git_root>/.copr/Makefile srpm outdir="<outdir>" spec="<spec_path>"

Copr proposes a simple Makefile in its documentation. I'm proposing a bit more complex one that use only rpmbuild:

rpmbuild_src = $(shell rpmbuild --eval '%{_sourcedir}')
.PHONY: prepare srpm rpm

prepare:
	dnf -y install rpmdevtools rpm-build
	cp *.patch $(rpmbuild_src)
	spectool -g -R $(spec)

srpm: prepare
	rpmbuild -bs --define "_srcrpmdir $(outdir)" $(spec)

rpm: prepare
	rpmbuild -bb --define "_rpmdir $(outdir)" $(spec)

The rpm target will not be used by Copr but it can be convenient to locally test your package build before sending it to Copr.

Your folder structure should now look like this:

rpm
├── chez-scheme
│   ├── chez-scheme.spec
│   ├── chez-scheme-symlink.patch
│   └── chez-scheme-xlocale.patch
└─── .copr
    └── Makefile

You really have to put the Makefile here, otherwise copr will not find it.

Use Copr

Now you just need to commit + push your repository and use the Copr web interface to create a new project, add a package and trigger a build !

After that, your users can just enable the copr repository on their system and install your package:

sudo dnf copr enable superboum/chez-scheme 
sudo dnf install chez-scheme

You can configure some webhooks to rebuild your packages for each git commit. And that's all!

Sources