gem2rpm

gem2rpm converts RubyGems packages to RPM spec files.

Installation

You can install gem2rpm as any other gem from RubyGems.org:

$ gem install gem2rpm

or download gem2rpm from Fedora repositories as RPM package:

# yum install rubygem-gem2rpm

Usage

Run gem2rpm --help to see all of the options.

At its simplest, download a gem (let's call it GEM) in its latest version (e.g. 1.2.3):

$ gem fetch GEM

and run gem2rpm:

$ gem2rpm GEM-1.2.3.gem

You can also use the --fetch flag to fetch the (latest) gem before generating the spec file, achieving the same effect as running 'gem fetch GEM' plus 'gem2rpm GEM-1.2.3.gem':

$ gem2rpm --fetch GEM

This will print an rpm spec file based on the information contained in the gem's spec file. In general, it is necessary to edit the generated spec file because the gem is missing some important information that is customarily provided in rpm's, most notably the license and the changelog.

Rather than editing the generated specfile, edit the template from which the specfile is generated. This will make it easier to update the RPM when a new version of the Gem becomes available.

To support this process, it is recommended to first save the default template somewhere:

$ gem2rpm -T > rubygem-GEM.spec.template

Now you can edit the template and then run gem2rpm to generate the spec file using the edited template:

$ gem2rpm -t rubygem-GEM.spec.template > rubygem-GEM.spec

With this new template you can now build your RPM as usual and when a new version of the gem becomes available, you just edit the saved template and rerun gem2rpm over it.

Templates

The template is a standard ERB file that comes with three main variables:

package - the Gem::Package for the gem
spec - the Gem::Specification for the gem (the same as format.spec)
config - the Gem2Rpm::Configuration that can redefine default macros or rules used in spec template helpers

The following variables still work, but are now deprecated:

format - The Gem::Format for the gem. Please note that this is kept just for compatibility reasons, since RubyGems 2.0 removed this class.

Template Configuration

To make the templates lighter and more complete, Gem2Rpm introduced in version 0.11.0 new configurable spec helpers such as spec.main_file_entries or spec.doc_file_entries that can be further configured via local config variable as follows:

# Change macros for Vagrant packaging
config.macros[:instdir] = '%{vagrant_plugin_instdir}'
config.macros[:libdir] = '%{vagrant_plugin_libdir}'

# Change what files go to the -doc sub-package
config.rules[:doc] = [/\/?doc(\/.*)?/]

To see all the defaults that can be changed (from https://github.com/fedora-ruby/gem2rpm/blob/master/lib/gem2rpm/configuration.rb):

$ irb -rgem2rpm
> Gem2Rpm::Configuration::DEFAULT_MACROS
> Gem2Rpm::Configuration::DEFAULT_RULES

Conventions

A typical source RPM for a gem should consist of three files: the gem file itself, the template for the spec file and the spec file. To ensure that the template will be included in the source RPM, it must be listed as one of the sources in the spec file.

The resulting RPMs should follow the naming convention 'rubygem-$GEM' where GEM is the name of the packaged gem. The default template also makes sure that the resulting package provides 'ruby($GEM)', according to general packaging conventions for scripting languages.

Limitiations

Because of the differences between the two packaging schemes, it is impossible to come up with a completely automated way of doing the conversion, but the spec files produced by this package should be good enough for most pure-ruby gems.