Revisor is a community product by Fedora Unity. Amongst other features, it allows the creation of installation media and live media in the easiest possible manner, through a click-and-go GUI. This chapter gives some insight on how and why Revisor was born, and how the product evolved since.
Revisor development started in December 2006, during the Fedora 7 development cycle, in which -as you might recall- the Fedora Core repository, maintained by Red Hat, and Fedora Extras repository, mostly maintained by the community, were merged into one large repository being maintained by both community members as well as Red Hat employees -which are mostly community members who just so happen to be hired by Red Hat, so community altogether. Before then Red Hat employees maintained Fedora Core -as the set of packages upstream for Red Hat's Enterprise product- and the community maintained a repository with additional software; Fedora Extras. Red Hat composed the Fedora distribution every once in a while, but the merge introduced the possibility for packages that were in Fedora Extras to be included in the main distribution, and for the community to also (co-)maintain the (former) Fedora Core packages that originally made up the distribution.
In addition to this huge merge of packages, Red Hat employees were also able to release the entire build process to the community, meaning that from the moment the source is committed up and until the release is announced, the entire process is open. Not that is was all behind closed doors or proprietary or anything, the community just couldn't really play with it as much. We now have koji (build system), mash (repository compose from build system products), bodhi (updates release system), livecd-tools (compose tool for live media) and pungi (compose tool for installation media).
Composing media was an obscure process up and until the moment these tools exposed the best way to compose (a set of) installation media. Fedora Unity had been building and releasing so-called Re-Spins1 regularly, but they were built using a not-so-very intelligent bash script. Like hundreds if not thousands of other parties that needed to build their own media one way or the other, the entire process was based on the best educated guess of what should happen. Luckily, in the FOSS world an educated guess is often a very good guess, despite the fact that one keeps learning even years after the original engagement.
When in December 2006 the compose tools hit a stage in which they were released to the public, Fedora Unity was eager to get these tools and study them and use them for composing their Re-Spins. Up and until then, Re-Spins were composed with the aforementioned bash script that didn't do much but trigger the appropriate commands in a sequence; There wasn't any dependency resolving between the packages included nor did we know exactly how a release was supposed to be composed -it was our educated guess of how it could happen. Although it often led to success, we've had many, many failed Re-Spins as well. With a handful of volunteers, you can imagine the amount of frustration that might give. Fedora Unity was eager to improve their Re-Spin process.
So, early February 2007, a number of Fedora Unity members attended “FUDCon 2007” in Boston, and presented a working GUI front-end to both livecd-tools and pungi enabling regular users to also re-compose or re-spin the installation media and live media they had been getting from the Fedora Project. Revisor at this point just made it “as easy as possible”. Besides the possibilities of pungi and livecd-tools themselves, the wizard Revisor had apparently was very, very useful to mere mortals. From that point on, things took off.
Fedora Unity decided Revisor could accomplish more then just being a front-end to existing compose tools and enable someone to tweak a lot of settings as well. In March 2007, Revisor was rebuilt from the ground up in order to allow a more flexible process, neing more dependent on the configuration directives it was given from configuration files, command-line parameters and the graphical user interface, and less so on the processes of the existing tools. When in San Diego at the Red Hat Summit (early May 2007), Robert 'Bob' Jensen and Jonathan Steffan gave a presentation on “Customizing Fedora”, the responses were amazing. Since then Revisor has evolved from a front-end to existing tools to the complete compose tool it is today, with lots of configuration options for specific use-cases.
For users, Revisor is particularly useful because it has a GUI front-end wizard, which, with the defaults settings, will just succeed in getting a user the media he/she wants. If a user decides he needs little adjustment of the media, the GUI allows for selecting the most common options. If a user decides he needs some less common adjustments, the configuration options gives him very granular control -and as long as the documentation on all the options is sufficient, users will be able to make those less common adjustments.
For administrators on the other hand, Revisor is the tool that gives so much granular control over what happens, that it can serve almost every specific use-case. In this aspect, Revisor could potentially replace the compose tools administrators have been developing themselves with a consistent and flexible program flow.
This document should enable you to study the process of composing installation and live media, and comprehend the logic Revisor adds to that process.
