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Modularity Architecture
This page needs to be rewritten
Modularity reuses some existing and creates some new concepts in the build and release process in Fedora.
Packages
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We are reusing packages as they are.
Packages are the smallest unit of software delivery. Right now, Fedora uses RPM packages to build and ship all of its software. There is a distinction between source RPM (SRPM) packages and binary RPM packages.
As the name suggests, *source packages* contain the source code, but also the build process definition including a list of build dependencies. Building a source package results in one or multiple binary packages.
*Binary packages* are produced by building source packages in a build environment called a buildroot.
Different buildroots produce different binary packages.
This means that a source package without a context is not a complete definition of a resulting binary package.
Every Fedora release has its own buildroot. Even when multiple releases contain the same package using the same source, they are built multiple times, once in each buildroot, producing different (and often incompatible) binary packages. Also, over time, as the distribution gets updated, so does its buildroot. As a result, a package built today may not result in the same binary as a package built tomorrow.
*Packages are either a part of a release, or a part of a module.*
Releases
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Releases are the generations of Fedora e.g. “Fedora 28”, “Fedora 29”, or “EPEL 7”.
Each release can only contain one major version of every package (by policy). In general, Fedora tends to ship the latest stable versions of software available. At the same time, packages need to maintain a certain API/ABI stability throughout the life cycle of the release they are part of.
The problem with this approach is finding the right balance of being too fast vs. too slow. For example, developers in general tend to prefer the newest versions of software, while server administrators want API/ABI stability for a longer period of time. This problem is solved by Modules.
Modules and Streams
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*Modules* are collections of packages representing a logical unit e.g. an application, a language stack, a set of tools.
These packages are built, tested, and released together.
Each module defines its own life cycle which is closer to the upstream rather than the Fedora release.