Backporting is the action of taking parts from a newer version of a software systemorsoftware component and porting them to an older version of the same software. It forms part of the maintenance step in a software development process, and it is commonly used for fixing security issues in older versions of the software and also for providing new features to older versions.
The simplest and probably most common situation of backporting is a fixed security hole in a newer version of a piece of software. Consider this simplified example:
By taking the modification that fixes Software v2.0 and changing it so that it applies to Software v1.0, one has effectively backported the fix.[1]
In real-life situations, the modifications that a single aspect of the software has undergone may be simple (only a few lines of code have changed) up to heavy and massive (many modifications spread across multiple files of the code). In the latter case, backporting may become tedious and inefficient and should only be undertaken if the older version of the software is really needed in favour of the newer (if, for example, the newer version still suffers stability problems that prevent its use in mission-critical situations).[2]
The process of backporting can be roughly divided into these steps:[1]
Usually, multiple such modifications are bundled in a patch set.
Backports can be provided by the core developer group of the software. Since backporting needs access to the source code of a piece of software, this is the only way that backporting is done for closed source software – the backports will usually be incorporated in binary upgrades along the old version line of the software. With open-source software, backports are sometimes created by software distributors and later sent upstream (that is, submitted to the core developers of the afflicted software).[2]