Most GNU/Linux systems use pretty sophisticated package managers, to ease the management of installed software. These keep track of all installed files, and various kinds of other necessary information, in special databases. On package installation, deinstallation, and upgrade, scripts are used that make all kinds of modifications to other parts of the system, making sure the packages get properly integrated.
This approach creates various problems. For one, all management has to be done with the distribution package management tools, or otherwise they would loose track of the system state. This is reinforced by the fact that the state information is stored in special databases, that only the special package management tools can work with.
Also, as changes to various parts of the system are made on certain events (installation/deinstallation/update), managing the various possible state transitions becomes very complex and bug-prone.
For the official (Hurd-based) GNU system, a different approach is intended: making use of Hurd translators -- more specifically their ability to present existing data in a different form -- the whole system state will be created on the fly, directly from the information provided by the individual packages. The visible system state is always a reflection of the sum of packages installed at a certain moment; it doesn't matter how this state came about. There are no global databases of any kind. (Some things might require caching for better performance, but this must happen transparently.)
The core of this approach is formed by stowfs. GNU Guix, GNU's package manager, installs each package in its own directory. Each user has a profile, which is the union of some of these packages. On GNU/Linux, this union is implemented as a symlink tree; on GNU/Hurd, stowfs would offer a more elegant solution. Stowfs creates a traditional Unix directory structure from all the files in the individual package directories. This handles the lowest level of package management.
The goal of this task is to exploit Hurd features in GNU Guix.
See also: Porting Guix to GNU/Hurd.
Possible mentors: Justus Winter (teythoon), Ludovic Courtès
Exercise: Make some improvement to any of the existing Hurd translators. Especially those in hurdextras are often quite rudimentary, and it shouldn't be hard to find something to improve.