Using Preferences to Tame your Package Manager

Overview

This paper appears to be for a talk, and starts by explaining why we need package managers, primarily because considering all combinations (e.g., of versions) is NP-complete. It then introduces the idea of using solvers that can honor user preferences to come up with a solution, and how it should be possible to honor user preferences. E.g.:

• “I want to minimize the number of packages I need to upgrade.”

and specifically highlights the opam package manager, which uses CUDF pivot format to represent these user preferences. An interesting idea is that the solver is modular, but doesn’t necessarily need to be alongside the software. They highlight making an external “solver farm” available (in the cloud) at their institution (Iril) for this purpose.

Takeaways

This talk might have introduced a novel idea of not just using modular solvers, but having them be based in the cloud so an entire community can use them from anywhere. The authors also seem to be suggesting that it’s best practice to use some kind of standard that also allows for user preferences (the one developed by the Mancoosi project) and then coming up with a solution (in CUDF format) that comes down to a list of changes to make on the system.

Terms

• OCaml is a programming langufage developed at Inria.
• OPAM is a package manager for OCaml

Mancoosi Project

The Mancoosi project was created to generally develop FOSS tools for sysadmins (e.g., package managers, and standards). This paper is concerned with it’s preference language, which describes using package selectors and measurement functions to control how dependency resolution is done by the manager.

Package Selectors

These identify a set of packages, e.g., solution, new, removed, changed, up, and down. For example, “changed” would be the set of packages that were changed in some proposed solution, S.

Measurements

An integer valued function that can be applied to any package selector, plus additional arguments. For example, I could do count(X) to count the number of entries in some set X. You should reference the second page of the PDF to see all the different measurement functions.

CUDF

See the [cudf] term page for notes from this paper.

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