Imposing a memory management discipline on software deployment

The deployment of software components frequently fails because dependencies on other components are not declared explicitly or are declared imprecisely. This results in an incomplete reproduction of the environment necessary for proper operation, or in interference between incompatible variants. In this paper, we show that these deployment hazards are similar to pointer hazards in memory models of programming languages and can be countered by imposing a memory management discipline on software deployment. Based on this analysis, we have developed a generic, platform and language independent, discipline for deployment that allows precise dependency verification; exact identification of component variants; computation of complete closures containing all components on which a component depends; maximal sharing of components between such closures; and concurrent installation of revisions and variants of components. We have implemented the approach in the Nix deployment system, and used it for the deployment of a large number of existing Linux packages. We compare its effectiveness to other deployment systems.