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DefaultPolicy.md
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# Default Solver Policy A solver policy defines behaviour variables of the dependency solver. It decides which versions are considered newer than others, which packages should be preferred over others and whether operations like downgrades or uninstall are allowed. ## Selection of preferred Packages The following describe package pool situations with user requests and the resulting order in which the solver will try to install them. The rules are to be applied in the order of these descriptions. ### Repository priorities Packages Repo1.Av1, Repo2.Av1 * priority(Repo1) >= priority(Repo2) => (Repo1.Av1, Repo2.Av1) * priority(Repo1) < priority(Repo2) => (Repo2.Av1, Repo1.Av1) ### Package versions Packages: Av1, Av2, Av3 * Installed: Av2 Request: install A * (Av3) ### Virtual Packages (provides) Packages Av1, Bv1 * Av1 provides Xv1 * Bv1 provides Xv1 Request: install X * priority(Av1.repo) >= priority(Bv1.repo) => (Av1, Bv1) * priority(Av1.repo) < priority(Bv1.repo) => (Bv1, Av1) ### Package replacements Packages: Av1, Bv2 * Bv2 replaces Av1 Request: install A * priority(Av1.repo) >= priority(Bv2.repo) => (Av1, Bv2) * priority(Av1.repo) < priority(Bv2.repo) => (Bv2, Av1) Bv2 version is ignored, only the replacement version for A matters.