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Upgrades Hydra to the latest master/flake branch. To perform this upgrade, it's needed to do a non-trivial db-migration which provides a massive performance-improvement[1]. The basic ideas behind multi-step upgrades of services between NixOS versions have been gathered already[2]. For further context it's recommended to read this first. Basically, the following steps are needed: * Upgrade to a non-breaking version of Hydra with the db-changes (columns are still nullable here). If `system.stateVersion` is set to something older than 20.03, the package will be selected automatically, otherwise `pkgs.hydra-migration` needs to be used. * Run `hydra-backfill-ids` on the server. * Deploy either `pkgs.hydra-unstable` (for Hydra master) or `pkgs.hydra-flakes` (for flakes-support) to activate the optimization. The steps are also documented in the release-notes and in the module using `warnings`. `pkgs.hydra` has been removed as latest Hydra doesn't compile with `pkgs.nixStable` and to ensure a graceful migration using the newly introduced packages. To verify the approach, a simple vm-test has been added which verifies the migration steps. [1] https://github.com/NixOS/hydra/pull/711 [2] https://github.com/NixOS/nixpkgs/pull/82353#issuecomment-598269471
To build the manual, you need Nix installed on your system (no need
for NixOS). To install Nix, follow the instructions at
https://nixos.org/nix/download.html
When you have Nix on your system, in the root directory of the project
(i.e., `nixpkgs`), run:
nix-build nixos/release.nix -A manual.x86_64-linux
When this command successfully finishes, it will tell you where the
manual got generated.