nikstur
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This establishes a repeatable and clear process for preparing and testing changes to systemd. It should help existing maintainers to follow a consistent process with clear judgment (when these tests pass, the change is good to merge) and potential new maintainers.
87 lines
3.1 KiB
Markdown
87 lines
3.1 KiB
Markdown
# Maintaining systemd
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This document guides you through some of the important parts of maintaining
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systemd.
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## Preparing and Testing Changes
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Changing systemd (most importantly updating!) is quite cumbersome:
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- It is very close to the root of the dependency tree and thus causes rebuilds
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of a lot of packages. It always needs to target staging.
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- ALL tests need to be rebuilt if systemd changes because systemd is a
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mandatory part of NixOS.
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To alleviate this, we have a special procedure for preparing and testing
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changes to systemd. It is quite different from maintaining other packages in
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Nixpkgs. Please read this carefully if you want to open a PR for systemd.
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1. In your fork of Nixpkgs, create a new branch from the merge base of the
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master branch and staging. Changes to systemd need to target staging and
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this helps to keep the number of rebuilds minimal.
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```sh
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git switch --create systemd-changes $(git merge-base upstream/master upstream/staging)
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```
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2. Change the systemd package. Test it by (1) building the systemd package and
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(2) building `systemd.nixosTests.simple-vm`. When this is successful, commit the
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changes.
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3. Check out master again and add your new branch to a new worktree.
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```sh
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git switch master
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git worktree add ../systemd-changes systemd-changes
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```
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4. Apply this patch to your master checkout of Nixpkgs so that all tests use
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the systemd package from the newly created worktree. This allows you to only
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rebuild the systemd package itself without having to build all the other
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packages that depend on systemd. Note that the path for `systemdTest` in
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this patch will depend on the name of your worktree.
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```patch
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diff --git i/nixos/modules/module-list.nix w/nixos/modules/module-list.nix
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index c57b627e875c..89f026efd786 100644
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--- i/nixos/modules/module-list.nix
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+++ w/nixos/modules/module-list.nix
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@@ -2040,4 +2040,5 @@
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./image/repart.nix
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];
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}
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+ ({ pkgs, ... }: {systemd.package = pkgs.systemdTest;})
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]
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diff --git i/pkgs/top-level/all-packages.nix w/pkgs/top-level/all-packages.nix
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index 0e2defb6566c..c60c1f201828 100644
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--- i/pkgs/top-level/all-packages.nix
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+++ w/pkgs/top-level/all-packages.nix
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@@ -8538,6 +8538,10 @@ with pkgs;
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libsysprof-capture = callPackage ../development/tools/profiling/sysprof/capture.nix { };
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+ systemdTest = callPackage ../../../systemd-changes/pkgs/os-specific/linux/systemd {
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+ # break some cyclic dependencies
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+ util-linux = util-linuxMinimal;
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+ };
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systemd = callPackage ../os-specific/linux/systemd {
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# break some cyclic dependencies
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util-linux = util-linuxMinimal;
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```
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5. Build all the systemd NixOS tests
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```sh
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nix-build -A systemd.nixosTests
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```
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You are encouraged to use a tool like [brr](https://github.com/nikstur/brr) or
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[nix-fast-build](https://github.com/Mic92/nix-fast-build) to speed up
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evaluation and building all these tests.
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In conclusion, there are three quality gates for changes to systemd:
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1. The package needs to build on staging.
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2. The test `systemd.nixosTests.simple-vm` needs to pass on staging.
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3. All `systemd.nixosTests` must pass on master with the changed systemd from a separate worktree.
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