pyrox.dev
k3s: extend USAGE.md with package override instructions
closes #415969
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pkgs/applications/networking/cluster/k3s/docs/USAGE.md
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pkgs/applications/networking/cluster/k3s/docs/USAGE.md
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K3s has a config setting `prefer-bundled-bin` (and CLI flag `--prefer-bundled-bin`) that makes k3s use binaries from the `/var/lib/rancher/k3s/data/current/bin/aux/` directory, as unpacked by the k3s binary, before the system `$PATH`.
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This works with the official distribution of k3s but not with the package from nixpkgs, as it does not bundle the upstream binaries from [`k3s-root`](https://github.com/k3s-io/k3s-root) into the k3s binary.
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Thus the `prefer-bundled-bin` setting **cannot** be used to work around issues (like [this `mount` regression](https://github.com/util-linux/util-linux/issues/3474)) with binaries used/called by the kubelet.
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### Building from a different source
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Because the package is split into multiple derivations and the build process is generally more complex, it is not very obvious how to build k3s from a different source (fork or arbitrary commit).
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To build k3s from a different source, you must use `.override` together with `overrideBundleAttrs` (for the k3sBundle derivation) and another `.overrideAttrs` (for the final derivation):
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```nix
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{ fetchgit, k3s }:
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let
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k3sRepo = fetchgit {
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url = "https://github.com/k3s-io/k3s";
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rev = "99d91538b1327da933356c318dc8040335fbb66c";
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hash = "sha256-vVqZzVp0Tea27s8HDVq4SgqlbHBdZcFzNKmPFi0Yktk=";
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};
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vendorHash = "sha256-jrPVY+FVZV9wlbik/I35W8ChcLrHlYbLAwUYU16mJLM=";
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in
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(k3s.override {
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overrideBundleAttrs = {
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src = k3sRepo;
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inherit vendorHash;
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};
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}).overrideAttrs
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{
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src = k3sRepo;
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inherit vendorHash;
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}
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```
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- Additionally to `overrideBundleAttrs` there are also: `overrideCniPluginsAttrs` and `overrideContainerdAttrs`.
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- `k3s --version` still prints the commit SHA (`k3sCommit` passed into `builder.nix`) from the "base" package instead of the actually used `rev`.
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- Depending on the changes made in the fork / commit, the `k3s.override` (without the `overrideAttrs` of the final derivation) might already be enough.
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- If the commit is for a different version of k3s, make sure to use the correct "base" package, e.g., `k3s_1_31.override`. Otherwise the build fails with `Tagged version 'v1.33.1+k3s1' does not match expected version 'v1.31.9[+-]*'`
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- When adding an entirely new k3s version by calling `builder.nix`, keep in mind that the `k3sCommit` parameter is not used as the `k3sRepo` `rev` (it uses `v${k3sVersion}`). Therefore, you additionally must override the package, as shown above.