Commit files for public release

nixos-configurations/lindberg-build/applications/README.md

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+# Nix Caches
+
+## Nixpkgs Cache
+
+To put less load on the upstream nixpkgs CDN and speed up builds, we run a (public) nixpkgs cache on [nixpkgs-cache.qo.is](https://nixpkgs-cache.qo.is). To use it, configure nix like follows in your `nix.conf`:
+
+```nix
+substituters = https://nixpkgs-cache.qo.is?priority=39
+```
+
+Note that the [cache.nixos.org](https://cache.nixos.org) public key must also be trusted:
+
+```nix
+trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
+```
+
+See the [nix documentation](https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-substituters) for details about substitutors.
+
+## Attic
+
+We use [attic](https://docs.attic.rs/) as a self hosted nix build cache.
+
+See [upstream documentation](https://docs.attic.rs/reference/attic-cli.html) for details on how to use it.
+
+### Server Administration
+
+Add users:
+
+```bash
+# For example, to generate a token for Alice with read-write access to any cache starting with `dev-` and read-only access to `prod`, expiring in 2 years:
+
+atticadm make-token --sub "alice" --validity "2y" --pull "dev-*" --push "dev-*" --pull "prod"
+```
+
+### Client Usage
+
+`attic login qois https://attic.qo.is <TOKEN_HERE>`
+
+`attic use qois:cachename`