1 files changed, 67 insertions, 0 deletions
diff --git a/ops/nixos.nix b/ops/nixos.nix
new file mode 100644
index 0000000000..1442d89b30
--- /dev/null
+++ b/ops/nixos.nix
@@ -0,0 +1,67 @@
+# Helper functions for instantiating depot-compatible NixOS machines.
+{ depot, lib, pkgs, ... }@args:
+
+let inherit (lib) findFirst isAttrs;
+in rec {
+  # This provides our standard set of arguments to all NixOS modules.
+  baseModule = { ... }: {
+    # Ensure that pkgs == third_party.nix
+    nixpkgs.pkgs = depot.third_party.nixpkgs;
+    nix.nixPath =
+      let
+        # Due to nixpkgsBisectPath, pkgs.path is not always in the nix store
+        nixpkgsStorePath =
+          if lib.hasPrefix builtins.storeDir (toString pkgs.path)
+          then builtins.storePath pkgs.path # nixpkgs is already in the store
+          else pkgs.path; # we need to dump nixpkgs to the store either way
+      in
+      [
+        ("nixos=" + nixpkgsStorePath)
+        ("nixpkgs=" + nixpkgsStorePath)
+      ];
+  };
+
+  nixosFor = configuration: (depot.third_party.nixos {
+    configuration = { ... }: {
+      imports = [
+        baseModule
+        configuration
+      ];
+    };
+
+    specialArgs = {
+      inherit (args) depot;
+    };
+  });
+
+  findSystem = hostname:
+    (findFirst
+      (system: system.config.networking.hostName == hostname)
+      (throw "${hostname} is not a known NixOS host")
+      (map nixosFor depot.ops.machines.all-systems));
+
+  rebuild-system = rebuildSystemWith (
+    # HACK: use the string of the original source to avoid copying the whole
+    # depot into the store just for this
+    builtins.toString depot.path.origSrc);
+
+  rebuildSystemWith = depotPath: pkgs.writeShellScriptBin "rebuild-system" ''
+    set -ue
+    if [[ $EUID -ne 0 ]]; then
+      echo "Oh no! Only root is allowed to rebuild the system!" >&2
+      exit 1
+    fi
+
+    echo "Rebuilding NixOS for $HOSTNAME"
+    system=$(${pkgs.nix}/bin/nix-build -E "((import ${depotPath} {}).ops.nixos.findSystem \"$HOSTNAME\").system" --no-out-link --show-trace)
+
+    ${pkgs.nix}/bin/nix-env -p /nix/var/nix/profiles/system --set $system
+    $system/bin/switch-to-configuration switch
+  '';
+
+  # Systems that should be built in CI
+  whitbySystem = (nixosFor depot.ops.machines.whitby).system;
+  sandunySystem = (nixosFor depot.ops.machines.sanduny).system;
+  nixeryDev01System = (nixosFor depot.ops.machines.nixery-01).system;
+  meta.ci.targets = [ "sandunySystem" "whitbySystem" "nixeryDev01System" ];
+}