From f35a79444c26269d02fbfb0316f30f78b8cc93e7 Mon Sep 17 00:00:00 2001
From: Luke Granger-Brown <hg@lukegb.com>
Date: Fri, 31 Dec 2021 23:51:09 +0000
Subject: [PATCH] ops/nixos: add better support for specialisations

---
 ops/nixos/lib/common.nix         | 27 +++++++++++++++++++--------
 ops/nixos/lib/rebuilder.nix      | 11 +++++++++--
 ops/nixos/porcorosso/default.nix |  1 +
 3 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/ops/nixos/lib/common.nix b/ops/nixos/lib/common.nix
index abf1a1e34a..29e944bb7c 100644
--- a/ops/nixos/lib/common.nix
+++ b/ops/nixos/lib/common.nix
@@ -11,6 +11,11 @@ in
 {
   imports = [ ../../../third_party/home-manager/nixos ];
 
+  options.my.specialisationName = lib.mkOption {
+    type = lib.types.nullOr lib.types.str;
+    default = null;
+  };
+
   options.my.rundeck.hostname = lib.mkOption {
     type = lib.types.str;
     default = config.networking.fqdn;
@@ -213,24 +218,30 @@ in
       text = ''
         test -d /run/prometheus-textfile-exports || mkdir /run/prometheus-textfile-exports
         my_version_string="$(cat "$systemConfig/nixos-version")"
-        my_hash_string="$(readlink -f "$systemConfig" | grep -Eo '\b[0-9a-df-np-sv-z]{32}\b')"
-        echo "nixos_running_system{version=\"$my_version_string\", hash=\"$my_hash_string\"} 1" > /run/prometheus-textfile-exports/running_system.prom
+        my_hash_string="$(readlink -f "$systemConfig" | ${pkgs.gnugrep}/bin/grep -Eo '\b[0-9a-df-np-sv-z]{32}\b')"
+        my_specialisation="$(cat "$systemConfig/specialisation-name" 2>/dev/null || true)"
+        echo "nixos_running_system{version=\"$my_version_string\", hash=\"$my_hash_string\", specialisation=\"$my_specialisation\"} 1" > /run/prometheus-textfile-exports/running_system.prom
 
         my_version_string="$(cat "/run/booted-system/nixos-version")"
-        my_hash_string="$(readlink -f "/run/booted-system" | grep -Eo '\b[0-9a-df-np-sv-z]{32}\b')"
-        echo "nixos_booted_system{version=\"$my_version_string\", hash=\"$my_hash_string\"} 1" > /run/prometheus-textfile-exports/booted_system.prom
+        my_hash_string="$(readlink -f "/run/booted-system" | ${pkgs.gnugrep}/bin/grep -Eo '\b[0-9a-df-np-sv-z]{32}\b')"
+        my_specialisation="$(cat "/run/booted-system/specialisation-name" 2>/dev/null || true)"
+        echo "nixos_booted_system{version=\"$my_version_string\", hash=\"$my_hash_string\", specialisation=\"$my_specialisation\"} 1" > /run/prometheus-textfile-exports/booted_system.prom
       '';
     };
     boot.postBootCommands = lib.mkAfter ''
       test -d /run/prometheus-textfile-exports || mkdir /run/prometheus-textfile-exports
       my_version_string="$(cat "/run/booted-system/nixos-version")"
-      my_hash_string="$(readlink -f "/run/booted-system" | grep -Eo '\b[0-9a-df-np-sv-z]{32}\b')"
-      echo "nixos_booted_system{version=\"$my_version_string\", hash=\"$my_hash_string\"} 1" > /run/prometheus-textfile-exports/booted_system.prom
+      my_hash_string="$(readlink -f "/run/booted-system" | ${pkgs.gnugrep}/bin/grep -Eo '\b[0-9a-df-np-sv-z]{32}\b')"
+      my_specialisation="$(cat "/run/booted-system/specialisation-name" 2>/dev/null || true)"
+      echo "nixos_booted_system{version=\"$my_version_string\", hash=\"$my_hash_string\", specialisation=\"$my_specialisation\"} 1" > /run/prometheus-textfile-exports/booted_system.prom
+    '';
+    system.extraSystemBuilderCmds = lib.mkAfter ''
+      echo "${if config.my.specialisationName == null then "" else config.my.specialisationName}" > $out/specialisation-name
     '';
 
-    system.nixos.tags = lib.mkBefore [
+    system.nixos.tags = lib.mkBefore ([
       depot.version
-    ];
+    ] ++ lib.optional (config.my.specialisationName != null) "specialisation-${config.my.specialisationName}");
 
     services.nginx = {
       recommendedTlsSettings = true;
diff --git a/ops/nixos/lib/rebuilder.nix b/ops/nixos/lib/rebuilder.nix
index ed96b0ffbb..2fae18129d 100644
--- a/ops/nixos/lib/rebuilder.nix
+++ b/ops/nixos/lib/rebuilder.nix
@@ -14,7 +14,14 @@ pkgs.writeShellScriptBin "rebuilder" ''
   export AWS_ACCESS_KEY_ID="${depot.ops.secrets.nixCache.AWS_ACCESS_KEY_ID}"
   export AWS_SECRET_ACCESS_KEY="${depot.ops.secrets.nixCache.AWS_SECRET_ACCESS_KEY}"
 
+  current_specialisation="$(cat /run/current-system/specialisation-name 2>/dev/null)"
+  specialisation_path=""
+  if [[ ! -z "$current_specialisation" ]]; then
+    specialisation_path="specialisation/$current_specialisation/"
+  fi
+
   system="$(nix-build --option substituters "https://cache.nixos.org s3://lukegb-nix-cache?endpoint=storage.googleapis.com&trusted=1" -E "(import $DEPOT_PATH {}).ops.nixos.${system}" --no-out-link)"
   nix-env -p /nix/var/nix/profiles/system --set "$system"
-  "$system/bin/switch-to-configuration" switch
-''
\ No newline at end of file
+  "$system/''${specialisation_path}bin/switch-to-configuration" test
+  "$system/bin/switch-to-configuration" boot
+''
diff --git a/ops/nixos/porcorosso/default.nix b/ops/nixos/porcorosso/default.nix
index ad15246ab0..033ff29a2e 100644
--- a/ops/nixos/porcorosso/default.nix
+++ b/ops/nixos/porcorosso/default.nix
@@ -161,6 +161,7 @@ in {
   services.xserver.windowManager.i3.enable = true;
   services.xserver.videoDrivers = [ "nvidia" ];
   specialisation.intelGraphics.configuration = {
+    my.specialisationName = "intelGraphics";
     services.xserver.videoDrivers = lib.mkForce [ "intel" ];
   };
   services.xserver.displayManager.gdm = {