diff --git a/modules/nix/default.nix b/modules/nix/default.nix
index 9bf3e0d..81e0ab9 100644
--- a/modules/nix/default.nix
+++ b/modules/nix/default.nix
@@ -16,31 +16,33 @@ let
       sh = pkgs.stdenv.shell;
       binshDeps = pkgs.writeReferencesToFile sh;
     in
-      pkgs.runCommand "nix.conf" { extraOptions = cfg.extraOptions; } ''
-        cat > $out <<END
-        # WARNING: this file is generated from the nix.* options in
-        # your NixOS configuration, typically
-        # /etc/nixos/configuration.nix.  Do not edit it!
-        ${optionalString config.services.nix-daemon.enable ''
-          build-users-group = nixbld
-        ''}
-        build-max-jobs = ${toString cfg.maxJobs}
-        build-cores = ${toString cfg.buildCores}
-        build-use-sandbox = ${if (builtins.isBool cfg.useSandbox) then (if cfg.useSandbox then "true" else "false") else cfg.useSandbox}
-        ${optionalString (cfg.sandboxPaths != []) ''
-          build-sandbox-paths = ${toString cfg.sandboxPaths}
-        ''}
-        binary-caches = ${toString cfg.binaryCaches}
-        trusted-binary-caches = ${toString cfg.trustedBinaryCaches}
-        binary-cache-public-keys = ${toString cfg.binaryCachePublicKeys}
-        ${optionalString cfg.requireSignedBinaryCaches ''
-          signed-binary-caches = *
-        ''}
-        trusted-users = ${toString cfg.trustedUsers}
-        allowed-users = ${toString cfg.allowedUsers}
-        $extraOptions
-        END
-      '';
+      pkgs.runCommandNoCC "nix.conf"
+        { preferLocalBuild = true; extraOptions = cfg.extraOptions; }
+        ''
+          cat > $out <<END
+          # WARNING: this file is generated from the nix.* options in
+          # your NixOS configuration, typically
+          # /etc/nixos/configuration.nix.  Do not edit it!
+          ${optionalString config.services.nix-daemon.enable ''
+            build-users-group = nixbld
+          ''}
+          build-max-jobs = ${toString cfg.maxJobs}
+          build-cores = ${toString cfg.buildCores}
+          build-use-sandbox = ${if (builtins.isBool cfg.useSandbox) then (if cfg.useSandbox then "true" else "false") else cfg.useSandbox}
+          ${optionalString (cfg.sandboxPaths != []) ''
+            build-sandbox-paths = ${toString cfg.sandboxPaths}
+          ''}
+          binary-caches = ${toString cfg.binaryCaches}
+          trusted-binary-caches = ${toString cfg.trustedBinaryCaches}
+          binary-cache-public-keys = ${toString cfg.binaryCachePublicKeys}
+          ${optionalString cfg.requireSignedBinaryCaches ''
+            signed-binary-caches = *
+          ''}
+          trusted-users = ${toString cfg.trustedUsers}
+          allowed-users = ${toString cfg.allowedUsers}
+          $extraOptions
+          END
+        '';
 in
 
 {
diff --git a/modules/system/etc.nix b/modules/system/etc.nix
index b3d803a..6577aec 100644
--- a/modules/system/etc.nix
+++ b/modules/system/etc.nix
@@ -31,12 +31,14 @@ in
 
   config = {
 
-    system.build.etc = pkgs.runCommand "etc" {} ''
-      mkdir -p $out/etc
-      cd $out/etc
-      ${concatMapStringsSep "\n" (attr: "mkdir -p $(dirname '${attr.target}')") etc}
-      ${concatMapStringsSep "\n" (attr: "ln -s '${attr.source}' '${attr.target}'") etc}
-    '';
+    system.build.etc = pkgs.runCommandNoCC "etc"
+      { preferLocalBuild = true; }
+      ''
+        mkdir -p $out/etc
+        cd $out/etc
+        ${concatMapStringsSep "\n" (attr: "mkdir -p $(dirname '${attr.target}')") etc}
+        ${concatMapStringsSep "\n" (attr: "ln -s '${attr.source}' '${attr.target}'") etc}
+      '';
 
     system.activationScripts.etc.text = ''
       # Set up the statically computed bits of /etc.
diff --git a/modules/system/launchd.nix b/modules/system/launchd.nix
index 5e5b262..dce0523 100644
--- a/modules/system/launchd.nix
+++ b/modules/system/launchd.nix
@@ -84,15 +84,17 @@ in
 
   config = {
 
-    system.build.launchd = pkgs.runCommand "launchd" {} ''
-      mkdir -p $out/Library/LaunchAgents $out/Library/LaunchDaemons $out/user/Library/LaunchAgents
-      cd $out/Library/LaunchAgents
-      ${concatMapStringsSep "\n" (attr: "ln -s '${attr.source}' '${attr.target}'") launchAgents}
-      cd $out/Library/LaunchDaemons
-      ${concatMapStringsSep "\n" (attr: "ln -s '${attr.source}' '${attr.target}'") launchDaemons}
-      cd $out/user/Library/LaunchAgents
-      ${concatMapStringsSep "\n" (attr: "ln -s '${attr.source}' '${attr.target}'") userLaunchAgents}
-    '';
+    system.build.launchd = pkgs.runCommandNoCC "launchd"
+      { preferLocalBuild = true; }
+      ''
+        mkdir -p $out/Library/LaunchAgents $out/Library/LaunchDaemons $out/user/Library/LaunchAgents
+        cd $out/Library/LaunchAgents
+        ${concatMapStringsSep "\n" (attr: "ln -s '${attr.source}' '${attr.target}'") launchAgents}
+        cd $out/Library/LaunchDaemons
+        ${concatMapStringsSep "\n" (attr: "ln -s '${attr.source}' '${attr.target}'") launchDaemons}
+        cd $out/user/Library/LaunchAgents
+        ${concatMapStringsSep "\n" (attr: "ln -s '${attr.source}' '${attr.target}'") userLaunchAgents}
+      '';
 
     system.activationScripts.launchd.text = ''
       # Set up launchd services in /Library/LaunchAgents and /Library/LaunchDaemons