nix-daemon: Restart when nix.conf changes

modules/services/misc/nix-daemon.nix

@@ -20,6 +20,31 @@ let
       extraGroups = [ "nixbld" ];
     };
 
+  nixConf =
+    let
+      # Tricky: if we're using a chroot for builds, then we need
+      # /bin/sh in the chroot (our own compromise to purity).
+      # However, since /bin/sh is a symlink to some path in the
+      # Nix store, which furthermore has runtime dependencies on
+      # other paths in the store, we need the closure of /bin/sh
+      # in `build-chroot-dirs' - otherwise any builder that uses
+      # /bin/sh won't work.
+      binshDeps = pkgs.writeReferencesToFile config.system.build.binsh;
+    in
+      pkgs.runCommand "nix.conf" {extraOptions = cfg.extraOptions; } ''
+        extraPaths=$(for i in $(cat ${binshDeps}); do if test -d $i; then echo $i; fi; done)
+        cat > $out <<END
+        # WARNING: this file is generated.
+        build-users-group = nixbld
+        build-max-jobs = ${toString (cfg.maxJobs)}
+        build-use-chroot = ${if cfg.useChroot then "true" else "false"}
+        build-chroot-dirs = ${toString cfg.chrootDirs} $(echo $extraPaths)
+        binary-caches = ${toString cfg.binaryCaches}
+        trusted-binary-caches = ${toString cfg.trustedBinaryCaches}
+        $extraOptions
+        END
+      '';
+
 in
 
 {
@@ -226,48 +251,20 @@ in
 
     nix.chrootDirs = [ "/dev" "/dev/pts" "/proc" "/bin" ];
 
-    environment.etc =
+    environment.etc."nix/nix.conf".source = nixConf;
-      [ { # Nix configuration.
-          source =
-            let
-              # Tricky: if we're using a chroot for builds, then we need
-              # /bin/sh in the chroot (our own compromise to purity).
-              # However, since /bin/sh is a symlink to some path in the
-              # Nix store, which furthermore has runtime dependencies on
-              # other paths in the store, we need the closure of /bin/sh
-              # in `build-chroot-dirs' - otherwise any builder that uses
-              # /bin/sh won't work.
-              binshDeps = pkgs.writeReferencesToFile config.system.build.binsh;
-            in
-              pkgs.runCommand "nix.conf" {extraOptions = cfg.extraOptions; } ''
-                extraPaths=$(for i in $(cat ${binshDeps}); do if test -d $i; then echo $i; fi; done)
-                cat > $out <<END
-                # WARNING: this file is generated.
-                build-users-group = nixbld
-                build-max-jobs = ${toString (cfg.maxJobs)}
-                build-use-chroot = ${if cfg.useChroot then "true" else "false"}
-                build-chroot-dirs = ${toString cfg.chrootDirs} $(echo $extraPaths)
-                binary-caches = ${toString cfg.binaryCaches}
-                trusted-binary-caches = ${toString cfg.trustedBinaryCaches}
-                $extraOptions
-                END
-              '';
-          target = "nix/nix.conf";
-        }
-      ]
 
-      ++ optional (cfg.distributedBuilds && !cfg.manualNixMachines)
+    # List of machines for distributed Nix builds in the format
-        { # List of machines for distributed Nix builds in the format expected
+    # expected by build-remote.pl.
-          # by build-remote.pl.
+    environment.etc."nix.machines" =
-          source = pkgs.writeText "nix.machines"
+      { enable = cfg.distributedBuilds && !cfg.manualNixMachines;
-            (concatStrings (map (machine:
+        text =
+          concatMapStrings (machine:
             "${machine.sshUser}@${machine.hostName} "
             + (if machine ? system then machine.system else concatStringsSep "," machine.systems)
             + " ${machine.sshKey} ${toString machine.maxJobs} "
             + (if machine ? speedFactor then toString machine.speedFactor else "1" )
             + "\n"
-            ) cfg.buildMachines));
+          ) cfg.buildMachines;
-          target = "nix.machines";
       };
 
     systemd.sockets."nix-daemon" =
@@ -292,6 +289,8 @@ in
             IOSchedulingPriority = cfg.daemonIONiceLevel;
             LimitNOFILE = 4096;
           };
+
+        restartTriggers = [ nixConf ];
       };
 
     nix.envVars =