* When runtime switching to a new configuration, stop/start/restart

Upstart jobs as appropriate.  I.e., if a job exists in the old but
  not the new configuration, stop it; if it exists in the new but not
  the old, start it; and most interesting, if it exists in both but
  its store paths differ, restart it.  So the purely functional model
  combined cryptographic hashing allows us to precisely identify how
  two configurations differ from each other 

svn path=/nixos/trunk/; revision=7385

configuration/switch-to-configuration.sh

@@ -2,7 +2,7 @@
 
 set -e
 export PATH=/empty
-for i in @path@; do PATH=$PATH:$i/bin; done
+for i in @path@; do PATH=$PATH:$i/bin:$i/sbin; done
 action="$1"
 
 if ! test -e /etc/NIXOS; then
@@ -34,9 +34,44 @@ if test "$action" = "switch" -o "$action" = "boot"; then
 fi
 
 if test "$action" = "switch" -o "$action" = "test"; then
+
+    oldEvents=$(readlink -f /etc/event.d || true)
+    newEvents=$(readlink -f @out@/etc/event.d)
+
+    echo "old: $oldEvents"
+    echo "new: $newEvents"
+
+    # Stop all services that are not in the new Upstart
+    # configuration.
+    for event in $(cd $oldEvents && ls); do
+        if ! test -e "$newEvents/$event"; then
+            echo "stopping $event..."
+            initctl stop "$event"
+        fi
+    done
+
+    # Activate the new configuration (i.e., update /etc, make
+    # accounts, and so on).
     echo "Activating the configuration..."
     @out@/activate
-    kill -TERM 1 # make Upstart reload its events    
+
+    # Make Upstart reload its events.  !!! Should wait until it has
+    # finished processing its stop events.
+    kill -TERM 1 
+
+    # Start all new services and restart all changed services.
+    for event in $(cd $newEvents && ls); do
+        if ! test -e "$oldEvents/$event"; then
+            echo "starting $event..."
+            initctl start "$event"
+        elif test "$(readlink "$oldEvents/$event")" != "$(readlink "$newEvents/$event")"; then
+            echo "restarting $event..."
+            initctl stop "$event"
+            initctl start "$event"
+        else
+            echo "unchanged $event"
+        fi
+    done
 fi
 
 sync

configuration/system.nix

@@ -242,7 +242,14 @@ rec {
     kernel = pkgs.kernel + "/vmlinuz";
     initrd = initialRamdisk + "/initrd";
     # Most of these are needed by grub-install.
-    path = [pkgs.coreutils pkgs.gnused pkgs.gnugrep pkgs.findutils pkgs.diffutils];
+    path = [
+      pkgs.coreutils
+      pkgs.gnused
+      pkgs.gnugrep
+      pkgs.findutils
+      pkgs.diffutils
+      pkgs.upstart # for initctl
+    ];
   };