Add support for shutdown scripts

These can be added by other packages if they need to do something on
clean shutdown.

Crash only software can ignore this.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

pkg/init/bin/rc.init

@@ -119,7 +119,7 @@ ulimit -n 1048576
 ulimit -p unlimited
 
 # execute other init processes
-INITS="$(find /etc/init.d -type f | sort)"
+INITS="$(find /etc/init.d -type f 2>/dev/null | sort)"
 for f in $INITS
 do
 	$f

pkg/init/bin/rc.shutdown

@@ -1,13 +1,20 @@
 #!/bin/sh
 
-[ "$1" = "reboot" ] && exec /sbin/reboot
-
-# poweroff
+# execute other shutdown processes
+SHUTS="$(find /etc/shutdown.d -type f 2>/dev/null | sort)"
+for f in $SHUTS
+do
+        $f
+done
 
+# kill all processes and unmount filesystems
 /usr/sbin/killall5 -15
 /bin/sleep 5
 /usr/sbin/killall5 -9
 /sbin/swapoff -a
 /bin/echo "Unmounting filesystems"
 /bin/umount -a -r
+
+# shutdown or reboot
+[ "$1" = "reboot" ] && exec /sbin/reboot -f
 /sbin/poweroff -f