Use debhelper for postinst script.

debian/ai-firewall.postinst

 #!/bin/sh
 
-set -e
-
-if [ -x /etc/init.d/ai-firewall ]; then
-    update-rc.d ai-firewall defaults >/dev/null
-
-    if [ -x /usr/sbin/invoke-rc.d ]; then
-        invoke-rc.d ai-firewall restart
-    else
-        /etc/init.d/ai-firewall restart
-    fi
-fi
-
 #DEBHELPER#
 
 exit 0

debian/changelog

+ai-firewall (0.1-2) unstable; urgency=low
+
+  * Use debhelper for postinst script.
+
+ -- Autistici/Inventati <debian@autistici.org>  Sun, 22 Jun 2014 19:12:21 +0000
+
 ai-firewall (0.1-1) unstable; urgency=low
 
   * Update debian package to start service at boot