Add stage 3

README.md

@@ -61,6 +61,9 @@ maintenance and allows for more easy customization.
    you were looking for something between truly minimal and Raspbian-lite,
    here's where you start trimming.
 
+ - **Stage 3** - secure system. This stage configures SSH do disallow root
+   login, adds iptables rules, etc.
+
 ### Stage specification
 
 If you wish to build up to a specified stage (such as building up to stage 2

stage3/EXPORT_IMAGE

@@ -0,0 +1 @@
+IMG_SUFFIX="-secure"

stage3/prerun.sh

@@ -0,0 +1,4 @@
+#!/bin/bash -e
+if [ ! -d ${ROOTFS_DIR} ]; then
+	copy_previous
+fi