Hardening (#30)

* set build-argument for environment

* hardening remove dangerous commands

* add hardening scripts for base and final image

app/hardening_base.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+rm -fr /var/spool/cron
+rm -fr /etc/crontabs
+rm -fr /etc/periodic
+
+# Remove every user and group but root
+sed -i -r '/^(root)/!d' /etc/group
+sed -i -r '/^(root)/!d' /etc/passwd    
+
+# Remove init scripts since we do not use them.
+rm -fr /etc/inittab
+
+# Remove kernel tunables since we do not need them.
+rm -fr /etc/sysctl*
+rm -fr /etc/modprobe.d
+
+# Remove fstab since we do not need it.
+rm -f /etc/fstab