-build_ok=true
-
-# Check that:
-# * IP forwarding is enabled in the kernel.
-
-if [ "$(/sbin/sysctl --values net.ipv4.ip_forward)" != "1" ]
-then
- echo >&2 "WARNING: IP forwarding must be enabled in the kernel."
- echo >&2 "Try: sudo sysctl net.ipv4.ip_forward=1"
- build_ok=false
-fi
-
-# * Docker can be found in the user's path
-# * The user is in the docker group
-# * cgroup is mounted
-# * the docker daemon is running
-
-if ! docker images > /dev/null 2>&1
+# make sure Ruby 1.9.3 is installed before proceeding
+if ! ruby -e 'exit RUBY_VERSION >= "1.9.3"' 2>/dev/null