Use lsb_release for distro detection.

stack.sh

@@ -22,7 +22,9 @@
 
 # Warn users who aren't on natty, but allow them to override check and attempt
 # installation with ``FORCE=yes ./stack``
-if ! egrep -q 'natty|oneiric' /etc/lsb-release; then
+DISTRO=$(lsb_release -c -s)
+
+if [[ ! ${DISTRO} =~ (natty|oneiric) ]]; then
     echo "WARNING: this script has only been tested on natty and oneiric"
     if [[ "$FORCE" != "yes" ]]; then
         echo "If you wish to run this script anyway run with FORCE=yes"