add drive compact/zero

prepare-ubuntu-18.04-template.sh

@@ -98,6 +98,11 @@ sudo sed -ri '/\sswap\s/s/^#?/#/' /etc/fstab
 # cleans out all of the cloud-init cache / logs - this is mainly cleaning out networking info
 sudo cloud-init clean --logs
 
+echo "Compacting drive..."
+dd if=/dev/zero of=EMPTY bs=1M > /dev/null
+rm -vf /root/EMPTY
+fstrim -av
+
 #cleanup shell history
 cat /dev/null > ~/.bash_history && history -c
 history -w