System hangs when running nodes

[sumitbadaya]

Below is the configuration of my system on which am trying to run Cordapp:
RAM: 8 GB
OS: Ubuntu 18.04.1 LTS
Processor: Intel® Core™ i3-3220 CPU @ 3.30GHz × 4
Graphics: Intel® Ivybridge Desktop
OS Type: 64-bit

I am following the steps to run Cordapp from Below:
Cordapp Java Template

My computer system hangs when I try to run below command.

./runnodes

What is the recommended system requirement to run a Cordapp?
If my system should be fine running a Cordapp, then what might be getting wrong which is hanging my system?

Please help as am new to Cordapp and running it for very first time.