@autonomus the problem with the helloworld module is, that is only running in the browser environment, so it doesn’t have access to linux in that sense. What you need is a node_helper which has access to your machine.
A good example is the pir sensor module https://github.com/paviro/MMM-PIR-Sensor/blob/master/node_helper.js#L59 In this line it executes a linux command as a child process.
If you check the documentation you can get the response of it in a callback https://nodejs.org/dist/latest-v10.x/docs/api/child_process.html#child_process_child_process_exec_command_options_callback
If you need more information about node helpers you can check the docs here https://github.com/MichMich/MagicMirror/tree/master/modules#the-node-helper-node_helperjs