What could be the next step after 4 years as a Unix support engineer?
Your biggest weapon is command line. If you are proficient in the command line interface, some shell scripting, and understand sed, awk, grep etc. You can easily start with IT automation tools like Ansible, Chef, Apache Maven. A year later learn DevOps, cloud deployment tools, cloud-native If you are good at coding ( i assume you write some unix shell script) you can learn python or R and get into data science I started my career as a UNIX engineer two decades earlier and my scripting and command line knowledge still make me do wonders when others are clicking and moving from one screen to another using GUI. It certainly helps you debug better and faster in many contexts of todays IT deployment and data science tools