Linux

The operating system that runs everything except your desktop (probably). Linux is the open-source kernel created by Linus Torvalds in 1991 that now powers over 90% of the world’s servers, all Android phones, most embedded devices, and basically the entire cloud.

In DevOps, Linux is the lingua franca. Your containers run Linux. Your CI runners run Linux. Your production servers run Linux. Even if you develop on a Mac, you deploy to Linux. It’s Linux all the way down.

Why it matters: Understanding Linux is non-negotiable in DevOps. Shell scripting, file permissions, networking, process management — it’s all Linux fundamentals.