Lesson 0: Why Understand the System and the Network at All?
Your website works perfectly on your laptop — and then users report it's completely unreachable. There's no error message in the code, no stack trace to look at. This isn't a bug in a function you wrote — it's a failure in the layer beneath the code: how the system runs your service, and how machine
When something breaks on a server, code alone won't tell you why — you need to look under the hood, at the system and the network.
- Production incident
- An event where a live service stops working or slows down for real users — not just a failure in a development environment.
- Root cause
- The actual reason a failure occurred, as opposed to the external symptom you notice first.
- OS internals
- How the kernel manages processes, memory, and files beneath every program running on the machine.
- Network reachability
- Whether one machine can reach another over the network at all, before you even discuss what runs on it.
- Systems-level debugging
- Diagnosing failures using tools that reveal what actually happens in the kernel and the network, not just in application code.
