DevOps and cloud

Stage 2 · Lesson 8 of 8

Debugging with dig, curl, ss and traceroute

Networking for engineers

Most networking problems give way to four tools, used in order. dig example.com +short shows what a name resolves to. dig @8.8.8.8 example.com asks a public resolver, so you can compare answers.

curl -v shows whether you can connect, what happened during the handshake and what the server sent back. On the server, ss -ltnp shows what is actually listening, and on which address. Finally, (or mtr) shows where along the path stop.

Work from the bottom up. Does the name resolve? Is the port reachable?

Is anything listening? What does the app answer? This stage's skills come together here, and you will use the same order inside containers and later.

Common trapjumping straight to the app's code when the problem is a or a closed port.

A question to check yourself, an AI practice session and 1 cheat sheet entry come with the full roadmap. Unlock

Resources for this stage

Start with

Practise

  • DevOps Exercises

    Answer its networking questions before reading the answers to find your gaps

Keep handy

  • NGINX Beginner's Guide

    Official guide to serving files and proxying to an app, the base of every config

  • MDN Web Docs

    The HTTP guides on headers, caching and status codes, for debugging proxies

Also worth your time

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