Linux & Networking Questions
Part of the DevOps Roadmap
In short
'A server is at 100% CPU, what do you do?' and 'What happens when you type a URL?' come up in nearly every DevOps interview. They want to see you think in commands, not definitions.
'How would you troubleshoot a server with high CPU usage?' or 'explain what happens when you type a URL into a browser' — testing genuine command-line and networking fluency from Phases 2-3.
Think of it like this
The driving test at the RTO
At the driving test nobody asks you to recite traffic rules. They make you ride the figure eight without putting a foot down. Linux and networking rounds are the same: the interviewer wants to watch you actually work through the problem, one command at a time.
Watch it happen
What happens when you open https://shop.in
1/6The browser and OS check their own DNS caches first. If the answer is there, DNS is skipped.
The big ideas
What you need to know
Know your first commands
top or htop, ps, free -h, df -h, ss -tulpn, journalctl. Say why you're running each one.
Load average
Load is roughly the number of tasks running or waiting. Compare it to CPU cores: load 8 on 8 cores is busy, on 2 it's overloaded.
Layers help you debug
Work bottom up: is DNS right, is the port open, does TLS work, what does HTTP return.
Think out loud
Interviewers grade your process. Say what you're checking and what each result rules out.
See it in code
Walk through the code
1# High CPU: who is using it?2uptime # load averages for 1, 5, 15 min3top -o %CPU # live view sorted by CPU (Linux procps)4ps aux --sort=-%cpu | head # top CPU processes, one snapshot5 6# Is it really CPU, or waiting on disk?7vmstat 1 5 # 'wa' column = time waiting on I/O8 9# Networking basics10dig +short shop.in # what IP does DNS return?11ss -tulpn # which ports are listening, by which process12curl -v https://shop.in # DNS, TCP, TLS and HTTP in one go1/3Start broad with load, then find the exact process eating CPU.
In interviews, explain the output you expect. 'If wa is high, it's disk, not CPU' is the kind of line that impresses.
Save yourself the pain
Common mistakes
Oops
Jumping straight to 'I'd restart the server'.
Do this instead
Gather facts first: which process, since when, what changed. Restarting can hide the cause and it will come back.
Oops
Reciting the OSI model when asked about a slow website.
Do this instead
Use layers as a checklist, but answer with real steps and commands for each one.
Your mission
Run a mock round on yourself
Quick check
A 4-core server shows load average 12 but CPU usage is low. What's the likely cause?
Go deeper
- 1Review Phases 2-3 and practice explaining each concept without notes.
- 2Practice a live troubleshooting scenario using ps, top, and networking tools.
- 3Prepare to walk through the full DNS-to-response flow for a web request.
More systems & infrastructure at this stop
Kubernetes & Container Questions
Cloud Architecture Questions
Stuck on this topic? Ask an Insider
Get 1:1 guidance from people who've walked this exact path — on the InsideEdge app.
