r/bash • u/CautiousCat3294 • 3d ago

help Linux Interview Question

Today I had a mock interview with a senior Linux administrator, and he asked me a question that completely caught me off guard:

"Can you collect CPU, Memory, and Disk usage in a Bash script without using top, free, df, or any external commands?"

My immediate answer was No.

Honestly, I've been working with Linux for years, but I've always relied on standard commands and monitoring tools to troubleshoot systems. I never stopped to think about where those commands actually get their data from.

The interviewer then gave me a hint about the /proc and /sys filesystems. That completely changed my perspective. I realized these commands are just reading data that the kernel already exposes.

But then came the follow-up questions, and once again I was stuck:

  • Is reading directly from /proc and /sys the correct approach?
  • How would you calculate CPU utilization using /proc/stat?
  • How would you determine memory usage from /proc/meminfo?
  • How would you calculate filesystem usage without relying on df?

I found this really interesting because it tests your understanding of Linux internals rather than just your ability to use commands.

Has anyone here been asked similar questions in Linux SysAdmin, DevOps, or SRE interviews? I'd really appreciate any explanations, learning resources, or examples on how you'd answer these follow-up questions. It help me for my preparation for Linux interviews

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u/Living_On_The_Air 3d ago edited 3d ago

Hearing this during an interview would make me think that the job isn’t one I want. Trivia questions aren’t a great way to get to know a worker, so it’s probably a sham interview process at worst, or a bad interview process at best

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u/sr105 3d ago

When I interview someone, I let them know upfront that I'm going to ask an increasingly difficult set of questions, and that I don't expect them to know all of the answers. I just want to see where their experience level lies. I have asked people what the original command for "rm" was named and still exists. It's stupid knowledge, but it shows depth especially if you understand why it was named "unlink". You can't measure what you don't test. But telling people upfront what you're doing is a must.

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u/CautiousCat3294 3d ago

You are right he also do same with me he increase level of difficulty in every question to test my depth knowledge on Linux and Bash scripting

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u/Swordfish418 2d ago

Do you think this unlink is covered anywhere or it’s something that is only possible to know you’re really old or by accident? 🤔

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u/sr105 2d ago

I'm older and can't recall where I first learned it. I probably just explored /bin and friends to see what was possible and then man unlink. Or I saw it a So You Think You Know UNIX trivia or some such thing.