TCS Linux, Networking & Scripting interview questions

Ordering and retransmission are what TCP adds, and both of them cost time. Naming something that deliberately gives them up, and saying why, is what turns a textbook answer into a real one.

Five stages, and which one you are stuck in tells you what to fix. A machine that reaches a GRUB prompt has a different problem from one that hangs waiting on a filesystem that no longer exists.

Most of what looks like used memory on a healthy Linux box is page cache doing its job. Knowing which column to read, and why df and du disagree, is half of Linux triage.

The oldest question in systems interviewing and still the best, because it is unbounded: every layer you can describe is another layer you could debug.

Two different resources produce the same errno, and the second one is invisible unless you know to look. One command distinguishes them.

The scripting round in disguise. The constraint is the question: it exists to see whether you stream or whether you load, and everything else is about whether the script is safe to run twice.

A beginner question with a senior follow-up hiding in it. Once you know a hard link is a second name for an inode, log rotation and backup behaviour both stop being mysterious.

Everyone recites the four letters. The scoring answer walks each packet across the wire and knows the places the exchange silently dies.

A one-line mistake that locks you out of the obvious fix. The fast recovery teaches more about the permission model than any man page will.

Every ops engineer schedules jobs; few can say which shell cron uses, where stdout lands, or why percent signs delete half a command. Those gaps are exactly what interviews test.

The answer that lands is about one epoll loop per core, not config snippets. Master versus worker duties, the arithmetic of worker_connections, and the limits people forget to raise.

Volatile by default on many distros, size-capped by silent policy, binary on disk. Know the storage modes, the vacuum knobs, and how journald feeds central logging.

VRRP heartbeats, market data feeds, mDNS noise and cluster chatter all ride multicast, and all of it assumes a switched LAN. Why clouds drop it and what replaces it.

The question that separates people who have debugged a hung rollout from people who have read about one. The interesting half is not the signal, it is PID 1.

A staple of every networking round, and the follow-up is always about TLS termination. Knowing which layer sees what decides most of the answer.

The classic ephemeral port exhaustion question. TIME_WAIT is a familiar phrase and the useful facts are narrower: which side accumulates it, and why the popular fix is dangerous.

The arithmetic takes thirty seconds to learn and gets asked constantly. What it is really testing is whether you have ever had to size a VPC that could not be resized later.

Interviewers use this to sort memorised trivia from people who have chased a slow lookup. Three roles, one bit, and the caching rules most candidates repeat incorrectly.

A growing backlog of sockets waiting for the application to close its side usually points at lifecycle handling. Here is the hunt from ss output to the pool timeout that caused it.