Essential Linux Skills for IT Operations

Filesystem navigation and the directories that matter

In operations you rarely need the whole filesystem — you need to know where things live. /var/log is where most logs sit, /etc is where services are configured, /proc and /sys expose kernel and process state, /home and /root hold user data. Be fluent with ls, cd, pwd, find and locate. The single command that pays off most in production is find with time filters, because "what changed in the last hour" is a constant question.

find /etc /var/log -type f -mmin -60 2>/dev/null

Processes and services

When a service misbehaves, you need to see its processes and control it. Use ps aux and top or htop to list and watch processes; systemctl status, systemctl restart and journalctl -u to inspect and manage systemd services. Knowing how to read a service status — active (running), failed, activating — and how to follow its logs with journalctl -u <service> -f is the difference between guessing and diagnosing. This is core daily work for a Production Engineer.

systemctl status nginx
journalctl -u nginx -f

Logs: reading and filtering

Logs are where the answer usually hides. Learn to search them efficiently: grep for keywords, grep -i for case-insensitive, tail -f to follow a file live, and combine with awk or cut to extract fields. For structured logs, journalctl --since and -u filter by time and unit. The reflex to look at the timestamps around an alert — not just the error line — is what a Monitoring Specialist does all day.

journalctl --since "30 min ago" -p err
# or, in a plain log file:
grep -i "error" /var/log/app.log | tail -n 50

Disk, memory and CPU inspection

The three resources that run out. Use df -h to see filesystem usage and du -sh to find what is eating a directory; free -h for memory and swap; top, htop or pidstat for CPU and per-process usage. A full disk is one of the most common production incidents, so know how to find big files and old logs fast. Memory is trickier: Linux caches aggressively, so "used" memory is not always a problem — learn to read the available column and the cache/buffer split.

df -h
du -sh /var/* | sort -h
find /var -type f -size +500M 2>/dev/null

Networking diagnostics

Operations is half networking. Know ping and traceroute for reachability and path, ss or netstat for listening ports and connections, dig or nslookup for DNS, curl -I for a quick HTTP check, and ip a / ip r for addresses and routes. When a service is "down", the first question is often whether it is down or unreachable — these commands answer that. A NOC Analyst lives in this toolkit.

ping -c 4 8.8.8.8
dig +short myapp.example.com
curl -I https://myapp.example.com
ss -tlnp | grep :443

Permissions and basic shell usage

Understand the permission triplet (owner, group, others) and read/write/execute, how to change it with chmod and chown, and why a service cannot read its config file is often a permission problem. Know sudo, how to switch user with su -, and enough shell scripting (variables, pipes, redirects, a simple for loop) to chain commands. You do not need to write large scripts to start — but you must be able to read one and adjust it. This is the on-ramp to the automation expected of a DevOps Engineer.

A troubleshooting methodology for Linux incidents

• Define the symptom precisely: which service, which host, since when.
• Check the four resources first: disk, memory, CPU, network.
• Look at the service status and its recent logs around the alert time.
• Check recent changes: deployments, config edits, package updates.
• Form a hypothesis, test the cheapest fix, and confirm before closing.

Where to go from here

These skills compound: the same Linux reflexes that make you useful as a Monitoring Specialist or NOC Analyst are the foundation for Linux System Administrator and eventually DevOps Engineer. When you want to prove the level on paper, our Best Certifications for IT Operations Careers guide explains which Linux and operations certifications are worth the investment. To see how these skills are tested in interviews, read Monitoring Specialist Interview Questions & Answers and NOC Analyst Interview Questions & Preparation Guide.