Troubleshooting

15 articles
Interview Preparation Beginner

Linux Logs

Where Linux logs live — the systemd journal vs /var/log, log rotation with logrotate, and practical log-reading commands for incident …

Jan 20, 2026 Read more
Interview Preparation Intermediate

DNS Resolution Failures

A runbook for diagnosing DNS resolution problems on Linux — resolver configuration, the /etc/hosts override trap, and telling a DNS issue …

Jan 20, 2026 Read more
Interview Preparation Intermediate

High Load Average

A runbook for interpreting and diagnosing a high Linux load average — and why it doesn't automatically mean a CPU problem.

Jan 20, 2026 Read more
Interview Preparation Intermediate

Zombie & Defunct Processes

A runbook for diagnosing zombie (defunct) processes on Linux — why they accumulate, why kill -9 doesn't work on them, and how to actually …

Jan 20, 2026 Read more
Interview Preparation Intermediate

Permission Denied Errors

A runbook for diagnosing 'Permission denied' errors on Linux — file permissions, ownership, directory traversal permissions, ACLs, and …

Jan 20, 2026 Read more
Interview Preparation Advanced

Network Connectivity Issues

A layered runbook for diagnosing 'can't connect' problems on Linux — working outward from the local interface through routing, DNS, …

Jan 20, 2026 Read more
Interview Preparation Intermediate

Service Won't Start

A systemd runbook for diagnosing why a service fails to start — reading journalctl and systemctl status correctly, and the most common root …

Jan 20, 2026 Read more
Interview Preparation Advanced

Slow Disk I/O

A runbook for diagnosing storage-bound performance problems on Linux — reading iostat correctly and telling apart a slow disk from a slow …

Jan 20, 2026 Read more
Interview Preparation Intermediate

Disk Full — No Space Left on Device

A runbook for diagnosing and recovering from a full disk on Linux, including the inode-exhaustion and deleted-but-open-file variants that df …

Jan 20, 2026 Read more
Interview Preparation Advanced

High Memory Usage & OOM Kills

A runbook for diagnosing memory pressure and OOM killer events on Linux — reading free correctly, finding the memory hog, and confirming a …

Jan 20, 2026 Read more
Interview Preparation Advanced

High CPU Usage

A runbook for diagnosing sustained high CPU usage on a Linux server — from identifying the offending process down to the exact thread and …

Jan 20, 2026 Read more