Introduction to Linux Log Analysis: Tools for System Fault Diagnosis

Linux logs are the "system diaries" that record system operation events and anomalies, serving as the core clue for fault diagnosis (e.g., web service failures can be located via logs for 404 errors or connection failures). Core log files include: /var/log/messages (system routine events and errors), /var/log/auth.log (authentication, login, and permission changes), /var/log/dmesg (kernel hardware initialization and driver errors), and application-specific service logs. Commonly used viewing commands are: tail -f for real-time tracking, grep for filtering keywords (e.g., "error"), and cat/less for file processing. Fault diagnosis follows the process: "phenomenon → locate logs → keyword analysis": for user login failure, check auth.log (keyword "Failed password"); for web service startup failure, check service error logs (keyword "port occupied"); for system lag, check messages/dmesg (keywords "out of memory" or "IO error"). Key points to master: selecting the right log, filtering keywords, and paying attention to timestamps. Advanced tools include journalctl and the ELK Stack.