Chapter 4 · System Maintenance and Operations·v1.0.0·Updated 7/7/2026·~11 min
What's changed: Initial version (topic 2.04, subtopics 2.04.1–2.04.6)
4.5Availability Monitoring, Resource Monitoring, and Operations Tools
Key points
Learn the concepts behind detecting resource exhaustion, overload, and abnormal termination early: the behavior of the OOM killer, remote monitoring via SNMP, designing thresholds and alerts, and representative monitoring tools (Icinga2, Nagios, collectd, MRTG, Cacti, Zabbix).
Checking the current state with individual commands cannot catch failures that happen overnight or on weekends. Building continuous watchers that alert when thresholds are crossed is the foundation that keeps a 24/7 service running.
4.5.1What to watch for, and the OOM killer
- Anomalies to catch early: resource exhaustion (memory, disk running out), overload (sustained high CPU/traffic), and abnormal termination (process/service crashes).
- The OOM killer (Out-Of-Memory Killer) is the kernel mechanism that, when physical memory and swap are nearly exhausted, forcibly selects and terminates a process. It is the first suspect when investigating an unexpected process termination.
4.5.2SNMP, thresholds, and representative tools
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