High CPU usage on a Linux web server is one of those problems that invites bad guesses. People blame the host, restart random services and hope the issue disappears. Sometimes it does. More often it comes back because the real cause was never identified.
This guide explains how to diagnose high CPU usage on a Linux web server methodically.
See what is actually using the CPU
Start with tools such as top, htop and ps to identify which process is consuming resources. That tells you whether the issue is the web server, database, PHP worker, a cron job or something stranger.
Correlate with logs and traffic
High CPU may come from a traffic spike, bot abuse, slow queries, plugin issues or stuck tasks. Logs help connect the resource spike to real activity.
Check recent changes
New deployments, plugin updates, backup jobs, indexing tasks and scheduled scripts are common causes. Do not treat the incident like it appeared by magic.
Final thoughts
CPU problems become much easier to solve once you stop guessing and start correlating process data with logs and changes. Evidence beats superstition every time.