Step 1: Identify High CPU Processes with top

The top command provides a real-time overview of running processes.

Run:    top -o %CPU

You’ll see a list of running processes sorted by CPU consumption, with details like process ID (PID), user, memory usage, and execution time. Press 1 to view per-core CPU usage. Press q to exit.

Step 2: Get a Detailed View with ps

To list all processes consuming CPU along with their command lines, use:

ps aux –sort=-%cpu | head -10

This output displays:

Step 3: Check CPU Usage History with sar

To analyze CPU usage trends over time, install sysstat:

sudo apt install sysstat

Then run:  sar -u 5 10

This captures CPU usage every 5 seconds for 10 intervals:

A sudden increase in %system or %iowait might indicate a background process or disk-related issue.

Step 4: Find and Stop Rogue Processes

Once you’ve identified a problematic process, kill it with:

sudo kill -9 PID

Example: sudo kill -9 12345

If the process restarts, check if it’s running as a system service:

systemctl status <service-name>

Disable it if necessary:

Step 5: Prevent High CPU Usage in the Future

If a specific app is consuming excessive CPU, limit its resources using cpulimit:

This restricts Firefox to 50% CPU usage.