How to Monitor System Load Average Periodically in Linux

Monitoring system performance is a critical task for system administrators and developers. While the top command provides comprehensive resource information, sometimes you need a lighter, more focused approach to track specific metrics over time. This guide demonstrates how to create a simple monitoring loop to periodically check CPU load average and memory usage.

Understanding the Need

When troubleshooting performance issues or monitoring system behavior during specific operations, you may want to:

• Track CPU load trends without the overhead of full system monitoring tools
• Record memory and swap usage at regular intervals
• Create a lightweight monitoring solution that can run in the background
• Capture snapshots of system state for later analysis

The Solution: Using a While Loop

Instead of continuously watching top, we can create a simple loop that checks specific metrics at defined intervals. This approach uses the while true construct combined with standard Linux commands.

Basic Syntax

while true; do
    date
    cat /proc/loadavg
    free
    sleep 600
done

Breaking Down the Command

• while true: Creates an infinite loop that continues until manually stopped
• date: Displays the current timestamp for each check
• cat /proc/loadavg: Shows the 1-minute, 5-minute, and 15-minute load averages
• free: Displays memory and swap usage statistics
• sleep 600: Pauses for 600 seconds (10 minutes) between checks

Example Output

Here’s what the monitoring output looks like:

[user@server ~]$ while true; do
    date
    cat /proc/loadavg
    free
    sleep 600
done

Mon Jan 25 18:52:26 CST 2026
16.80 9.99 4.23 17/760 473640
               total        used        free      shared  buff/cache   available
Mem:        49065224    32839616      763044    13857116    29796508    16225608
Swap:       24731644     1896372    22835272

Mon Jan 25 19:02:26 CST 2026
17.12 16.02 10.29 7/759 473766
               total        used        free      shared  buff/cache   available
Mem:        49065224    33099712      787048    13891812    29546760    15965512
Swap:       24731644     1809076    22922568

Mon Jan 25 19:12:26 CST 2026
17.28 17.16 13.63 4/760 473838
               total        used        free      shared  buff/cache   available
Mem:        49065224    33306620      845572    13908896    29298320    15758604
Swap:       24731644     1720500    23011144
...

Interpreting the Results

Load Average Values

The three numbers in /proc/loadavg represent:

• First number: 1-minute load average
• Second number: 5-minute load average
• Third number: 15-minute load average

A load average higher than your number of CPU cores typically indicates the system is under stress.

Memory Information

The free command shows:

• Total: Total installed memory
• Used: Memory currently in use
• Free: Completely unused memory
• Buff/cache: Memory used for buffers and cache
• Available: Memory available for new applications (more accurate than “free”)

Stopping the Monitor

To stop the monitoring loop, simply press Ctrl + C in the terminal. This sends an interrupt signal that terminates the loop.

Customization Options

Adjust the Monitoring Interval

Change the sleep value to modify how frequently checks occur:

sleep 300   # Check every 5 minutes
sleep 60    # Check every minute
sleep 3600  # Check every hour

Add Additional Metrics

You can expand the monitoring to include other system information:

while true; do
    date
    echo "=== Load Average ==="
    cat /proc/loadavg
    echo "=== Memory Usage ==="
    free -h
    echo "=== Disk Usage ==="
    df -h
    echo "=== Top Processes ==="
    ps aux --sort=-%cpu | head -6
    sleep 600
done

Save Output to a File

Redirect the output to a file for later analysis:

while true; do
    date
    cat /proc/loadavg
    free
    sleep 600
done >> system_monitor.log 2>&1

Using in Shell Scripts

This technique is particularly useful when incorporated into shell scripts for automated monitoring:

#!/bin/bash
# system_monitor.sh - Simple system monitoring script

LOG_FILE="/var/log/custom_monitor.log"
INTERVAL=600  # 10 minutes

while true; do
    {
        echo "===================="
        date
        echo "Load Average:"
        cat /proc/loadavg
        echo "Memory Status:"
        free -h
        echo ""
    } >> "$LOG_FILE"
    
    sleep "$INTERVAL"
done

Make the script executable and run it in the background:

chmod +x system_monitor.sh
nohup ./system_monitor.sh &

Best Practices

1. Choose appropriate intervals: Very frequent checks can consume resources; balance monitoring needs with system overhead
2. Log rotation: If saving to files, implement log rotation to prevent disk space issues
3. Use meaningful timestamps: Include date and time for easier troubleshooting
4. Monitor during specific events: Run the loop during database migrations, application deployments, or load testing
5. Combine with alerts: Parse the output to trigger notifications when thresholds are exceeded

Conclusion

This simple monitoring approach provides a lightweight alternative to full-featured monitoring tools when you need focused, periodic system checks. The flexibility of the while loop allows you to customize exactly what you monitor and how often, making it an invaluable tool in any system administrator’s toolkit.

Whether you’re troubleshooting performance issues, establishing baseline metrics, or monitoring system behavior during specific operations, this technique offers a quick and effective solution without the complexity of enterprise monitoring systems.