Understanding your system's health and performance is essential for any DevOps engineer. You need to monitor several key metrics to ensure your Linux servers are running optimally. The main system metrics to watch include:

• CPU usage: shows how much processing power is being used;
• Memory usage: indicates how much RAM is currently in use and available;
• Disk usage: reveals how much storage space is consumed and how much is free;
• Network usage: tracks data sent and received on network interfaces.

Keeping an eye on these metrics helps you spot trends, anticipate problems, and react quickly to performance issues.

# Check memory usage
free -h

# View disk space usage
df -h

# Check disk usage for a specific directory
du -sh /var/log

# Monitor system performance statistics
vmstat 2 5

# Report CPU and disk statistics
iostat -xz 1 3

When you run these commands, you will see output that provides insight into your system's current state.

• For example, the free command displays total, used, and available memory, helping you understand if your system is running low on RAM;
• The df command shows disk space usage for mounted filesystems, which helps you avoid running out of storage;
• du lets you pinpoint which directories are consuming the most space;
• With vmstat, you get a snapshot of processes, memory, paging, block IO, and CPU activity, which can highlight resource contention;
• iostat helps you analyze CPU load and IO statistics, making it easier to identify bottlenecks in disk performance.

By interpreting these outputs, you can identify resource bottlenecks such as high memory consumption, full disks, or excessive CPU usage, and take action before they impact your applications.