Monitoring RAM (Random Access Memory) usage is a key part of maintaining a stable and high-performing Linux system. Whether you’re running a local workstation or managing a production server, high memory usage can lead to performance drops, application crashes, or system instability.

In this article, we’ll cover the most useful commands and tools to check memory consumption in Linux — from simple terminal outputs to advanced real-time monitoring utilities.

1. free — Quick Overview of Memory Usage

free -h

This command displays the total amount of used, free, and available memory.

Useful flags:

  • -h: Human-readable format (MB/GB)
  • used: Total used memory
  • available: How much memory is still available for new applications

2. top — Real-Time System Monitoring

top

This interactive utility shows a live view of system resources, including:

  • Total and used memory
  • CPU usage
  • Active processes
  • Memory consumption per process

Press M inside top to sort by memory usage.

3. htop — Enhanced Version of top

htop

htop offers a user-friendly, colorful interface with mouse support and better filtering. You may need to install it first:

sudo apt install htop     # Debian/Ubuntu
sudo yum install htop     # CentOS/RHEL

It’s perfect for real-time process monitoring and quickly killing memory-heavy tasks.

4. vmstat — Virtual Memory Statistics

vmstat -s

This provides a snapshot of system memory, swap usage, and CPU activity.

Great for quick system health checks and diagnosing memory pressure or excessive swapping.

5. ps — Process-Specific RAM Usage

ps aux --sort=-%mem | head

This lists the top memory-consuming processes.

Key fields:

%MEM: Percentage of RAM used

RSS: Resident Set Size — actual physical memory used by a process

6. smem — Advanced Memory Reporting

sudo apt install smem
smem

Unlike ps or top, smem calculates PSS (Proportional Set Size), which gives a more accurate view of shared memory between processes — especially useful for identifying real memory consumption.

7. glances — All-in-One System Monitor

sudo apt install glances
glances

glances displays real-time usage stats for RAM, CPU, disk, network, processes, and more in one comprehensive view. Excellent for holistic system monitoring.

 Bonus: Check RAM via /proc

cat /proc/meminfo

This file contains detailed memory information directly from the kernel — useful for scripting and deeper debugging.

 Conclusion

Linux provides many built-in tools to monitor memory usage — from lightweight commands like free and ps, to powerful real-time dashboards like htop, glances, and smem.

For everyday use, htop and free -h offer a clear overview. For more in-depth analysis or troubleshooting, try vmstat, smem, or glances.

Effective memory monitoring is essential for system performance and reliability — especially on production servers.