12 Essential Linux Commands to Monitor Memory Usage

When optimizing a Linux system, monitoring physical memory is crucial, and Linux offers many utilities to observe memory usage. The following list describes twelve methods, ranging from simple file reads to graphical monitors, each with example commands.

/proc/meminfo

The virtual file /proc/meminfo provides a dynamic snapshot of memory statistics, serving as the data source for tools like free, ps, and top. Process‑specific memory can also be examined via /proc/<pid>/statm and /proc/<pid>/status.

cat /proc/meminfo

atop

The atop command runs in a terminal and displays a colored, comprehensive view of CPU, memory, network, I/O, and kernel activity, especially useful under high load.

sudo atop

free

free

offers a quick overview of memory usage by summarizing the information gathered from /proc/meminfo.

free -h

GNOME System Monitor

A graphical tool that shows recent CPU, memory, swap, and network usage, allowing users to inspect processes and resource consumption.

gnome-system-monitor

htop

htop

provides a real‑time, interactive view of each process's memory usage, including resident set size, shared libraries, and total memory per process, with scrollable lists.

htop

KDE System Monitor

Provides functionality similar to the GNOME monitor, invoked with ksysguard.

ksysguard

memstat

memstat

identifies virtual memory usage of executables, processes, and shared libraries. With a PID, it lists associated files, data, and libraries.

memstat -p

nmon

An ncurses‑based benchmark tool that monitors CPU, memory, I/O, filesystem, and network. For memory, it shows total and free memory and swap usage in real time.

nmon

ps

The ps command can display each process's memory usage, including %MEM, VSZ, and RSS. Sorting by RSS is possible with the --sort -rss option.

ps aux --sort -rss

smem

smem

aggregates memory usage per process and per user based on /proc data, and can export charts such as bar or pie graphs.

sudo smem --pie name -c "pss"

top

top

provides a live view of running programs and their resource consumption, allowing sorting by memory usage.

top

vmstat

vmstat

reports both real‑time and averaged statistics for CPU, memory, and I/O. It shows physical and virtual memory usage.

vmstat

This collection equips Linux administrators with a comprehensive toolbox for tracking memory consumption, from low‑level file reads to full‑featured graphical monitors.