Master Linux System Monitoring: Essential Commands & Smem Tips

Command Line Learning Shortcut

Linux commands are powerful for everything from simple file operations to complex multimedia processing, but beginners often know commands without understanding how to troubleshoot system failures. The key is to combine theoretical knowledge with practical system operations.

5 Major System Operation States

For operations, checking system status is fundamental. To monitor CPU, memory, processes, disks, and network you need commands such as ls, ps, free, top, uptime, ifconfig, su / sudo, dmesg, iostat, vmstat, sar, htop, iotop, smem. This article highlights a few especially efficient commands.

Typical Linux Commands

Because Linux uses virtual memory, calculating a process's actual physical memory usage is non‑trivial. smem is a command‑line tool that provides detailed memory‑usage reports.

Memory Status Detection Tool

To install smem, enable the EPEL repository and install the required packages:

yum install epel-release
yum install smem python-matplotlib python-tk

Run smem with options to display per‑process memory usage:

The -k flag shows memory units, -s sorts, and uss sorts by unshared set size, producing a clear list of memory consumption. smem can also show memory usage as a percentage with the -p option, and per‑user usage with -u. Example commands:

smem -P nginx
smem -k -P nginx

Thus smem makes it easy to obtain each process's memory footprint, an essential tool for operations.

CPU/Memory Intensive Processes

To list the top 10 CPU‑consuming processes, combine ps and sort:

ps aux | head -1
ps aux | sort -rn -k3 | head -10

The first line prints the header. The pipeline sorts all processes by the third column (%CPU) in descending order and shows the top ten.

Removing Zombie Processes

A zombie process remains after its child exits but before the parent reaps it. Detect zombies with: ps -e -o stat,ppid,pid,cmd | egrep '^[Zz]' To kill all zombies in bulk:

ps -e -o stat,ppid,pid,cmd | grep -e '^[Zz]' | awk '{print $2}' | xargs kill -9

This pipeline uses grep to filter zombie entries, awk to extract the parent PID, and xargs to pass those PIDs to kill -9.