System resource monitoring (free, uptime, vmstat) in Linux CLI - Step-by-Step Execution

Concept Flow - System resource monitoring (free, uptime, vmstat)

Run 'free' command

↓

Display memory usage

↓

Run 'uptime' command

↓

Show system uptime and load

↓

Run 'vmstat' command

↓

Show CPU, memory, IO stats

↓

End of monitoring snapshot

The flow shows running three commands one after another to get memory, uptime, and system stats snapshots.

Execution Sample

Linux CLI

free
uptime
vmstat 1 2

Runs free to show memory, uptime for system time/load, vmstat for CPU/memory stats twice with 1 second interval.

Execution Table

Step	Command	Output Summary	Details
1	free	Shows total, used, free memory and swap	Mem: total=8000MB, used=3000MB, free=5000MB; Swap: total=2000MB, used=0MB, free=2000MB
2	uptime	Shows system uptime and load averages	Uptime=5 days 3:20, Load averages=0.15, 0.10, 0.05
3	vmstat 1 2 (first)	First vmstat snapshot	r=1, b=0, swpd=0, free=5000, buff=200, cache=1000, si=0, so=0, bi=10, bo=5, in=100, cs=200, us=5, sy=3, id=90, wa=2, st=0
4	vmstat 1 2 (second)	Second vmstat snapshot after 1 second	r=0, b=0, swpd=0, free=4800, buff=250, cache=1100, si=0, so=0, bi=5, bo=3, in=90, cs=180, us=3, sy=2, id=95, wa=0, st=0
5	End	Monitoring snapshot complete	All commands executed, system stats captured

💡 All commands completed, system resource snapshot taken

Variable Tracker

Variable	Start	After free	After uptime	After vmstat 1	After vmstat 2	Final
Memory Used (MB)	unknown	3000	3000	3000	3000	3000
Memory Free (MB)	unknown	5000	5000	5000	4800	4800
System Uptime	unknown	unknown	5 days 3:20	5 days 3:20	5 days 3:20	5 days 3:20
CPU Usage User (%)	unknown	unknown	unknown	5	3	3
CPU Idle (%)	unknown	unknown	unknown	90	95	95

Key Moments - 3 Insights

Why does vmstat show two sets of data when we run 'vmstat 1 2'?

The first vmstat output shows stats since last reboot, the second is the real snapshot after 1 second interval (see rows 3 and 4 in execution_table).

What does the 'load average' in uptime mean?

Load average shows average system demand over 1, 5, and 15 minutes, indicating how busy the CPU is (see row 2 in execution_table).

Why is free memory different between free and vmstat outputs?

free shows memory including buffers/cache, vmstat separates free memory and buffers/cache (see variable_tracker Memory Free values).

Visual Quiz - 3 Questions

Look at the execution_table row 2, what is the system uptime shown by 'uptime'?

A 5 hours 3 minutes

B 5 days 3:20

C 3 days 5:20

D Unknown

💡 Hint

Check the 'Output Summary' and 'Details' columns in execution_table row 2.

At which vmstat snapshot does CPU idle percentage increase?

A Second snapshot

B First snapshot

C Both snapshots are equal

D CPU idle is not shown

💡 Hint

Compare 'CPU Idle (%)' in variable_tracker after vmstat 1 and vmstat 2.

If the system had more swap used, which command output would show it clearly?

A vmstat

B uptime

C free

D None of these

💡 Hint

Look at the 'free' command output in execution_table row 1 showing swap usage.

Concept Snapshot

System resource monitoring uses commands:
- free: shows memory and swap usage
- uptime: shows system running time and load averages
- vmstat: shows CPU, memory, IO stats in intervals
Run them sequentially for a snapshot of system health.

Full Transcript

This visual execution shows how to monitor system resources on Linux using three commands: free, uptime, and vmstat. First, 'free' displays memory and swap usage, telling how much RAM is used and free. Next, 'uptime' shows how long the system has been running and the load averages, which indicate CPU demand. Finally, 'vmstat' gives detailed CPU, memory, and IO statistics, showing two snapshots with a 1-second gap. The execution table traces each command's output step-by-step, and the variable tracker follows key values like memory used, free memory, uptime, and CPU usage. Key moments clarify common confusions like why vmstat shows two outputs and what load averages mean. The quiz tests understanding by asking about uptime, CPU idle changes, and swap usage visibility. This helps beginners see how these commands work together to give a clear picture of system health.