System resource monitoring (free, uptime, vmstat) in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the free command show in Linux?

The free command displays the amount of used and free memory in the system, including RAM and swap space. It helps you understand how much memory is available and how much is being used.

beginner

What information does the uptime command provide?

The uptime command shows how long the system has been running, the current time, how many users are logged in, and the system load averages for the last 1, 5, and 15 minutes.

intermediate

What is the purpose of the vmstat command?

The vmstat command reports information about processes, memory, paging, block IO, traps, and CPU activity. It helps monitor system performance and resource usage over time.

intermediate

How can you interpret the load average numbers shown by uptime?

Load averages represent the average number of processes waiting to run over 1, 5, and 15 minutes. A load average close to the number of CPU cores means the system is busy but not overloaded. Higher numbers indicate more demand than the CPU can handle.

intermediate

Which vmstat fields indicate CPU usage?

In vmstat, the CPU usage fields are us (user time), sy (system time), id (idle time), and wa (time waiting for IO). These help understand how the CPU is spending its time.

What does the free command NOT show?

A Memory usage details

B Swap space usage

C Available RAM

D CPU load averages

The free command shows memory and swap usage but does not show CPU load averages.

Which command shows how long the system has been running?

A vmstat

B uptime

C free

D top

The uptime command displays the system running time along with load averages.

In vmstat, what does the id field represent?

A Idle CPU time

B Input device usage

C Interrupts per second

D Disk IO

The id field in vmstat shows the percentage of CPU time spent idle.

What does a high load average compared to CPU cores indicate?

A System is overloaded

B System is under low load

C System is idle

D System has no users logged in

A load average higher than the number of CPU cores means more processes want CPU time than available, indicating overload.

Which command would you use to monitor memory and CPU usage over time?

A uptime

B free

C vmstat

D ls

vmstat provides ongoing reports of memory, CPU, and other system resource usage.

Explain how you would use free, uptime, and vmstat together to monitor a Linux system's health.

Think about what each command tells you and how they complement each other.

Describe what the load average numbers mean and how they relate to CPU cores.

Imagine how busy your kitchen is with cooks compared to the number of stoves.