top and htop (live monitoring) in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the top command in Linux?

The top command shows a live, updating list of running processes and system resource usage like CPU and memory.

beginner

How does htop improve on top?

htop provides a colorful, interactive interface with easier navigation and process management using keyboard shortcuts.

intermediate

Which key do you press in htop to kill a selected process?

Press F9 to kill the selected process in htop.

intermediate

How can you sort processes by memory usage in top?

Press M (uppercase) while top is running to sort processes by memory usage.

beginner

What command do you use to install htop on Ubuntu?

Use sudo apt install htop to install htop on Ubuntu.

Which command shows a live list of running processes in Linux?

A cd

B ls

C top

D mkdir

top displays a live updating list of running processes and system resource usage.

What feature does htop provide that top does not?

A Listing files

B Interactive process management

C Changing directories

D Creating files

htop allows interactive process management with keyboard shortcuts.

In top, which key sorts processes by CPU usage?

A P

B M

C K

D Q

Pressing P sorts processes by CPU usage in top.

How do you exit the top command?

A F10

B Ctrl+C

C Esc

D Q

Press Q to quit the top command.

Which command installs htop on Debian-based systems?

A sudo apt install htop

B sudo yum install htop

C sudo pacman -S htop

D sudo dnf install htop

Use sudo apt install htop on Debian/Ubuntu systems.

Explain how to use top to monitor system processes and sort them by memory usage.

Think about the keys you press while top is running.

Describe the advantages of using htop over top for live monitoring.

Focus on usability and features.

Practice

1. What is the main purpose of the top command in Linux?

easy

A. To display live system and process information

B. To edit text files

C. To compile programs

D. To manage user accounts

Solution

1. Step 1: Understand the function of top

   The top command shows real-time information about system processes and resource usage.

2. Step 2: Compare with other options

   Options B, C, and D relate to different commands or tools, not top.

3. Final Answer:

   To display live system and process information -> Option A

4. Quick Check:

   top = live system info [OK]

Hint: Remember: top shows live system stats [OK]

Common Mistakes:

• Confusing top with text editors like nano
• Thinking top manages users
• Assuming top compiles code

2. Which of the following commands correctly starts htop in the terminal?

easy

A. start htop

B. htop -start

C. htop &

D. run htop

Solution

1. Step 1: Identify correct syntax to run htop

   The command htop runs the program; adding & runs it in background.

2. Step 2: Check other options for correctness

   Options B, C, and D are not valid Linux commands to start htop.

3. Final Answer:

   htop & -> Option C

4. Quick Check:

   Run htop with 'htop &' [OK]

Hint: Run htop by typing 'htop' or 'htop &' [OK]

Common Mistakes:

• Using invalid flags like -start
• Typing 'start htop' which is Windows style
• Using 'run htop' which is not a Linux command

3. You run top and see a process using 95% CPU. What does this indicate?

medium

A. The process is waiting for user input

B. The process is sleeping and not active

C. The process is stopped

D. The process is using most of the CPU power

Solution

1. Step 1: Interpret CPU usage in top

   High CPU percentage means the process is actively using CPU resources.

2. Step 2: Understand other states

   Sleeping or waiting processes use little CPU; stopped processes do not use CPU.

3. Final Answer:

   The process is using most of the CPU power -> Option D

4. Quick Check:

   High CPU% = active process [OK]

Hint: High CPU% means active process using CPU [OK]

Common Mistakes:

• Thinking high CPU means sleeping
• Confusing waiting with stopped
• Assuming stopped processes use CPU

4. You try to run htop but get: command not found. What should you do?

medium

A. Restart the computer

B. Install htop using the package manager

C. Run top instead

D. Check if you typed htop correctly

Solution

1. Step 1: Understand 'command not found' error

   This means htop is not installed or not in PATH.

2. Step 2: Fix by installing htop

   Use package manager like sudo apt install htop or sudo yum install htop to install.

3. Final Answer:

   Install htop using the package manager -> Option B

4. Quick Check:

   command not found = install missing tool [OK]

Hint: Install missing commands with package manager [OK]

Common Mistakes:

• Restarting without installing
• Ignoring the error and running top
• Not checking spelling before install

5. You want to find and kill the process using the most memory using htop. What steps should you follow?

hard

A. Sort by memory, select process, press F9 to kill

B. Sort by CPU, select process, press F10 to kill

C. Sort by PID, select process, press F3 to kill

D. Sort by user, select process, press F5 to kill

Solution

1. Step 1: Sort processes by memory usage in htop

   Press F6 or click the memory column to sort descending by memory.

2. Step 2: Select the top memory-consuming process and kill it

   Use arrow keys to select process, then press F9 to kill it.

3. Final Answer:

   Sort by memory, select process, press F9 to kill -> Option A

4. Quick Check:

   htop kill = sort mem + F9 [OK]

Hint: In htop, F9 kills selected process after sorting [OK]

Common Mistakes:

• Using wrong function keys to kill
• Sorting by CPU instead of memory
• Trying to kill by PID without selecting