su (switch user) in Linux CLI - Step-by-Step Execution

Concept Flow - su (switch user)

User runs 'su'

↓

Prompt for password

↓

User enters password

↓

Password correct?

No→Access denied, exit

Yes↓

Switch to target user shell

↓

User works as new user

↓

Exit shell to return to original user

The 'su' command asks for the target user's password, then switches the shell to that user if the password is correct.

Execution Sample

Linux CLI

su - alice
# Enter password when prompted
whoami

Switch to user 'alice' and then check which user is active.

Execution Table

Step	Action	Input/Condition	Result	Output
1	Run 'su - alice'	Command entered	Prompt for alice's password
2	Enter password	Password correct?	Yes
3	Switch user	Shell changes to alice	User is now alice
4	Run 'whoami'	Check current user	Output username	alice
5	Exit shell	User types 'exit'	Return to original user shell

💡 User exits alice's shell to return to original user

Variable Tracker

Variable	Start	After su command	After password	After switch	After exit
current_user	original_user	original_user	original_user	alice	original_user

Key Moments - 3 Insights

Why does 'su' ask for a password even if I am already logged in?

Because 'su' switches to another user, it requires that user's password for security, as shown in step 2 of the execution_table.

What happens if I enter the wrong password?

The command denies access and does not switch users, stopping at step 2 with 'Password correct?' = No.

How do I return to my original user after switching?

You type 'exit' to leave the switched user's shell, returning to your original user as in step 5.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output of 'whoami' after switching user?

A original_user

B alice

C root

D su

💡 Hint

Check step 4 in the execution_table where 'whoami' is run after switching user.

At which step does the shell actually change to the new user?

A Step 1

B Step 2

C Step 3

D Step 5

💡 Hint

Look at the 'Result' column in the execution_table for when the user changes.

If the password entered is incorrect, what happens?

A Access denied and exit su

B Switch user anyway

C Prompt for password again indefinitely

D Switch to root user

💡 Hint

Refer to key_moments and the flow where password correctness is checked.

Concept Snapshot

su (switch user) command:
- Syntax: su [options] [username]
- Prompts for target user's password
- On success, opens a shell as that user
- Use 'exit' to return to original user
- Commonly used to switch to root or other users

Full Transcript

The 'su' command lets you switch from your current user to another user on the system. When you run 'su' with a username, it asks for that user's password. If you enter the correct password, your shell changes to that user, letting you work with their permissions. You can check who you are by running 'whoami'. When done, type 'exit' to go back to your original user. If the password is wrong, access is denied and you stay as your original user.