How to use the command 'nologin' (with examples)

The ’nologin’ command is an alternative shell that prevents a user from logging in. It is often used when you want to deny access to a user, while still allowing other system services to function normally. The command sets the user’s login shell to ’nologin’, which means they will not be able to log in or access the system interactively.

Use case 1: Set a user’s login shell to ’nologin’ to prevent the user from logging in

Code:

chsh -s user nologin

Motivation: The motivation behind setting a user’s login shell to ’nologin’ is to restrict their access to the system. This can be useful when you want to disable an account temporarily or deny login access to a specific user.

Explanation:

• chsh: The chsh command is used to change a user’s login shell.
• -s user: The -s option specifies the user whose login shell will be modified.
• nologin: The ’nologin’ shell is used to prevent a user from logging in.

Example output:

$ chsh -s user nologin
Password:
Changing shell for user.
Shell changed.

Use case 2: Customize message for users with the login shell of ’nologin'

Code:

echo "declined_login_message" > /etc/nologin.txt

Motivation: The motivation behind customizing the message for users with the login shell of ’nologin’ is to provide them with a specific reason or explanation for why their login attempt was declined. This can help them understand the situation and take appropriate action.

Explanation:

• echo: The echo command is used to print a message or text.
• "declined_login_message": This is the message that will be displayed to users with the login shell of ’nologin'.
• /etc/nologin.txt: This is the file where the message will be stored.

Example output:

$ echo "Your login has been declined due to maintenance. Please try again later." > /etc/nologin.txt

Conclusion: The ’nologin’ command provides a simple and effective way to prevent a user from logging in. It can be used to restrict access to a system or provide a specific message to users whose login attempts are declined. By using the ’nologin’ command, you can maintain control over user access and communicate important information to them.