Managing Users and Using `sudo`

Learn how to manage users, use the `sudo` command, and change passwords in a Unix-like system with simple and easy-to-understand instructions.

Introduction

When using a Unix-like system, like Linux on your Raspberry Pi, it’s important to know how to manage users and their permissions. This lesson will teach you how to add and manage users, how to use the sudo command to run important tasks, and how to change passwords.

Learning Objectives

• Understand what the sudo command does and how to use it.
• Learn how to add, delete, and manage users.
• Change user passwords using the passwd command.

Understanding sudo

The sudo command (which stands for “superuser do”) lets you run commands with special permissions. This is useful when you need to do things that require more control over the system, like installing software or changing system settings.

How to Use sudo:

To use sudo, you put it in front of the command you want to run with higher permissions. For example:

sudo apt update

This command updates the list of software packages on your system, but since it needs special permissions, you use sudo first. Usually, you’ll be asked to type in your password to confirm that you have permission to use sudo.

Why Use sudo Instead of Logging in as Root?

• Safety: Using sudo helps prevent mistakes because you only use special permissions when needed.
• Security: It keeps track of who uses sudo, so you know who did what on the system.
• Control: You can decide which users are allowed to use sudo by setting up permissions.

Adding and Managing Users

1. Adding a New User:

To add a new user to your system, you use the adduser command:

sudo adduser username

Replace username with the name you want to give the new user. The system will ask you to set a password for the new user and give some extra information (like the full name), but you can skip these extra details if you want.

2. Deleting a User:

To remove a user from the system, use the deluser command:

sudo deluser username

If you also want to delete the user’s home directory (where their files are stored), use this command:

sudo deluser --remove-home username

3. Giving a User sudo Permissions:

If you want a user to be able to use sudo, you need to add them to the sudo group:

sudo usermod -aG sudo username

This command adds the user to the group that’s allowed to use sudo. The -aG part means “append to group,” so the user stays in their other groups too.

Changing Passwords

1. Changing Your Own Password:

To change your own password, use the passwd command:

passwd

The system will ask you to enter your current password and then type your new password twice to confirm it.

2. Changing Another User’s Password:

If you have sudo permissions, you can change another user’s password by typing:

sudo passwd username

After entering your own password (to use sudo), the system will let you set a new password for the user.

3. Making a User Change Their Password on Next Login:

If you want to force a user to change their password the next time they log in, use this command:

sudo passwd -e username

This expires the current password, so the user has to set a new one the next time they log in.

Managing Groups

Groups are a way to organize users, so you can give several users the same permissions at once. Here’s how you can manage groups:

• Create a New Group:

  sudo groupadd groupname
  

• Add a User to a Group:

  sudo usermod -aG groupname username
  

• Remove a User from a Group:

  sudo deluser username groupname
  

Summary

In this lesson, you learned how to use the sudo command to do tasks that need special permissions, how to manage users on your system, and how to change passwords. These are important skills for keeping your system safe and making sure everyone has the right access.

Practice Exercise

Try these tasks to practice what you’ve learned:

1. Add a new user: Create a user called student and give them sudo permissions.
2. Change your password: Update your current password using the passwd command.
3. Manage groups: Create a new group called developers and add the student user to this group.

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