User Management

In this guide, you'll learn essential commands for creating and managing user accounts on Linux. This tutorial covers adding users, customizing account settings, and managing groups, ensuring you understand both the basics and some advanced options.

Creating a New User

The primary command to add a new local user is useradd. System administrators typically use this command to add new users. For example, to create a new user named Bob, execute:

[~]$ useradd bob

This command creates Bob with a system-generated UID and GID. By default, Bob's home directory is set to /home/bob (based on the system's default configuration) and his login shell is set to /bin/sh.

To set a password for Bob's account, use the passwd command:

[~]$ passwd bob

After logging in, a user can confirm their current username by running the whoami command. Additionally, users can change their password at any time by simply running passwd without any additional arguments.

Using Options with useradd

The useradd command supports several options that allow you to customize the user creation process. Here are some commonly used options:

• -u: Specify a custom UID.
• -g: Specify the primary group via a custom GID.
• -d: Define a custom home directory path.
• -s: Set the default login shell.
• -c: Add a comment (often used for a user description).
• -e: Set the account expiration date.
• -G: Add the new user to additional (secondary) groups.

For example, to create Bob with a custom UID, GID, home directory, shell, and an account comment, use:

[~]$ useradd -u 1009 -g 1009 -d /home/robert -s /bin/bash -c "Mercury Project member" bob

This command assigns Bob a UID and a primary GID of 1009, sets his home directory to /home/robert, selects /bin/bash as his login shell, and includes the comment "Mercury Project member" in his account information.

You can validate Bob's settings with the id command:

[~]$ id bob
uid=1009(bob) gid=1009(avenger) groups=1009(avenger)

Additionally, inspect the /etc/passwd file to verify the custom comment and other account details:

[~]$ grep -i bob /etc/passwd
bob:x:1009:1009:Mercury Project member:/home/robert:/bin/bash

User Deletion and Group Management

To delete a user account, use the userdel command followed by the username:

[~]$ userdel bob

Managing groups is equally essential. Below are commands for adding and deleting groups:

• Adding a New Group: Use the groupadd command. The -g option lets you specify a custom GID.

  [~]$ groupadd -g 1010 newgroup
  

• Deleting a Group: Use the groupdel command along with the group name.

  [~]$ groupdel newgroup
  

Hands-On Practice

Happy learning!

Additional Resources

• Linux Documentation
• User Management Best Practices