Understanding the useradd Command

Basic Usage of useradd

The useradd command is used to create a new user account on a Linux system. It is typically run with superuser privileges and allows administrators to specify various options to configure the new user's account settings.

Common Options for useradd

The useradd command supports a variety of options:

• -d, --home - Specify the home directory for the new user. Default is /home/USERNAME.
• -m, --create-home - Create the user's home directory if it does not exist.
• -s, --shell - Specify the user's login shell. Default is usually /bin/bash.
• -G, --groups - Specify a comma-separated list of supplementary groups for the user.
• -u, --uid - Specify a numerical user ID for the new user.
• -g, --gid - Specify the primary group for the new user.
• -p, --password - Set the user's password (encrypted).
• -e, --expiredate - Set an expiration date for the user's account.
• -f, --inactive - Set the number of days after a password expires until the account is disabled.
• -r, --system - Create a system account.
• -h, --help - Display help information and exit.

Examples of useradd Command

Create a New User

This command creates a new user named newuser with default settings.

Create a User with a Home Directory

This command creates a new user newuser and also creates a home directory at /home/newuser.

Create a User with a Specific Shell

This command creates a new user newuser with the Zsh shell as the login shell.

Create a User and Assign to a Group

This command creates newuser and assigns them to the developers primary group.

Create a User with an Expiration Date

This command creates newuser and sets their account to expire on December 31, 2025.

Understanding User Creation Process

When a user is created using the useradd command:

• The user's information is added to the /etc/passwd file.
• A home directory may be created based on the options provided.
• Default configuration files may be copied to the new user's home directory.

Summary of Options