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useradd.md

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useradd

The useradd command is used to create a new user account on a Linux system. It allows the system administrator to specify various attributes for the new user, such as home directory, shell, and group memberships.

Basic Usage

  • Syntax:

    useradd [options] username

  • Examples:

    sudo useradd newuser
    • Creates a new user account named newuser with default settings.
    sudo useradd -m -s /bin/bash newuser
    • Creates a new user account named newuser, with a home directory and Bash as the default shell.
    sudo useradd -G sudo newuser
    • Creates a new user account named newuser and adds them to the sudo group.

Common Options

  • -m or --create-home:

    • Creates the user's home directory if it does not exist.
    sudo useradd -m newuser
    • Creates a home directory /home/newuser for the user newuser.

  • -s [shell] or --shell [shell]:

    • Specifies the user's login shell.
    sudo useradd -s /bin/bash newuser
    • Sets /bin/bash as the default shell for newuser.

  • -G [group,...] or --groups [group,...]:

    • Adds the user to one or more supplementary groups.
    sudo useradd -G sudo,users newuser
    • Adds newuser to the sudo and users groups.

  • -d [dir] or --home [dir]:

    • Specifies the home directory for the user.
    sudo useradd -d /custom/home newuser
    • Sets /custom/home as the home directory for newuser.

  • -c [comment] or --comment [comment]:

    • Adds a comment (often the full name of the user) to the account.
    sudo useradd -c "John Doe" newuser
    • Sets "John Doe" as the GECOS (comment) field for newuser.

  • -e [date] or --expiredate [date]:

    • Sets the account expiration date.
    sudo useradd -e 2024-12-31 newuser
    • Expires the account newuser on December 31, 2024.

  • -f [days] or --inactive [days]:

    • Specifies the number of days after a password expires until the account is disabled.
    sudo useradd -f 30 newuser
    • Disables newuser's account 30 days after the password expires.

  • --help:

    • Displays help information about the useradd command.
    useradd --help
    • Shows usage information and available options.

Quick Tips

  • Creating a User with Default Settings:

    • Simply use useradd followed by the username.
    sudo useradd username
    • Creates the user with default settings, but without a home directory or password.

  • Creating a User with a Home Directory and Shell:

    • Use the -m and -s options to create a more fully configured user.
    sudo useradd -m -s /bin/zsh username
    • Creates a user with a home directory and sets the Zsh shell as default.

  • Adding a User to Groups:

    • Use the -G option to add the user to multiple groups during account creation.
    sudo useradd -G wheel,docker username
    • Adds the user to the wheel and docker groups.

  • Setting an Expiration Date:

    • Use -e to specify when the user account should expire.
    sudo useradd -e 2025-01-01 username
    • Expires the account on January 1, 2025.

Summary

The useradd command is a powerful tool for creating new user accounts on a Linux system. It allows for significant customization during account creation, including setting home directories, shells, group memberships, and more. Understanding the key options of useradd can help efficiently manage users in a Linux environment.