How to Add or Modify User in Linux – Managing user accounts with useradd and usermod

guidesecurity

The useradd and usermod commands are fundamental tools in Linux for managing user accounts. They enable administrators to add new users and modify existing user parameters.

Understanding useradd and usermod

useradd is a command-line utility employed to create new user accounts within a Linux environment. Administrators utilize this to incorporate new users into the system. It generates a new entry in the user database, establishes the user’s home directory, and assigns both a unique User ID (UID) and Group ID (GID).

usermod allows modification of current user accounts. It facilitates alterations to a user’s attributes, including their home directory, shell, password, and group affiliations.

Common Uses

These commands are vital for system administrators managing Linux systems. Applications range from initial user setup to account maintenance and permission adjustments.

Programming Language

useradd and usermod are implemented using the C programming language.

Installation Procedures

Typically, useradd and usermod come pre-installed, being core components of Linux. If missing, install them via your distribution’s package manager.

Ubuntu/Debian Installation

Use the following command:

sudo apt-get install passwd

CentOS/RHEL Installation

Use the command:

sudo yum install passwd

Practical Examples

Creating a User Account

The general syntax for creating a new user is:

sudo useradd username

This creates a user with the specified username. The home directory resides in /home, and a unique UID/GID is assigned.

Modifying an Existing Account

Modify users with:

sudo usermod options username

This allows adjustments to different parameters, like the user’s home directory, login shell, and group memberships.

Alternative Commands and Packages

Alternatives to useradd and usermod include:

adduser: A more user-friendly command for adding user accounts.
userdel: Removes user accounts.
chsh: Modifies the user’s login shell.
passwd: Changes user passwords.

Example Scripts

Script 1: User Creation

Demonstrates creating a new user.

#!/bin/bash

# Prompt for username
read -p "Enter the username: " username

# Create the user
sudo useradd $username

# Set initial password
sudo passwd $username

Script 2: User Modification

Illustrates modifying a user’s home directory.

#!/bin/bash

# Prompt for username
read -p "Enter the username: " username

# Prompt for new home directory
read -p "Enter the new home directory: " home_directory

# Modify the user account
sudo usermod -d $home_directory $username

Script 3: User Deletion

Demonstrates deleting a user account.

#!/bin/bash

# Prompt for the username
read -p "Enter the username: " username

# Delete the user account
sudo userdel $username

Function/Command Summary

Command	Description
useradd	Create User
usermod	Modify User
userdel	Delete User
chsh	Change Login Shell
passwd	Change Password

Conclusion

useradd and usermod are vital for managing Linux user accounts. They offer administrators control over account creation, modification, and customization. Their proper use maintains security and functionality within Linux environments.

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