Linux User Creation Bash Script

Victor Gentle — Mon, 01 Jul 2024 12:44:33 +0000

As part of the HNG Internship program, we were tasked with creating a bash script named create_users.sh to automate the creation of new users and groups on a Linux system.
Learn more about HNG

Overview

This script, create_users.sh, automates the creation of users and their associated groups, sets up their home directories, generates random passwords, and logs all actions. The script reads from a specified text file containing usernames and group names.

Prerequisites

The script must be run with root privileges.
Ensure the input file with usernames and groups is formatted correctly and exists.

Input File Format

Each line in the input file should be formatted as follows:

username;group1,group2,...

Example:

light;sudo,dev,www-data
idimma;sudo
mayowa;dev,www-data

Script Steps

Check Root Privileges:

if [[ $EUID -ne 0 ]]
The script starts by checking if it is being run as the root user.
This is necessary because creating users and modifying system files requires root privileges.
This ensures that the script has the necessary permissions to perform its tasks.

Validate Input File:

if [[ -z "$1" ]]; then echo "Usage: $0 " >&2
The script checks if the input file is provided as an argument and whether it exists.

Setup Logging and Password Files:

The script sets up the log file and the password file. It ensures the directories exist and sets appropriate permissions for the password file

mkdir -p: Ensures the directories exist.
> "$LOG_FILE" and > "$PASSWORD_FILE": Create or clear the log and password files.
chmod 600 "$PASSWORD_FILE": Ensures that only the owner can read the password file, enhancing security.

Generate Passwords:

generate_password() { < /dev/urandom tr -dc A-Za-z0-9 | head -c12
The script defines a function to generate random passwords for the new users.

Log Messages:

log_message() { local message="$1" echo "$(date '+%Y-%m-%d %H:%M:%S') : $message" >> "$LOG_FILE"
The script defines a function to log messages with timestamps.
This provides a way to track actions performed by the script, useful for auditing and debugging.

Process Each Line:

The script reads and processes each line from the input file, creating users and groups, setting up home directories, generating passwords, and logging actions.

IFS=';' read -r username groups: Reads the username and groups from each line.
username=$(echo "$username" | xargs) and groups=$(echo "$groups" | xargs): Removes leading/trailing whitespace.
getent group "$username": Checks if the user's personal group exists; creates it if it doesn't.
id "$username": Checks if the user already exists.
password=$(generate_password): Generates a random password for the user.
useradd -m -g "$username" -s /bin/bash "$username": Creates the user with the specified home directory and personal group.
echo "$username:$password" | chpasswd: Sets the user's password.
IFS=',' read -r -a group_array <<< "$groups": Splits the groups into an array.
groupadd "$group": Creates additional groups if they don't exist.
usermod -aG "$group" "$username": Adds the user to the additional groups.

Final Message:

log_message "User creation script completed successfully" echo "User creation script completed. Check the log file at $LOG_FILE and passwords at $PASSWORD_FILE."
The script logs a completion message and prints a final status to the console.
Notifies the user of the script's completion and provides locations for the log and password files.

Usage

Save the script as create_users.sh and make it executable:

chmod +x create_users.sh

Run the script with the user file as an argument:

sudo ./create_users.sh <name-of-text-file>

Logs and Password Storage

Log File: /var/log/user_management.log contains logs of all actions performed.
Password File: /var/secure/user_passwords.csv stores the generated passwords securely.

Example User File

Create a file named user_list.txt with the following content:

light;sudo,dev,www-data
idimma;sudo
mayowa;dev,www-data

Run the script

sudo ./create_users.sh user_list.txt

This script ensures that users and groups are created as specified, with appropriate permissions and logging.

Learn More About HNG Internship

The HNG Internship is a remote internship program designed to find and develop the most talented software developers. It offers a stimulating environment for interns to improve their skills and showcase their abilities through real-world tasks.

DEV Community: Victor Gentle