Introduction

This technical article is about the creation of a bash script named create_users.sh designed to automate user and group management on a Linux system. This script is part of the DevOps Stage 1 task for the HNG Internship. It reads a text file (user_lists.txt) with employee usernames and their respective groups, creates the users and groups, sets up home directories with appropriate permissions and ownership, generates random passwords for the users, and logs all actions. The script also securely stores the generated passwords.

Prerequisites

Basic knowledge of bash scripting.
Root access to a Linux system.
Git installed on your system.
A remote Git repository (e.g., GitHub).

Step 1: Creating the Input File

First, you need an input file that lists the users and their associated groups. Create a file named users.txt with this format:

ronke; sudo,dev,admin
charity; sudo
mosh; designer,admin

Step 2: Writing the Bash Script

Next, you write a bash script named create_users.sh to automate the user and group management tasks.

#!/bin/bash

set -x  # Enable debugging output

# Check if the script is run as root
if [ "$EUID" -ne 0 ]; then
  echo "Please run as root"
  exit 1
fi

# Check if input file is provided
if [ -z "$1" ]; then
  echo "Usage: $0 <input_file>"
  exit 1
fi

# Define the input file and log files
INPUT_FILE="$1"
LOG_FILE="/var/log/user_management.log"
PASSWORD_FILE="/var/secure/user_passwords.txt"

# Ensure /var/secure directory exists
mkdir -p /var/secure
chmod 700 /var/secure

# Clear previous log entries
> "$LOG_FILE"

# Function to generate a random password
generate_password() {
  local password_length=12
  tr -dc A-Za-z0-9 </dev/urandom | head -c $password_length
}

# Read the input file line by line
while IFS=';' read -r username groups; do
  # Remove leading and trailing whitespaces
  username=$(echo "$username" | xargs)
  groups=$(echo "$groups" | xargs)

  # Create user and personal group
  if id "$username" &>/dev/null; then
    echo "User $username already exists. Skipping creation..." | tee -a "$LOG_FILE"
  else
    # Create the user with a home directory
    useradd -m "$username" -s /bin/bash
    if [ $? -eq 0 ]; then
      echo "Created user $username" | tee -a "$LOG_FILE"

      # Create personal group with the same name as the username
      usermod -aG "$username" "$username"

      # Set the home directory permissions
      chmod 700 /home/"$username"
      chown "$username":"$username" /home/"$username"

      # Generate a random password
      password=$(generate_password)
      echo "$username:$password" | chpasswd

      # Store the password securely
      echo "$username:$password" >> "$PASSWORD_FILE"
      chmod 600 "$PASSWORD_FILE"

      echo "Password for $username stored securely" | tee -a "$LOG_FILE"
    else
      echo "Failed to create user $username" | tee -a "$LOG_FILE"
      continue
    fi
  fi

  # Create and add groups to the user
  IFS=',' read -r -a group_array <<< "$groups"
  for group in "${group_array[@]}"; do
    group=$(echo "$group" | xargs) # Remove leading and trailing whitespaces
    if [ -n "$group" ]; then
      if ! getent group "$group" &>/dev/null; then
        groupadd "$group"
        echo "Created group $group" | tee -a "$LOG_FILE"
      fi
      if id "$username" &>/dev/null; then
        usermod -aG "$group" "$username"
        if [ $? -eq 0 ]; then
          echo "Added $username to group $group" | tee -a "$LOG_FILE"
        else
          echo "Failed to add $username to group $group" | tee -a "$LOG_FILE"
        fi
      else
        echo "User $username does not exist to add to group $group" | tee -a "$LOG_FILE"
      fi
    fi
  done

done < "$INPUT_FILE"

echo "User creation process completed." | tee -a "$LOG_FILE"

Step 3: Making the Script Executable

You can make the script executable by running the following:

chmod +x create_users.sh

Step 4: Running the Script

You can only run the script with root permissions:

sudo ./create_users.sh

Step 5: Adding the Script to a Remote Repository

Initialize a Git Repository: git init

Add the Script: git add create_users.sh

Commit the Changes: git commit -m "commit message"

Add the Remote Repository: git remote add origin <remote_repository_url>

You can then push the Changes: git push origin main

Step 6: Testing the Script

Create a test environment by setting up a virtual machine and ensure you have root access.
Prepare the Input File: The users.txt file

ronke; sudo,dev,admin
charity; sudo
mosh; designer,admin

You have to make sure that the create_users.sh script is in the same directory as users.txt

Run the Script:

sudo ./create_users.sh

Check if the users were created:

getent passwd ronke charity mosh

Verify the groups each user belongs to:

groups ronke charity mosh

Confirm the home directories were created with the correct permissions:

ls -ld /home/ronke /home/charity /home/mosh

Check the log file for actions performed by the script:

cat /var/log/user_management.log

Ensure passwords are stored securely:

sudo cat /var/secure/user_passwords.txt

Conclusion

This script allows SysOps engineers to efficiently manage employees' usernames and group names, ensuring security and consistency.

To learn more about the HNG program, visit the HNG Internship websites:

Automating User and Group Creation with a Bash Script