User Management in Linux using a bash script

Managing users on Linux systems can be daunting, especially in environments with frequent changes. As part of my online internship at https://hng.tech/internship, I've been assigned a task to develop a Bash script to automate this process. Let's dive into how this script works:

1. Initial Setup

# Check if script is run with sudo
if [ "$(id -u)" != "0" ]; then
    echo "This script must be run with sudo. Exiting..."
    exit 1
fi

# Redirect stdout and stderr to log file
exec > >(tee -a "$LOG_FILE") 2>&1 
echo "Executing script... (note that this line will be logged twice)" | tee -a $LOG_FILE 

2. Input Validation

# Check if an argument was provided
if [ $# -eq 0 ]; then
    echo "No file path provided." 
    echo "Usage: $0 <user-data-file-path>" 
    exit 1
fi

# Check if the user's data file exists
if [ ! -e "$USERS_FILE" ]; then
    echo "The provided user's data file does not exist: $USERS_FILE"
    exit 1
fi

3. Dependency Management

# Function to check if a package is installed
is_package_installed() {
    dpkg -s "$1" >/dev/null 2>&1
}

# Check if openssl is installed
if ! is_package_installed openssl; then
    echo "openssl is not installed. Installing..."
    sudo apt-get update
    sudo apt-get install -y openssl
fi

# Check if pwgen is installed
if ! is_package_installed pwgen; then
    echo "pwgen is not installed. Installing..."
    sudo apt-get update
    sudo apt-get install -y pwgen
fi

4. File and Directory Management

# Create the directory where the user's password file will be stored
sudo mkdir -p "$PASSWORD_FILE_DIRECTORY"

# load the content of the users.txt file into an array: lines
mapfile -t lines < "$USERS_FILE"

5. User Creation and Management

# loop over each line in the array
for line in "${lines[@]}"; do
    # Remove leading and trailing whitespaces
    line=$(echo "$line" | xargs)

    # Split line by ';' and store the second part
    IFS=';' read -r user groups <<< "$line"

    # Remove leading and trailing whitespaces from the second part
    user=$(echo "$user" | xargs)
    groups=$(echo "$groups" | xargs)

    # Check if user exists
    if id "$user" &>/dev/null; then
        echo "User $user already exists. Skipping creation."
        continue
    fi

6. Password Handling

# Generate a 6-character password using pwgen
password=$(pwgen -sBv1 6 1)

# Encrypt the password before storing it
encrypted_password=$(encrypt_password "$password" "$PASSWORD_ENCRYPTION_KEY")

# Store the encrypted password in the file
echo "$user:$encrypted_password" >> "$PASSWORD_FILE"

7. User and Group Operations

# Create the user with the generated password
sudo useradd -m -p $(openssl passwd -6 "$password") "$user"

# Set Bash as the default shell
set_bash_default_shell "$user"

# loop over each group in the groups array
for group in "${groupsArray[@]}"; do
    group=$(echo "$group" | xargs)

    # Check if group exists, if not, create it
    if ! grep -q "^$group:" /etc/group; then
        sudo groupadd "$group"
        echo "Created group $group"
    fi

    # Add user to the group
    sudo usermod -aG "$group" "$user"
    echo "Added $user to $group"
done

8. Conclusion and Cleanup

# remove the created password from the current shell session
unset password

After completing this task and the follow-up tasks to stage 10 in the internship, I believe I will be ready for the job market in the DevOps field. If you are a hiring manager reading this article, you can get exceptional talent here https://hng.tech/hire. Thank you for reading my article.

Author: Ambrose Onsare