Automating User and Group Management using Bash Script

Creating users and groups manually particularly in a large environment can be time consuming and tedious. Automating this task with a bash script saves time and errors.
This script create_users.sh streamline the process, automates the creation of users and groups, sets up home directories, generates random passwords, and logs all actions. This article explains each step of the script and provides insights into its implementation.

Script Overview
The script reads a input file containing usernames and group names, creates users and groups as specified, sets up home directories with appropriate permissions and ownership, generates random passwords, and logs all actions. Additionally, it stores the generated passwords securely.

Prerequisites

• Basic understanding of Linux CLI and Bash Scripting.
• Ensure the script is run as root: Root privileges are necessary for creating users and groups. The script should be run using sudo.
• Provide an input file: The input file should contain usernames and group names separated by semicolons (;). Multiple group names should be comma-separated. Each user should be on a new line. For example:

glad;admin,devops
urunna;sysops
micah;architect,user 

Step-by-Step Explanation:
1. Checking Root Privileges
The script start by checking if it is run with root privileges. If not, it exits with an error message.

if [ "$(id -u)" -ne 0 ]; then
    echo "This script must be run as root" >&2
    exit 1
fi

2. Validating Input File
The script checks if an input file is provided and if it exists. If not, it exits with an error message.
USER_LIST=$1

if [ -z "$USER_LIST" ]; then
    echo "Usage: $0 <input_file>" >&2
    exit 1
fi

if [ ! -f "$USER_LIST" ]; then
    echo "Error: file not found: $USER_LIST" >&2
    exit 1
fi

3. Setting Up Log and Password Files
The script checks for the existence of the log and password files and creates them if they do not exist. It also sets appropriate permissions for the password file to ensure security.

LOG_FILE="/var/log/user_management.log"

if [ ! -f "$LOG_FILE" ]; then
    sudo touch "$LOG_FILE"
    echo "$LOG_FILE has been created."
else
    echo "Skipping creation of: $LOG_FILE (Already exists)"
fi

PASSWORD_FILE="/var/secure/user_passwords.txt"

if [ ! -d /var/secure ]; then
    sudo mkdir -p /var/secure
    sudo touch "$PASSWORD_FILE"
    sudo chmod 700 /var/secure
fi

4. Generating a Random Password
This function generates a random password using OpenSSL.

generate_password() {
    openssl rand -base64 12
}

5. Processing the Input File
This section reads the input file line by line, processes each username and group, creates the necessary groups, and adds the user to the specified groups. It also generates a random password for each user, sets up their home directory, and logs all actions.

while IFS=';' read -r username groups; do
    username=$(echo "$username" | xargs)
    groups=$(echo "$groups" | xargs)

    echo "Processing user: $username" | tee -a $LOG_FILE

    if ! getent group "$username" > /dev/null 2>&1; then
        sudo groupadd "$username"
        echo "Group $username created" | tee -a $LOG_FILE
    else
        echo "Group $username already exists" | tee -a $LOG_FILE
    fi

    group_array=()
    for group in $(echo "$groups" | tr ',' ' '); do
        group=$(echo "$group" | xargs)
        if getent group "$group" > /dev/null 2>&1; then
            group_array+=("$group")
        else
            echo "Invalid group name: $group" | tee -a $LOG_FILE
        fi
    done

    more_groups=$(IFS=','; echo "${group_array[*]}")

    if ! id -u "$username" > /dev/null 2>&1; then
        sudo useradd -m -g "$username" -G "$more_groups" "$username" &>/dev/null
        if [[ $? -eq 0 ]]; then
            echo "User $username created and added to groups: $more_groups" | tee -a $LOG_FILE

            password=$(generate_password)
            echo "$username:$password" | sudo chpasswd
            if [[ $? -eq 0 ]]; then
                echo "Password for $username set" | tee -a $LOG_FILE
                echo "$username,$password" >> $PASSWORD_FILE
            else
                echo "Failed to set password for user $username" | tee -a $LOG_FILE
            fi

            sudo chown "$username:$username" "/home/$username"
            sudo chmod 700 "/home/$username"
            echo "Home directory permissions set for $username" | tee -a $LOG_FILE
        else
            echo "Failed to create user $username" | tee -a $LOG_FILE
        fi
    else
        echo "User $username already exists" | tee -a $LOG_FILE
    fi

done < "$USER_LIST"

echo "User creation process completed. Logs can be found at $LOG_FILE.

Making the Script Executable
Before running the script, make sure it is executable. You can do this with the following command:
chmod +x create_users.sh

Running the Script
Now you can run the script with sudo:
sudo ./create_users.sh users.txt
This will ensure that the script reads from the provided user.txt file and performs the necessary user and group management tasks, logging actions to /var/log/user_management.logand storing passwords in /var/secure/user_passwords.txt.

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