Introduction
In the world of a SysOps engineer, one of the common tasks you will encouter is the creation and management of users and groups. Automation helps simplify this process, making it efficient and time saving. In this blog post, we'll go through a bash script createusers.sh that automates the creation of users and groups, set up home directories with appropriate permissions and ownership, generate random passwords for the users, and log all actions.
Breaking down the script
Here is the complete script created in create_users.sh with and an explanation of each section.
#!/bin/bash # Define the log & password file variables LOG_FILE="/var/log/user_management.log" PASSWORD_FILE="/var/secure/user_passwords.csv" # Create and set permissions for log and password files touch $LOG_FILE mkdir -p /var/secure touch $PASSWORD_FILE chmod 600 $PASSWORD_FILE # Generate a random password for a user generate_password() { tr -dc A-Za-z0-9 </dev/urandom | head -c 12 } # Check if the file is provided if [ -z "$1" ]; then echo "Usage: $0 <user_file>" exit 1 fi USER_FILE="$1" # Process each line of the user file while IFS=";" read -r username groups; do # Remove leading and trailing whitespace from username and groups username=$(echo $username | xargs) groups=$(echo $groups | xargs) # If a user does not exist, create user and personal group if ! id -u $username >/dev/null 2>&1; then useradd -m -s /bin/bash $username echo "$(date) - Created user: $username" >> $LOG_FILE # Generate a password for the user password=$(generate_password) echo "$username,$password" >> $PASSWORD_FILE echo "$username:$password" | chpasswd # Set appropriate permissions and ownership for home directory chown -R "$username:$username" "/home/$username" chmod 700 "/home/$username" # Assign the user to the specified groups if [ -n "$groups" ]; then IFS=',' read -r -a group_array <<< "$groups" for group in "${group_array[@]}"; do if ! getent group $group >/dev/null; then groupadd $group echo "$(date) - Created group: $group" >> $LOG_FILE fi usermod -aG $group $username echo "$(date) - Added $username to group: $group" >> $LOG_FILE done fi else echo "$(date) - User $username already exists" >> $LOG_FILE fi done < "$USER_FILE" echo "The user creation process is completed." Explanation
Defining the log & password file variables: We define the paths for the log file and the password storage file. It also ensures that a secure directory for password storage is created with the neccesary permissions.
LOG_FILE="/var/log/user_management.log" PASSWORD_FILE="/var/secure/user_passwords.csv" touch $LOG_FILE touch $PASSWORD_FILE chmod 600 $PASSWORD_FILE Processing the Input File: The script reads the input file provided. Each line is expected to have a username and a list of groups separated by a semicolon. The script processes each line, removing any leading or trailing whitespace from username and groups.
if [ -z "$1" ]; then echo "Usage: $0 <user_file>" exit 1 fi USER_FILE="$1" while IFS=";" read -r username groups; do # Remove leading and trailing whitespace from username and groups username=$(echo $username | xargs) groups=$(echo $groups | xargs) Generating Random Passwords: This script generates random passwords for each user using a secure method. These passwords are then stored in a directory; /var/secure/user_passwords.csv, with the neccesary file permissions set to ensure only the owner can read it.
generate_password() { tr -dc A-Za-z0-9 </dev/urandom | head -c 12 } Function to Create Users and Groups: This script creates each user and their group, as well as any additional groups. If the user or group already exists, the script logs a message and skips to the next entry. It sets up home directories with appropriate permissions and ownership.
if ! id -u $username >/dev/null 2>&1; then useradd -m -s /bin/bash $username echo "$(date) - Created user: $username" >> $LOG_FILE password=$(generate_password) echo "$username,$password" >> $PASSWORD_FILE echo "$username:$password" | chpasswd chown -R "$username:$username" "/home/$username" chmod 700 "/home/$username" if [ -n "$groups" ]; then IFS=',' read -r -a group_array <<< "$groups" for group in "${group_array[@]}"; do if ! getent group $group >/dev/null; then groupadd $group echo "$(date) - Created group: $group" >> $LOG_FILE fi usermod -aG $group $username echo "$(date) - Added $username to group: $group" >> $LOG_FILE done fi Running the Script
Before executing the script, ensure it has executable permissions. You can make it executable by granting the necessary permissions using:
chmod +x create_users.sh Run the Script with Root Privileges.
sudo ./create_users.sh After executing the script, it will display messages confirming the creation.
Conclusion
This bash script helps automate user creation and management making the process easier and saves time. This ensures all actions are logged and passwords stored securely.
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