As part of the requirements of my DevOps internship with HNG, I am required to create a bash script to automate user management.
Managing users in a Linux environment can be a repetitive and error-prone task if done manually, especially when dealing with a large number of users. To simplify this process, you can use a bash script to automate user creation, group assignment, and password management. Let’s walk through a comprehensive bash script designed to streamline user management. This script reads a list of usernames and groups from a text file, creates users and groups accordingly, sets up home directories, generates random passwords, and logs all actions for audit purposes. You can find the complete script on my GitHub repository.
This bash script performs several key tasks:
Ensures root privileges: The script checks if it is run as root.
Logs actions: Logs important actions and errors for audit and debugging.
Validates inputs: Ensures usernames and group names are valid.
Creates users and groups: Adds new users and groups as specified in an input file.
Sets passwords: Generates and sets random passwords for new users.
Configures home directories: Sets appropriate permissions for user home directories.
Detailed Explanation of script.
Script Header and Logging
The script begins by defining a logging function to record actions and errors to a log file.
log() {
echo “$(date ‘+%Y-%m-%d %H:%M:%S’) – $1” >> “$LOG_FILE”
}
Password Generation
A function to generate random passwords is defined, which uses /dev/urandom for secure random number generation.
local password_length=12
tr -dc A-Za-z0-9 </dev/urandom | head -c $password_length
}
Ensuring Root Privileges
The script checks if it is run with root privileges. If not, it logs an error and exits. Root users have user id 0.
echo “This script must be run as root or with sudo privileges” >&2
log “Script not run as root or with sudo privileges”
exit 1
fi
File Paths and Initial Checks
The script sets file paths for the user input file, log file, and password storage. It also verifies the existence of these files.
LOG_FILE=”/var/log/user_management.log”
PASSWORD_FILE=”/var/secure/user_passwords.txt”
if [ -z “$USER_FILE” ]; then
echo “Usage: $0 <name-of-text-file>”
log “No user file provided. Usage: $0 <name-of-text-file>”
exit 1
fi
if [ ! -f “$USER_FILE” ]; then
echo “Input file not found”
log “Input file ‘$USER_FILE’ not found”
exit 1
fi
if [ ! -f “$LOG_FILE” ]; then
touch “$LOG_FILE”
chmod 0600 “$LOG_FILE”
log “Log file created: $LOG_FILE”
fi
if [ ! -f “$PASSWORD_FILE” ]; then
mkdir -p /var/secure
touch “$PASSWORD_FILE”
chmod 0600 “$PASSWORD_FILE”
log “Password file created: $PASSWORD_FILE”
fi
Input Validation
The script validates the usernames and group names using regular expressions to ensure they contain only alphanumeric characters, hyphens, and underscores.
if [[ ! “$1” =~ ^[a-zA-Z0-9_-]+$ ]]; then
return 1
fi
return 0
}
validate_groups() {
IFS=’,’ read -ra group_list <<< “$1”
for group in “${group_list[@]}”; do
if [[ ! “$group” =~ ^[a-zA-Z0-9_-]+$ ]]; then
return 1
fi
done
return 0
}
User and Group Creation
The script reads the user file line by line, creating users and their groups as necessary. It also ensures that each user has a personal group and sets up the home directory with appropriate permissions.
username=$(echo “$username” | xargs)
groups=$(echo “$groups” | xargs)
if [ -z “$username” ] || [ -z “$groups” ]; then
log “Invalid line format in user file: ‘$username;$groups'”
user_creation_failed=true
continue
fi
if ! validate_username “$username”; then
log “Invalid username format: ‘$username'”
user_creation_failed=true
continue
fi
if ! validate_groups “$groups”; then
log “Invalid group format: ‘$groups'”
group_creation_failed=true
continue
fi
if id “$username” &>/dev/null; then
log “User $username already exists.”
continue
fi
all_users_exist=false
if ! getent group “$username” > /dev/null; then
if groupadd “$username”; then
log “Group $username created.”
else
log “Failed to create group $username.”
group_creation_failed=true
continue
fi
fi
IFS=’,’ read -ra group_list <<< “$groups”
for group in “${group_list[@]}”; do
if ! getent group “$group” > /dev/null; then
if groupadd “$group”; then
log “Group $group created.”
else
log “Failed to create group $group.”
group_creation_failed=true
fi
fi
done
unset IFS
if useradd -m -g “$username” -G “$groups” “$username”; then
log “User $username created and added to groups $groups”
users_created=true
any_users_created=true
else
log “Failed to create user $username”
user_creation_failed=true
continue
fi
password=$(generate_password)
log “Generated password for $username”
if echo “$username:$password” | chpasswd; then
echo “$username,$password” >> “$PASSWORD_FILE”
log “Password set for $username and stored securely”
else
log “Failed to set password for $username”
password_setting_failed=true
continue
fi
if chown “$username:$username” “/home/$username” && chmod 700 “/home/$username”; then
log “Home directory for $username set up with appropriate permissions.”
else
log “Failed to set up home directory for $username”
home_directory_setup_failed=true
fi
done < “$USER_FILE”
Summary and Exit
After processing all lines, the script logs a summary of the actions taken and exits.
if [ “$any_users_created” = true ]; then
echo “$(date ‘+%Y-%m-%d %H:%M:%S’) – User creation script completed successfully.”
elif [ “$all_users_exist” = true ]; then
echo “Users already exist. Nothing left to do”
else
echo “$(date ‘+%Y-%m-%d %H:%M:%S’) – No users were created successfully. Check log file.”
log “No users were created successfully. Please check the input file format: username;group1,group2,group3.”
fi
[ “$user_creation_failed” = true ] && echo “Users creation incomplete.” && log “Some users were not created due to errors. Check file format”
[ “$password_setting_failed” = true ] && echo “Users’ passwords creation incomplete.” && log “Some users’ passwords were not set due to errors. Check file format”
[ “$group_creation_failed” = true ] && echo “Groups creation incomplete.” && log “Some groups were not created due to errors. Check file format”
[ “$home_directory_setup_failed” = true ] && echo “Home directories creation incomplete.” && log “Some home directories were not set up due to errors.”
exit 0
Conclusion
This script offers a reliable way to automate processes related to user management, lowering the possibility of mistakes and saving important administrative time. System administrators can create user accounts in a consistent and safe manner with this script, which also manages passwords and group assignments. Detailed logs are kept for accountability and debugging purposes. To get real-time internship experience, sign up with HNG
