Automating User and Group Management with Shell Scripts

Managing users and groups in a Linux environment can be a tedious task, especially in larger systems. Automation of these tasks not only saves time but also minimizes errors. In this article, we will explore two shell scripts that automate the creation and deletion of users and groups based on a predefined list. This article is structured to provide a clear understanding of the steps involved and the reasoning behind each step.

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Table of Contents

1. Introduction

2. Script Overview

3. Detailed Explanation

4. Example Usage

5. Conclusion

6. Learn More About HNG Internship

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Introduction

User and group management is a critical aspect of system administration. It involves creating, modifying, and deleting user accounts and groups, as well as managing permissions and access controls. Automating these tasks can significantly improve efficiency and reduce the likelihood of human errors.

In this article, we will discuss two scripts:

1. create_users.sh - A script to create users and groups.

2. delete_users.sh - A script to delete users and groups.

Both scripts take a text file (users.txt) as input, which contains the usernames and groups in a specific format.

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Script Overview

create_users.sh

This script reads the users.txt file, creates users, assigns them to the specified groups, and generates a random password for each user. It logs all actions to a log file and saves the generated passwords to a secure file.

Here is the create_users.sh script:

#!/bin/bash

# Script to create users and groups from a text file
# Usage: ./create_users.sh users.txt

USER_FILE=$1

# Check if file is provided and exists
if [[ -z "$USER_FILE" || ! -f "$USER_FILE" ]]; then
  echo "Usage: $0 <user_file>"
  exit 1
fi

LOG_FILE="/var/log/user_management.log"
PASSWORD_FILE="/var/secure/user_passwords.csv"

# Ensure the log and password directories and files exist
mkdir -p /var/log
touch "$LOG_FILE"
mkdir -p /var/secure
touch "$PASSWORD_FILE"
chmod 600 "$PASSWORD_FILE"

# Function to generate a random password
generate_password() {
  openssl rand -base64 8
}

# Log action
log_action() {
  echo "$(date '+%Y-%m-%d %H:%M:%S') - $1" | tee -a "$LOG_FILE"
}

# Loop through each line in the user file
while IFS=';' read -r username groups; do
  username=$(echo "$username" | xargs) # Trim whitespace
  groups=$(echo "$groups" | xargs)     # Trim whitespace

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

  # Create personal group for the user
  if ! getent group "$username" &>/dev/null; then
    groupadd "$username"
    if [[ $? -eq 0 ]]; then
      log_action "Group $username created."
    else
      log_action "Failed to create group $username. Command output: $(groupadd "$username" 2>&1)"
      continue
    fi
  fi

  # Create additional groups if they do not exist
  IFS=',' read -ra group_array <<< "$groups"
  for group in "${group_array[@]}"; do
    group=$(echo "$group" | xargs) # Trim whitespace
    if ! getent group "$group" &>/dev/null; then
      groupadd "$group"
      if [[ $? -eq 0 ]]; then
        log_action "Group $group created."
      else
        log_action "Failed to create group $group. Command output: $(groupadd "$group" 2>&1)"
        continue 2
      fi
    fi
  done

  # Create user and add to groups
  password=$(generate_password)
  useradd -m -g "$username" -G "$groups" -s /bin/bash -p "$(openssl passwd -1 "$password")" "$username"
  if [[ $? -eq 0 ]]; then
    log_action "User $username created and added to groups: $groups"
    echo "$username,$password" >> "$PASSWORD_FILE"
    chmod 600 "$PASSWORD_FILE"
    chmod 700 "/home/$username"
    chown "$username:$username" "/home/$username"
  else
    log_action "Failed to create user $username. Command output: $(useradd -m -g "$username" -G "$groups" -s /bin/bash -p "$(openssl passwd -1 "$password")" "$username" 2>&1)"
  fi
done < "$USER_FILE"

log_action "User creation process completed."

delete_users.sh

This script reads the same users.txt file and deletes the users and their associated groups if they are no longer in use. It also logs all actions to the same log file.

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Here is the delete_users.sh script:

#!/bin/bash

# Script to delete users and groups from a text file
# Usage: ./delete_users.sh users.txt

USER_FILE=$1

# Check if file is provided and exists
if [[ -z "$USER_FILE" || ! -f "$USER_FILE" ]]; then
  echo "Usage: $0 <user_file>"
  exit 1
fi

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

# Log action
log_action() {
  echo "$(date '+%Y-%m-%d %H:%M:%S') - $1" | tee -a "$LOG_FILE"
}

# Loop through each line in the user file
while IFS=';' read -r username groups; do
  username=$(echo "$username" | xargs) # Trim whitespace
  groups=$(echo "$groups" | xargs)     # Trim whitespace

  # Delete user
  if id "$username" &>/dev/null; then
    userdel -r "$username"
    if [[ $? -eq 0 ]]; then
      log_action "User $username and their home directory deleted."
    else
      log_action "Failed to delete user $username. Command output: $(userdel -r "$username" 2>&1)"
    fi
  else
    log_action "User $username does not exist. Skipping."
  fi

  # Delete groups if empty
  IFS=',' read -ra group_array <<< "$groups"
  for group in "${group_array[@]}"; do
    group=$(echo "$group" | xargs) # Trim whitespace
    if getent group "$group" &>/dev/null; then
      if [[ -z "$(getent group "$group" | cut -d: -f4)" ]]; then
        groupdel "$group"
        if [[ $? -eq 0 ]]; then
          log_action "Group $group deleted."
        else
          log_action "Failed to delete group $group. Command output: $(groupdel "$group" 2>&1)"
        fi
      else
        log_action "Group $group not empty, skipping deletion."
      fi
    else
      log_action "Group $group does not exist. Skipping."
    fi
  done
done < "$USER_FILE"

log_action "User deletion process completed."

Detailed Explanation

Creating the users.txt File

The users.txt file should contain the list of users and their respective groups in the following format:

username;group1,group2,group3

For example:

adebola;developers
tobiloba;backend
dhebbie;developers
ayodeji;sudo,developers
balogun;admin
niyi;sudo,developers,admin
rasheed;frontend
bayo;frontend
shola;account
tope;account
rasak;backend
adedeji;developers
musty;technical

Each line specifies a username followed by the groups they should be added to, separated by commas.

Explanation ofniyi;sudo,developers,admin:

• niyi: The username.

• sudo: Adding niyi to the sudo group grants administrative privileges.

• developers: A custom group, usually for development-related tasks.

• admin: Another custom group for administrative purposes.

create_users.sh Script

The create_users.sh script performs the following tasks:

1. Checks if the input file is provided and exists.

2. Ensures the log and password directories and files exist.

3. Reads each line from the users.txt file.

4. Creates personal and additional groups for each user if they do not already exist.

5. Generates a random password for each user.

6. Creates the user and adds them to the specified groups.

7. Logs all actions and saves the generated passwords.

delete_users.sh Script

The delete_users.sh script performs the following tasks:

1. Checks if the input file is provided and exists.

2. Reads each line from the users.txt file.

3. Deletes each user and their home directory.

4. Deletes each group if it is empty.

5. Logs all actions.

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Example Usage

Running create_users.sh

chmod +x create_users.sh

sudo ./create_users.sh users.txt

Running delete_users.sh

chmod +x delete_users.sh

sudo ./delete_users.sh users.txt

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Conclusion

By automating the user and group management process with these scripts, you can streamline administrative tasks, improve efficiency, and ensure consistency across your systems. Feel free to modify the scripts to suit your specific requirements.

For more insights into DevOps practices and automation, check out the HNG Internship and HNG Premium programs. These programs offer excellent opportunities to learn, grow, and connect with other professionals in the industry.

You can access the scripts and related files on my GitHub repository for practice and further customization.

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By following the guidelines in this article, you can efficiently manage user and group creation and deletion, ensuring a streamlined and error-free system administration process. For more information and resources, explore the HNG Internship website and take advantage of the learning opportunities offered.