Documentation: create_user_with_permissions.sh

Purpose

The create_user_with_permissions.sh script is designed to:

1. Create a new user with:
   • A home directory.
   • The default Bash shell.
2. Set permissions such that:
   • The new user cannot access the files or directories of the main user.
   • The main user has full access to all files and directories of the new user.
3. Synchronize the contents of the Example directory from the main user's home directory to the new user's Example directory. Any existing files in the new user's Example directory are replaced with those from the main user.

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Key Features

• Flexible User Specification: Allows dynamic specification of the new user and the main user as command-line arguments.
• Permission Management:
  • Ensures that the new user's files are private except for access granted to the main user.
  • Restricts the new user from accessing any files or directories of the main user.
• Example Directory Synchronization:
  • Uses the rsync command to copy files efficiently, preserving file attributes and metadata.
  • Ensures the new user's Example directory is an exact replica of the main user's Example directory.

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Script Overview

Input Arguments:

• <new_user>: The username for the new user to be created.
• <main_user>: The existing username with permissions to access the new user's files.

Functions:

• usage: Displays usage information and exits if the arguments are incorrect.
• create_new_user: Creates the new user, sets up their home directory and bash shell, and configures permissions for file access.
• sync_Example_directory: Copies or replaces all files in the new user's Example directory with those from the main user's Example directory, ensuring proper ownership and permissions.

Error Handling:

• Verifies that both the new user and main user are valid.
• Checks if the main user's Example directory exists before attempting to synchronize.

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Tasks Performed

1. User Creation:

   • Creates the new user using useradd with options to generate a home directory and use the bash shell.
   • Ensures user-specific permissions:
     • New user has private access to their home directory (chmod 755).
     • Main user is granted full access to the new user's home directory via setfacl.

2. Example Directory Synchronization:

   • Replaces all files in the new user's Example directory with those from the main user's Example directory.
   • Ensures the new user's Example directory has proper ownership and permissions (chown).

3. Post-Synchronization State:

   • The new user's Example directory is a replica of the main user's Example directory.
   • Main user retains full access to the new user's home directory.

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How to Use

1. Save the script as create_user_with_permissions.sh.
2. Make the script executable:

   chmod +x create_user_with_permissions.sh

3. Run the script as a superuser (with sudo), specifying the new user and the main user:

   sudo bash create_user_with_permissions.sh <new_user> <main_user>

   Example:

   sudo bash create_user_with_permissions.sh newuser mainuser

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Requirements

• Operating System: Ubuntu-based systems.
• Permissions: The script must be executed with superuser privileges (sudo).
• Preconditions:
  • The main user must already exist on the system.
  • The new user must not already exist on the system.

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Example Use Case

1. Command:

   sudo bash create_user_with_permissions.sh developer admin

2. Outcome:
   • A new user developer is created.
   • The admin user is granted full access to developer's files.
   • All files from /home/admin/Example are copied to /home/developer/Example, overwriting existing files in developer's Example directory.

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Notes

• Ensure that the Example directory in the main user's home contains the desired files before running the script.
• The script performs a complete replacement of files in the new user's Example directory, so any pre-existing files will be deleted.

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Contributing

If you'd like to improve this script, you can:

1. Fork the repository containing the script.
2. Make your changes.
3. Submit a pull request with a description of the improvements.

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License

This script is licensed under the MIT License. You can view the full text of the MIT License here.