If you don't use the -m option when creating a user with the useradd command, the system will not create a home directory for that user. As a result, the user will not have a designated home directory where personal files and configurations can be stored.
Without a home directory, the user may encounter issues when trying to log in or run applications that expect a home directory to exist. Additionally, the user's environment may not be properly set up, leading to potential complications in managing user-specific settings and files.
In summary, omitting the -m option means the user will be created without a home directory, which can limit their functionality and usability.
