Symptom
If you create a user named "root" in the Setup Assistant or Users control panel, you may encounter unforeseen difficulties caused by a conflict between two "root" user accounts.
When setup assistant creates the first user account it is created with a specific numeric user ID. This ID is different from the built in 'root' account and conflicts can arise if two 'root' accounts exist.
Solution
Do not use the name "root." Pick a different name for the user account.
The name "root" is reserved for system use in UNIX-like operating systems. Conflicts between the operating system's root user and your "root" user can arise if you choose this name.