How to find all URI's & subdomains reserved by my server

[Morthian]

My website allows members to access their profiles by simply entering their username as the URI. (e.g. http://website.com/username)

In order to do this, I must restrict users from creating usernames that are identical to URI's reserved by the server. (e.g. cpanel)

Where can I find a list of URI's reserved by the server so that I can properly disallow all usernames that are reserved URI's?

In addition, where can I find a list of subdomains reserved by the server?

[logic_earth]

There are no reserved URIs....
Only those that you have folders/files in the public root.

[Morthian]

I believe I am using the wrong term here. Thank you for pointing that out. Whatever the term may be, I am referring to the part of the URL directly after the domain. (http://website.com/cpanel)

'cpanel' is reserved, as it redirects to the site's cpanel.

I am certainly no expert of these sort of issues, so if the question seems difficult to understand, please let me know.