When you have root-level access to a server, it indicates that you'll have full control over it. In other words, you can set up any server-side app irrespective of the changes that it will make to the software setting on the server, and you'll be able to both access and modify any file, which includes system files, and modify any settings. This can be done by connecting to the server as a root user who has full privileges to perform all these things as well as to create other users, which includes users who also have full privileges. The connection can be established with a web-based graphical interface or a Secure Shell console. For safety reasons, it's recommended that you make a different user for your daily work and use the root user only when you need to customize the server or to set up software which may be required by a script-driven app that you'd like to run.