You can have root access only on VPS and Dedicated accounts. Basically its the master admin on Linux (God mode). Username is always root so you need to send the developer just the password. This allows them to see and modify EVERYTHING on the server so be very careful who are you giving your root password to. Some hosts don't use root account instead they use keys to login (more secure since you don't enter the password) and because there are two keys etc... also some hosts (managed ones) don't want to give root password since you may fuck something up and then it's their problem to fix that... For most programmers its really not needed unless you need some server work (hardening, optimizations etc...)... For most of the scripts and site work FTP and MySQL passwords are enough....
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