Restricting Superuser (Root) Access

In general, superuser is not allowed root access to file systems shared across the network. Unless the server specifically grants superuser privileges, a user who is logged in as superuser on a client cannot gain root access to files that are remotely mounted on the client. The NFS system implements this by changing the user ID of the requester to the user ID of the user name, nobody; this is generally 60001. The access rights of user nobody are the same as those given to the public (or a user without credentials) for a particular file. For example, if the public has only execute permission for a file, then user nobody can only execute that file.

An NFS server can grant superuser privileges on a shared file system on a per-host basis, using the root=hostname option to the share command.