NFS Server

Hi

I was going through the livefire NFS exercise and was confused by this
statement

Create this NFS share directory:

"/export/backup as read/writable limited by mounting by root user only"

This is through the NFS portion of the 3037 textbook, page 11-6

How do you limit it to be mounted by root user only? by altering the
/etc/export and doing this?

/export/backup root(rw)

root here is the name of the computer, so I am confused

WI