NFS exports might not be the technology you want to use. If it's possible, I'd setup an rsync script, because that will let you preserve user permissions, directory structure, time stamp, and let you resume partial backups, and it's much easier to set it up on a timer via a cron script--it takes about 20 minutes to learn how to use and script with so it's really a good time investment. I was in a shop that did NFS exports for a while only to find the backups weren't always viable and only had about a 70% success rate for a usable nightly backup. When we switched over to rsync, we would only get one bad backup every two months.
NFS just backs things up based on the Unix User ID in /etc/passwds (or whatever PAM authentication module you're using, so you'd really need to setup NIS in your house for this to work properly) on the host machine. If the user doesn't exist, it will preserve the user id and permissions by default, but if that user/group doesn't exist on the server hosting the backup, then you won't have read-write permissions to restore it.