Backup Solution thoughts...

[Philip Mak]

I'm thinking of how to backup an entire server ("server A") to a
remote area ("server B") using rsync.

My initial thought was to have a shell account on server B, then have a
cronjob running as root on server A that uses rsync to send all the files
over to the shell account on server B.

Then I thought that this is not reliable against hackers, because if
someone hacked the machine, he can find the cron job, get the password to
the shell account on server B, and delete that backup.

So, it sounds like server B should be the one with the cron job,
synchronizing with server A.

My question is: How can I make server A give READ-ONLY rsync access of the
entire disk to server B?