rsync is a free software computer program for Unix and Linux like systems which synchronizes files and directories from one location to another while minimizing data transfer using delta encoding when appropriate. An important feature of rsync not found in most similar programs/protocols is that the mirroring takes place with only one transmission in each direction. This tool is very appropriate to keep backup or setup mirror service. In this article you will get some clear idea.
Perform rsync asks for password on the remote server before starting the transfer. Sometimes we need to run rsync by crontab where it is not possible to give password. Here is a solution to use crontab to execute rsync without any password.
This is helpful when you are scheduling a cron job for automatic backup using rsync.