What Is It?
Rsync is an intelligent, block-based, file transfer and synchronisation program which is very effective at minimizing the amount of data transferred between systems. It features delta encoding and so transmits only the portions of a file that have changed since the last exchange.
How did it come about?
Rsync was written by Andrew "Tridge" Tridgell, sometime in 1996. At the time he was working on Samba and needed a way of keeping his source trees in-sync on his university and home accounts.
Where would I use it?
Rsync is one of those versatile utilities that can be used for hundreds of tasks, we find ourselves implementing projects with rsync whenever we need to:
- Distribute updated configurations from a central master host
- Gather distributed logfiles from a numbers of remote hosts or IDS sensors
- Perform remote backups securely, especially where bandwidth is constrained
- Archive file checksums and signatures somewhere safe
Why is it so good?
If you are still wondering why an automated file transfer and synchronisation utility is on a list of security software, you havent had to run a network of systems in a large enterprise, or come into contact with Intrusion Detection Systems, or anything resembling a loghost. Moving files around a large organisation with internal Firewalls is a pain, but its something you can ease with rsync.
- It can provide secure transfer of files through full support for ssh, mentioned elsewhere
- Rsync is cross platform, and can be deployed on Windows, UNIX, and most other systems
- It is very efficient in terms of network bandwidth, meaning housekeeping jobs often finish in a fraction of the time you current allow.
- It is highly tunable, so can be tweeked to use large block sizes
- Rsync is easy to automate securely
- Rsync can be triggered in a way that does not conflict with your organisations security policy, e.g. outside-to-inside access, push versus pull, etc.
Who uses it?
Rsync.Net have built an entire backup service using it. Fermilab, generate vast amounts of data to store and move around. BP, a highly distributed large organisation, uses rsync across a mixture of fixed line, satellite, and other links in remote regions.
Where do I start?
Introduction 
