rsync - a fast, versatile, remote (and local) file-copying tool
–rsync man page
As the man page suggests, rsync is a useful tool if you’re tired of
cp-ing files around servers and managing the disastrous permissions aftermath. It has the ability to manage permissions, compress on-the-fly, and doesn’t waste time copying things that already exist in the destination.
#Rsync is Smart
Let’s say you have two folders,
folder2. These folders contain a very large amount of data, and right now they are the exact same. But let’s say you make a small change to
folder1, like maybe adding a small file, or fixing a typo somewhere.
Without rsync, to ensure
folder2 still contains an accurate copy, you have a couple options:
- Manually change
folder2the same way you did to
folder1. To do this, you’d have to remember exactly what you did to
folder1each time you make a change. What happens when you have 4 or 5, or 100 copies of this folder? Assuming you had perfect memory and a lot of time, this solution still isn’t perfect, because the modification times on the files would be different.
folder1. This would work, if the folders were small– but for our example, they’re not.
cp-ing this folder could take hours.
Rsync is smart in that it only copies changes to your files. If we added
folder1 and ran rsync, it would only add
folder2 and call it a day- no need to re-copy the existing accurate files.
#Example Use Case: Copying Music
I run an Airsonic music server, which holds the “master copy” of some music I listen to. However, I prefer to keep local copies of this music on some of my machines, and so I find myself constantly having to keep all versions of this music the same across all my machines and server.
What about Git? Git is a version control system that would appear to solve this problem of concurrency; however, git works poorly for this use case.
With a single
rsync command on each machine, I can pull down changes to the music folder to my local copy. This way, the copy on the server is the only one I have to manage.
rsync --delete --recursive --compress --verbose email@example.com:/remote/music/ /local/music/
Rsync is a versatile tool, and has a ton of capabilities I didn’t cover in this introduction.
man rsync covers these and more.