Hacker News Reader

Comment by nixcraft | Hacker News Reader

rsnapshot[1] is what I used on FreeBSD with a snapshot. It is like a well-tested version of the author's rsync and ssh blog post. I have a blog post here[2] describing my setup. It saved my bacon multiple times. Also, rsnapshot works in pull mode, so no client is needed on my Linux/macOS desktop or server except ssh and rsync.

[1] https://github.com/rsnapshot/rsnapshot [2] https://www.cyberciti.biz/faq/howto-install-rsnapshot-filesy...

View on HN

Tangential question: I've been using rsnapshot to backup a remote machine to my local NAS for a while now. My impression is that even for an incremental backup, everything that I want to have backed up is transferred over the wire, and it is determined locally what actually needs to be written to disk, and what can be hardlinked from a previous backup. Is there a way to configure rsnapshot so that it only transfers the data that's actually changed?

That is the default. rsnapshot uses rsync between local and remote, and rsync uses delta encoding algo so it is speedy. You may need to tune your ssh, networking stack and rsync.

Yep. We use rsnapshot with btrfs snapshots on Debian / Ubuntu. You can set up multiple generations easily. Efficient storage using hard links.

Very reliable.

AFAIK the crucial part of this, is rsync's `--link-dest=DIR` parameter, which hard-links an unmodified file to the respective place in "DIR", rather than making a copy.

The docs for my version of rsnapshot say not to use '--link-dest' if GNU cp is available, because the script will use 'cp -l' instead when copying "daily-1" to "daily-0" (for example). This is before it will overwrite "daily-0" with new files via rsync.

Could you elaborate on where the btrfs snapshots come into play? I use rsnapshot on a plain ext4 fs and it’s pretty slow (lots of small files).

The snapshots don't help with the speed.

Instead, they make sure the files aren't changing / being deleted between when the rsync starts and finishes.

Reply on news.ycombinator.com