Can I hard link files with rsync instead of copying them?

Question

cp -l hard links files instead of copying them, saving filesystem space. I need to use rsync instead of cp because of its --exclude capabilities.

So my question is, how do I get rsync to hard link files instead of copying them? Obviously, this is a local filesystem copy. I've read the docs for rsync's -H option, but it's unclear to me if this behaves the same way as cp -l.

Solution 1

The answer has turned out to be yes, with rsync's --link-dest option. It's just not obvious because it's not a simple on/off flag like cp -l, because it takes a path argument.

So, cp -l a/ b/ can also be done like this:

rsync -a --link-dest=a a/ b/

Solution 2

I've been using https://github.com/rsnapshot/rsnapshot for a long time. It does exactly what you are describing.

Comments

[Admin]

It looks like I can get this behavior with --link-dest=$SOURCE_DIR: slaptijack.com/system-administration/… I'm testing this out now.

[Admin]

Generally, rsync is used for back-up or archive purposes. Why would you want a back-up of file names without their contents?

[Admin]

@AFH my backup script creates rolling backups of gigabytes of data at many points in time, but most of this data is the same. I save disk space by copying these between time points with cp -al. Without using hardlinks, all these different copies of data (if they were real files) wouldn't fit on my 2TB drives. See: slaptijack.com/system-administration/…

[Admin]

So you can recover from accidental deletions, thought not overwrites, but you'll never be able to use your back-up to recover from a disc failure or partition loss. I use cp -au, which copies only changed files, so the process doesn't take too long, but it does give me an external copy of the latest version of every file for recovery purposes. Of course, to back up Gigabytes of data you need Gigabytes of storage, but if your files are important you need to make that investment. Only unimportant files are not backed up, by definition.

[Yaroslav Nikitenko]

Did you try this command yourself? The man page says that --link-dest option, if relative, is relative to the target directory. This answer is more correct: serverfault.com/a/210058/251416

[Edward Falk]

I tried it out; you're right. @nnyby would want to do rsync -a --link-dest=../a a/ b/

[Sridhar Sarnobat]

My rsnapshot job seems to be creating full copies (ie different inodes). And my free space is going down by non-trivial amounts. Any idea what I'm missing?

[jw013]

@SridharSarnobat Check your rsnapshot config file and make sure you have the link dest feature enabled.