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I'm using rsync to backup some of my files:

rsync -aEN --delete --link-dest="$CURR/" "$SOURCE/" "$NEW/"

The --link-dest option works fine with most files, but not with symlinks.
When I was writing a clean-up script for old backups, I noticed that unchanged symlinks are not hard-linked, but rather copied.

Now I'm wondering:
Is there a way to make rsync hard-link unchanged symlinks as well?
And if not: Is it intentional or a bug in rsync?

I'm using rsync version 3.1.1 on Mac OS 10.11.

Edit:

It seems to be a problem in Mac OS X. For some reason HFS+ seems not to support hard-links to symlinks.

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3
  • The --copy-links option is probably what you want. Commented Jun 17, 2016 at 14:33
  • I'm not sure you can create a hard link to a symbolic link... Commented Jun 17, 2016 at 15:43
  • Sure, you cannot. But the --copy-links option copies the files to which the links point (which is as close as OP will get to what was intended). Commented Jun 17, 2016 at 16:25

2 Answers 2

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The filesystem on macOS (HFS+) does not support hard links to symbolic links:

$ touch file $ ls -l file -rw-r--r-- 1 kk staff 0 Jun 17 18:35 file $ ln -s file slink $ ls -l file slink -rw-r--r-- 1 kk staff 0 Jun 17 18:35 file lrwxr-xr-x 1 kk staff 4 Jun 17 18:36 slink -> file

The following would ordinarily create a hard link to a symbolic link, and is even documented in the ln manual on macOS to do so (EDIT: no it isn't, unless you have GNU coreutils installed and read the wrong manual, doh!):

$ ln -P slink hlink $ ls -l file slink hlink -rw-r--r-- 1 kk staff 0 Jun 17 18:35 file lrwxr-xr-x 1 kk staff 4 Jun 17 18:38 hlink -> file lrwxr-xr-x 1 kk staff 4 Jun 17 18:36 slink -> file

You can see by the ref count (1) that no new name was created for slink (would have been 2 for both slink and hlink if it had worked). Also, stat tells us that hlink is a symbolic link with 1 inode link (not 2):

$ stat hlink File: 'hlink' -> 'file' Size: 4 Blocks: 8 IO Block: 4096 symbolic link Device: 1000004h/16777220d Inode: 83828644 Links: 1 Access: (0755/lrwxr-xr-x) Uid: ( 501/ kk) Gid: ( 20/ staff) Access: 2016-06-17 18:38:18.000000000 +0200 Modify: 2016-06-17 18:38:18.000000000 +0200 Change: 2016-06-17 18:38:18.000000000 +0200 Birth: 2016-06-17 18:38:18.000000000 +0200

EDIT: Since I was caught using GNU coreutils, here's the tests again with /bin/ln on macOS:

$ touch file $ /bin/ln -s file slink $ /bin/ln slink hlink # there is no option corresponding to GNU's -P $ ls -l file slink hlink -rw-r--r-- 2 kk staff 0 Jun 17 18:59 file -rw-r--r-- 2 kk staff 0 Jun 17 18:59 hlink lrwxr-xr-x 1 kk staff 4 Jun 17 18:59 slink -> file

The hard link is pointing to file rather than to slink.

On e.g. Linux and OpenBSD (the other OSes I use), it is possible to do this, which results in

$ ls -l file slink hlink -rw-rw-r-- 1 kk kk 0 Jun 17 18:35 file lrwxrwxrwx 2 kk kk 4 Jun 17 18:43 hlink -> file lrwxrwxrwx 2 kk kk 4 Jun 17 18:43 slink -> file

(notice "2")

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    That answers my question, thank you. Puzzles me why it isn't implementet, considering even hard-linking directories is implemented in HFS+. Commented Jun 17, 2016 at 17:36
  • Yeah, I thought that fact was a bit humorous too. Commented Jun 17, 2016 at 17:40
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You cannot make hardlinks to symbolic links (this is not a "limitation" of OS X). A hardlink is a reference to an inode, and a symbolic link is not an inode but only an entry in the directory with some additional information.

You may be thinking of Windows, which has analogous features, which behave differently.

rsync does have a --copy-links option which tells it to copy the file to which a symbolic link points to the destination. That would be useful if you are trying to construct a complete replica of your source directory (but not very useful if your goal is to reduce disk usage).

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  • I believe you're wrong. See my answer. Commented Jun 17, 2016 at 16:47
  • 1
    My bad. It turns out I had the GNU coreutils installed. That's where that manual comes from. Still, I can create a hard link to a symbolic link on other OSes... Commented Jun 17, 2016 at 16:56
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    It's a recent feature in POSIX, which doesn't appear to be documented for OSX. rsync isn't in POSIX, doesn't have to support new features. Commented Jun 17, 2016 at 17:02
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    I don't see why it shouldn't be possible to create hard-links to symlinks. Anyway I just tested it on Linux and it worked fine. As for Windows, I don't know what features it offers. I've avoided it for the last 14 or so years. Commented Jun 17, 2016 at 17:11
  • 1
    It depends. The rsync program takes it into account (see log entry). Commented Jun 17, 2016 at 17:24

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