I have two computers (both MacBook Airs) for which I sync one directory tree in both, but not the entire hard drive or any other directories.

Let's say on computer A the directory is /Users/aellett/projects

Let's say on computer B the directory is /Users/bellett/projects

Generally, I'll log into computer B and then remotely connect to computer A as user 'aellett'. As super user I sync the two project directories as follows:

rsync -av /Volumes/aellett/projects/ /Users/bellett/projects/

and this works as expected.

On both computers I have another file letter.txt in a different directory which is not getting synced.

Let's say on computer A the file is found in /Users/aellett/letters

On computer B the file is found in /Users/bellett/correspondence

Generally, I don't want to share what's not included in /Users/<username>/projects. But I do want to share this particular file.

So on both computer I made a correspondence directory in projects. And then I made hard links as follows

On computer A:

ln /Users/aellett/letters/letter.txt   /Users/aellett/projects/correspondence/letter.txt

On computer B:

ln /Users/bellett/correspondence/letter.txt   /Users/aellett/projects/correspondence/letter.txt

The next time I synced the two computers I did the following

rsync -av -H /Volumes/aellett/projects/ /Users/bellett/projects/

When I checked on computer B, /Users/bellett/projects/correspondence/letter.txt was correctly synced. But, the hardlink to /Users/bellett/correspondence/letter.txt was no longer there. In other words, /Users/bellett/projects/correspondence/letter.txt was identical to /Users/aellett/projects/correspondence/letter.txt but it differed from /Users/bellett/correspondence/letter.txt. Since these two files were hard linked on both computers, I expected them to still have the hard link.

Why are my hard links not being preserved?