rsync -Wav and hard links

Question

according to rsync command - MAN page:

#

-a, --archive This is equivalent to -rlptgoD. It is a quick way of saying you want recursion and want to preserve almost everything (with -H being a notable omission). The only exception to the above equivalence is when --files-from is specified, in which case -r is not implied.

Note that -a does not preserve hardlinks, because finding multiply-linked files is expensive. You must separately specify -H.

#

it's seems that we must use -H flag in order to copy also the hard links (realy?)

but according to my tests even if I not use the -H flag in rsync command the hard link copied successfully from local directory to other machine ? (very strange ?)

for example

ls -ltr

    -rw-r--r-- 1 root root 0 Jan 20 15:06 test.file.hard.link
    -rw-r--r-- 1 root root 0 Jan 20 15:06 test.file

    rsync -Wav   --progress /var/tmp/Backup_test_for_hard_link node1:/var/tmp

in node1 under /var/tmp I see the hard links files:

    -rw-r--r-- 1 root root 0 Jan 20 15:06 test.file.hard.link
    -rw-r--r-- 1 root root 0 Jan 20 15:06 test.file

please advice how it can be ?

Answer 1

Those two are not hardlinks, as the link count would have be 2 if they where indeed links.

Also, if a file was existant with two hard links and you don't use the -H option, rsync would just create two copies of the file, while the additional (expensive) logic of the -H option would recognize that the two files are in reality only one and recreate them accordingly.

To illustrate it:

Source dir (note the link count 2):

total 0
-rw-r--r-- 2 root root 0 Jan 20 13:37 myfile
-rw-r--r-- 2 root root 0 Jan 20 13:37 myfile2

Target dir after rsync -Wav --progress t1/* t2 (note the link count 1):

total 0
-rw-r--r-- 1 root root 0 Jan 20 13:37 myfile
-rw-r--r-- 1 root root 0 Jan 20 13:37 myfile2

Target dir after rsync -WavH --progress t1/* t3 (note the link count is 2 again):

total 0
-rw-r--r-- 2 root root 0 Jan 20 13:37 myfile
-rw-r--r-- 2 root root 0 Jan 20 13:37 myfile2