Syncing directories in both directions with rsync

Question

I happen to know about rsyn, and I use rsync to sync between my mac and a linux server as follows.

rsync -r -t -v MAC LINUX
rsync -r -t -v LINUX MAC

I expected to run the first command to sync, but I needed the second command also when a change is made in LINUX.

Am I missing something? Does rsync have an option to sync between two directories?

score 26 · Accepted Answer · edited May 05 '15 at 13:48

26

You want bi-directional sync. Take a look at unison, which does this: http://www.cis.upenn.edu/~bcpierce/unison/

For example, on Debian/Ubuntu:

$ sudo apt-get install unison
$ unison MAC/ LINUX/

If you have trouble with permissions (example ext4 -> FAT):

$ unison -perms 0 vlc-2.2.0/ /media/sf_vlc/vlc
Contacting server...
Looking for changes
Reconciling changes

vlc-2.2.0      vlc                
new dir  ---->            /  [f] 

Proceed with propagating updates? [] y
Propagating updates

edited May 05 '15 at 13:48

user1556814

103

answered Apr 28 '11 at 14:45

jmtd

9,305

If you use rsync and the devices have the same filesystems, you can sync all permissions. unison does not support this use-case. – MountainX Dec 06 '20 at 23:20

score 13 · Answer 2 · edited Dec 06 '20 at 23:18

13

It has been claimed that rsync was not recommended for two-way sync by its developers, but a source for this statement is lacking.

The already recommended unison utility will be a better solution for you.

Also keep in mind that you probably have to deal with a lot of Mac specific HFS+ stuff when using rsync. So be sure to use a properly patched rsync3 on the Mac or expect problems with modification dates (when using the Mac OS X provided rsync 2.6.9.) If you don't know how to build a properly patched rsync 3 for the Mac, get mlbackup which includes just that. (Full disclosure: I am the author of mlbackup.) Get it from github and be sure to download the full package from the downloads. (The mlbackup repo does not include rsync 3 which you want in this case.) http://github.com/MacLemon/mlbackup

edited Dec 06 '20 at 23:18

MountainX

17,948

answered Apr 28 '11 at 22:52

MacLemon

262

6

A link to the non-recommendation by rsync developers would be nice. – Wildcard Dec 14 '16 at 20:34
@Wildcard not from the developers, but this is relevant. – Jul 11 '18 at 03:17
@Ploni that page makes very limited use of rsync's features. I would not take it as definitive in regard to bidirectional sync with rsync. – MountainX Dec 06 '20 at 23:15
@MountainX you cannot use rsync for bidirectional synchronisation if you want to be able to propagate deletions either way – Chris Davies Dec 06 '20 at 23:51
@roaima Why not? I'm testing it and it seems to be working. What am I missing? – MountainX Dec 06 '20 at 23:55
Create a file. Synchronise. Delete the file. Synchronise. Watch it rise from the dead like a zombie – Chris Davies Dec 07 '20 at 00:04
@roaima Maybe you aren't using the necessary rsync options. I am able to sync two ways without dead files rising like zombies (but only after I sorted out the required options). – MountainX Dec 07 '20 at 01:49

score 5 · Answer 3 · answered Nov 15 '13 at 21:08

5

I coded this small tool for my own needs:

https://github.com/dooblem/bsync

It uses rsync and can handle file moves.

answered Nov 15 '13 at 21:08

Marc MAURICE

289

Thank you. I see you have committed a bug fix as recently as Mar 5, 2019. I will be giving your tool a try. – MountainX Dec 06 '20 at 23:01

score 5 · Answer 4 · answered Dec 04 '13 at 14:54

5

You should also take a look at csync, which is open source and offers native bi-directional syncing.

FYI - as far as I know - csync is developed by people from the Samba team. And knowing that the Samba team also developed rsync, I take this as a token of quality.

answered Dec 04 '13 at 14:54

maximd

121

Works for me, https://csync.org/userguide/, but the tool itself was discontinued in 2013 – Chris Davies Dec 06 '20 at 23:52

score 2 · Answer 5 · answered Jan 27 '13 at 11:00

2

Another excellent tool for bidirectional sync.....freefilesync

answered Jan 27 '13 at 11:00

rsjethani

287

5

on Stack Exchange, we prefer answers that are more than just links. it would be great if you could expand a little on what this is (what makes it different from unison?) – strugee Nov 15 '13 at 21:15
This project is a bit pushy in trying to get the users to make donations. Also, although source code is available. upstream does not host it on GitHub, GitLab or similar. – MountainX Dec 06 '20 at 23:08

score 2 · Answer 6 · answered May 05 '22 at 14:42

Another system that provides for synchronization of directories in both directions is SyncThing (Github) - "a continuous file synchronization program. It synchronizes files between two or more computers in real time, safely protected from prying eyes". There's also apps for mobile devices.

Syncing directories in both directions with rsync

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