I am looking for a solution to sync folder pairs between a NAS and multiple local macs. Each of the macs could edit files and the other macs should then get synced automatically. Basically my own local version of Dropbox without using "cloud-storage".

I have looked into solutions using rsync. As I understand it rsync is not really capable of doing a bi-directional sync. I also do not want to necessarily invoke the sync process. I would prefer a daemon running in the background - waiting and checking for changes and then syncing them "live".

The program should also be flexible enough to recognize that it sometimes (in the case with laptops) can not reach the NAS. It should then just wait for the connection to be back again, without bugging me ever few minutes.

I have looked into synk, folderwatch, rsync, unison and a few others, but I haven't really found a solution. Either they need to be invoked or they are not really bi-directional.

Isn't there something like "offline folders" from microsoft for the mac?


PS: just for clarification - I don't want to sync for backup purposes, instead I am wanting to sync so that all macs have a local copy of the most recent changes to files.

  • possible duplicate of Alternative to Dropbox (on my server)? Jun 23 '12 at 13:37
  • I saw that question too. iFolder works using Apache apparently - I can't install/configure that on a NAS.
    – Joseph
    Jun 23 '12 at 15:45
  • There is more than one answer provided there. But I see what you're saying, and the NAS requirement probably does warrant it being different enough. The problem is, it may be completely dependant on the NAS' capabilities then. Perhaps also provide your NAS model, specifications, etc. Jun 23 '12 at 15:57
  • It shouldn't really matter. The Syncing should be done with a network folder. No matter what software is being run on the NAS. The other reason why the other answers were not satisfactory is that they were no easy solutions for macs. I am slowly beginning to believe, that Dropbox is really the only way. I am just surprised, that no one has made a similar software for local scenarios.
    – Joseph
    Jun 23 '12 at 20:05

10 Answers 10


Look at http://owncloud.org - it's basically a open source dropbox solution.

Don't know what NAS you have but most NAS boxes run on linux and you should be able to get some directions at the owncloud forums.

Otherwise i think Unison or rsync would be the best non server solutions in your case.

This links to a blog post describing the very same problem(and an acceptable solution) but for ubuntu. http://www.cerebralmastication.com/2011/04/fast-two-way-sync-in-ubuntu/

  • Why the downvote?
    – OakNinja
    Mar 13 '13 at 22:44

I looked at this some time ago too.

First, I have tried Sparkleshare which is nice for small document-like repo, but has all not-fun features of git (whole history) and not handle big files well.

I end up with Unison which is very nice software, have bi-directional sync of directories (with backups if there are merge conflicts) - works perfectly for large data. Go for it.


Recently I found really good tool: syncthing (recently they changed name to pulse). Has client for most of the platforms and it's pretty flexible in configuration with nice web-gui.

There is also git-annex, I was using it for short time but I stopped as it's required xmpp account to pass messages (recently this was removed so it's not required anymore but I'm staying with syncthing now for a while).



This little utility is really amazing. I've relied upon it since 2006.

Extremely fine-grained resolution, and nice scriptability if you need some conditionality given by external applications.

Sync manager runs silently in the background with and elaborate calendar.


If your using a Synology or Netgear NAS, the they both have an optional rsync daemon bundled, that you could enable, alternatively you could install a Unison daemon on the NAS, and the client on your Mac(s), see:




If you're using a Synology NAS, Cloud Station is the answer you're looking for. From the website:

"If you own multiple devices, Cloud Station is perfect for you to have files synced automatically to all of them. Your work will always be up to date among Mac, PC, and mobile devices. What’s more, you can now sync files with maximum size of 5GB. Files are always accessible via the web and the Cloud Station folders on your local computers. When your PC and DiskStation are in the same local area network (LAN), you can definitely enjoy a speedier transfer rate than what’s offered over the Internet."


If you then do some port forwarding, you would also have a web interface to your files through File Station in a similar (but prettier) way to Dropbox.

I personally own a Synology DS212 and have found this feature to work great. If you're in the market for a NAS, I recommend buying the previous model from Amazon, not the latest Synology, if you're looking for a better price.


Git and SVN are other options, not too sure about tortoise and mac though subversion definitely can run on mac (and is available by default).

  • How about automatic syncing when a new file is added, or an existing file is updated or removed. Will a cronjob do the trick?
    – SPRBRN
    Mar 26 '13 at 11:43

This seems to be a common question that really doesn't have one solid product yet. I have started using two. One that I use for backups (which I know isn't what you are looking for but figured i'd throw out there) is Bvckup http://www.bvckup.com/ . Recently, I started using AeroFS https://aerofs.com/ which has the same "shareability" as dropbox, but has no web interface. I'm pretty sure AeroFS will suite you best in this situation.

Since AeroFS is still in beta, I think you may need to get an invite. I can always give you one if interested.


Sher.ly can do what you need. Full disclosure: I'm running this project. Idea behind is Dropbox/Bitcasa solution working from your own storage, any type. We want to be much smarter than Dropbox: you can sync all your devices (if you want), but you do not have to download (sync) ALL data being shared with you - this is basic difference: data is available, not stuffing your drives. NOT not bi-directional access as you've described.

Means your can easily "link" several computers (Mac's, PC's, Linux underway) with small SSD storage with entire NAS with several TB of data. We will support storage servers (MS, Linux), and small appliances like RaspberryPI.

You start by creating a group by inviting members, add files (local or remote storage) and group members can instantly access the data; small files can be synced right away, bigger will be intentional download. Let me know if this answers your questions. Blazej Marciniak, @blazej_os


If you don´t want to install software on your NAS you will have a lot of configuration work on all your devices. But that´s your decision :).

You could use on a mac for example Forklift and create a synclet for an easier access (like in the dock) or you use Hazel and create a task for automation.


For your informations: It is possible to create a bi-directional sync with rsync - but it´s a little bit tricky. You have to create two rsync lines (one with option --update and with --delete).

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