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April 23, 2012

Sync folders between multiple computers with Dropbox

In the world of “cloud” sync, backup and sharing, Dropbox is a rampaging success story. Whether you’re a fan or not, it has a huge worldwide take up of people who want to sync files between their computers, including their ipad, and keep an automatic backup of their files.

There’s loads on the web about dropbox so in this post I’m going to concentrate on something called symbolic links and syncing shared folders this way.

Briefly…what is it and what can it do?

If you connect one computer to dropbox it will take a copy of any files you put into your “dropbox” (a special folder on your computer) and store these duplicate files on their cloud servers. Whenever you change or delete a file on your computer, it will change or delete the file on the dropbox server too. This gives you an automatic backup of your files. If your computer is ever the victim of a cup of spilt coffee, you still have your precious files backed up online.

As good as that is, there are similar services that do this and probably better. Dropbox comes into its own when you add another computer, or share these folders with a friend or colleague. If you choose to share one of your folders with another computer, like your PC laptop or your friend’s iMAC, it will put the duplicate file on their computer too. If they change or delete the file, it will change or delete it on both the dropbox server and on your computer. This way the files are kept in sync. Revisions are held on the dropbox server so you can restore deleted files if needed.

One of the best things about Dropbox is it has a free 2GB account so you can try it out and see if it works for you before paying a cent. This is probably enough memory for a lot of people or even businesses who want to share and/or backup a limited number of files.

It also has a native iPad app so you can have the latest copy of your files in your hot little hand. It will only show you files an iPad can view: photos, office docs, pdfs and text files etc. You have control of how much is locally stored so you don’t need to worry about overloading an iPad.

OK enough about that.

Symbolic Links

A big limitation is that dropbox will only allow you to sync files that are in your “dropbox” folder. So you can’t directly sync files in your current folders. Or can you? Yes, actually you can, but it isn’t a feature of dropbox. Using “symbolic links” on either a windows or mac machine you can create a virtual link between your dropbox folder and any folder on your computer. For mac get a free little program called Mac Drop Any and for PC try Dropbox Folder Sync. Both work great.

linking shared folders using sym links

You will run into dramas when trying to do this with a shared folder on your collegue’s computer. I mean, if you want to share a folder using a sym link as above and your colleague on another computer wants this shared folder to be a sym link to a folder in their existing folder structure. If they create a folder with the same name and then try to make it a sym link to dropbox, it will create a new folder with a number, like “my folder (1)” in dropbox. Not what you want.

That’s because that folder already exists. Even worse, if your friend pulls this existing folder out of their dropbox, and creates a symlink between their new folder and dropbox, you will find all your files in that folder just got deleted! As far as dropbox is concerned your friend has just delete all the files that were there.

This is the procedure that works…

  1. Sync the shared folder to your friend’s computer.
  2. They quit the dropbox application to stop file syncing.
  3. They move this shared file into their directory structure, wherever they want it.
  4. Now they create a sym link using one of the programs above (or the command line).
  5. They turn dropbox back on. It will sync everything in their folder to you, but it is smart enough to recognise if files haven’t changed so it should be quick.

You’re done! Both should now have sym links to the same shared folder in dropbox. e.g. a PC could have a folder “shared stuff” in My Documents that is synced with a folder of the same name in the Documents of a friend’s Mac (or PC).

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