Dropbox created a duplicate of all files, with "._" in front of each file name

Question

I'm having a problem with dropbox. I've recently added a user to 2 of my dropbox folders (for group works), and from then all files uploaded by anybody in those folders are "duplicated" (just once) with a file of the same type (.pdf, .jpg, ...) all of the same size of 4 kb (no matter the dimension of the original files), and with the same name with "._" in front of each name. None of the duplicates are openable by their corresponding software.

I've never had this problem before, and none of the other participants in those folders had it either (before now), apart from the one I've mentioned above. Also, none of my other folders in dropbox have this problem, so I've deduced that he is the origin of the problem.

Now, he uses a Macbook, while the rest of us use windows OS (on Asus, Hp, ...), but I've already added mac users before in other folders without this problem, which is very annoying (especially in subfolders with dozens of files, and considering that also the subfolders themselves have a corresponding duplicate).

One more thing, they are deletable, but soon they come back just where they were. (Maybe a case of 'the cat came back'? ^^' Sorry, couldn't resist)

I didn't find anything about it on google, just mentions about multiple duplicates, but this is not the same, I think.

Please help me, I don't know what to do about it.

Answer 1

The ._ files are generated by the Macbook user's OS - used to store additional meta information about that file. Dropbox is not really creating them, they are simply being copied from the Macbook user's machine. These files are normally "hidden" and hopefully the "hidden" attribute is still intact so they can probably be hidden on the Windows machines as well.

More information:
Is there any way to prevent a Mac from creating dot underscore files?

Answer 2

I found this post a few weeks back when I was looking for information about sharing a Dropbox folder between Windows and macOS using Bootcamp. Since then I've done a fair bit of investigation, which I've written up here: http://www.dylanbeattie.net/2017/01/sharing-dropbox-folder-using-bootcamp.html

Short answer: they're not created by Dropbox, they're created by macOS if you're using a non-standard filesystem, which I suspect your macOS-using collaborator is doing. They're normally hidden files so you'll never seen them, but Dropbox picks them up and syncs them to any other devices - and in some cases they lose the hidden attribute. Rather than deleting them, you can set them to hidden on a Windows machine using this command:

C:\Users\me\Dropbox> for /r %1 in (._*) do attrib +h "%1"

That's saying 'find every file in this folder and subfolders whose names matches the pattern ._* (i.e. dot-underscore followed by anything), and set the Hidden attribute on that file to true'

Answer 3

In my experience using Dropbox on 100% Macs which have finder set to show all dot files, I have only seen this occurring when using an external drive for my Dropbox.