I don't use the firefox version but the standalone app which runs great on my linux box and my Mac.
I have a bunch of Dropbox space and the fact that Zotero doesn't play super nice with +Dropbox was a bit of a pain (you just had to point Mendeley at your +Dropbox folder and you were done). For a while I've just been using Zotero's base online storage but today I've just set it up to work on Dropbox so I thought I'd record how I've done it.
I asked a while back about this on +Google+ and had a bunch of people telling me: oh just use symbolic links it's super easy. Symbolic links have been one of those things I've been meaning to understand for a while but at that moment in time I just nodded and smiled. This morning I've just taken the time to figure it out and in particular see how to set it up to work with Zotero. It is super easy and so I thought I'd write a post in case it helps anyone and also to make sure I remember how to do it. I also didn't seem to be able to find anywhere online that explains the second half of what you need to do so that's here too.
First of all, if you check forums and stuff, there's a big safety warning with using Dropbox with Zotero. I understand that this is mainly because Zotero has multiple things going on: a database (that knows what is what and who wrote what etc) but also a storage folder (which contains the pdfs). This post is about division of labour: we're going to setup Zotero to take care of the database and +Dropbox to take care of the pdfs. There are basically 2 steps on 1 computer and 2 on every other.
If you use the preferences and change the data directory to dropbox, then if you're running on more than one box you will most likely corrupt the database (which is a bad thing: 'run you fools!').
So basically: don't mess with your data directory.
The 'solution' (I think) is to use 'symbolic links' to trick your computer in to thinking that your storage folder is also on your +Dropbox ( +Dropbox are the 'idiots' here and won't know the difference and just sync it all).
So to do that, choose computer 1. On computer 1 you setup a symbolic link from your Zotero storage file to your +Dropbox folder. This is what I did:
Step A1. Go to your preferences in Zotero and click on 'Show Data Directory'. This will open up your zotero folder (which contains the storage folder that we're looking for). Remember the path for this (click on info, or properties or something).
Step A2. Now for the magic trick: we create a symbolic link:
ln -s paththatitoldyoutoremember/storage ~/Dropbox/Literature/ZoteroStorage/
This tells computer 1 (and +Dropbox) that there's a folder in /Dropbox/Literature/ that contains folders with all your pdfs (it actually contains directories for each file):
That is however not everything. You now need to go to your other machines and tell Zotero on there that the storage file isn't exacly what it thinks it is (we trick it).
Step B1. So on computer 2 (and any other computer) go to the Zotero folder (remember just click on 'Show Data Directory' to find the path which you want to remember ie copy to your clipboard) and delete the storage folder (I think: be careful, don't sue me...):
rm -r otherpaththatitoldyoutoremember/storage
(make sure it deletes, when I did this on one machine I had to get rid of the folder again for some reason)
Step B2. Once we've done that we need to tell zotero not to worry and create a symbolic link of the storage folder (which it thinks is an actual folder) that is now in our +Dropbox:
ln -s ~/Dropbox/Literature/ZoteroStorage/ otherpaththatitoldyoutoremember/storage
That's basically it. If you now take a look at that folder/symlink on computer 2 you'll see all the folders (containing the pdfs) from your other machine (I'm blurring a bit of the path in case that somehow tells you my credit card number):
+Dropbox will first of all copy over the pdfs to all the right places (the symbolic links take care of the pdfs) and then when you sync zotero it'll also have the correct data (Zotero takes care of the database).
(Finally you can go to your preferences on Zotero on all your machines and turn off attachment syncing as +Dropbox is now taking care of that).