How to share data across multiple machines

[Jonathan Kamens]

On 01/31/2014 08:38 AM, Yawar Amin wrote:
> On 2014-01-31, at 6:43, Jonathan Kamens <jik at kamens.us> wrote:
>> Why won't there be a lock when Dropbox is used? As far as I can tell, the lock is just a file that GnuCash creates in the filesystem in the same directory as the data file when it starts up, so when it creates that file, shouldn't Dropbox automatically sync it to the other machine(s)?
> If Dropbox replicates a lock file on a second machine, won't the GnuCash  instance running on the second machine think that the lock belongs to _it_?
Not exactly. Here is my understanding of how things work (happy to be 
corrected if I've got it wrong!)...

If you start GnuCash and it sees that the lock file already exists, you 
are offered four choices: Open Read-Only, Create New File, Open Anyway, 
and Quit. We can ignore Create New File and Quit since they don't help 
us run GnuCash in two places at the same time. ;-) That leaves Open 
Read-Only and Open Anyway.

Let's say that you do Open Read-Only, which means that you now have two 
different GnuCash instances running, which we'll call RW and RO. In RW, 
you will be able to continue to modify your data, but in RO, you can 
only view it. If you want to see changes in RO that were made in RW, you 
need to do File | Revert.

If, on the other hand, you do Open Anyway, then you'll now be able to 
modify your data in /both/ GnuCash instances. I suppose that 
theoretically, if you always, absolutely, positively remember to save 
changes in one instance, wait for it to sync (if you're using Dropbox), 
and then do File | Revert in the other instance before making changes 
there, this would work. But frankly it sounds really, incredibly 
dangerous and I wouldn't recommend it.

I'm not certain, but I don't think GnuCash has any sort of conflict 
detection, i.e., if you have two instances running, make changes in 
both, and then save the changes in both, I don't think the second 
instance will complain that you've just overwritten changes you made in 
another instance.

In short, you're safe as long as you pay attention to the lock files and 
don't try to open your data read-write in multiple places at the same time.

   jik