how does rclone union work?

Hi, I'd like to know (more deeply then rclone wiki) how rclone union works.

  • Are uploaded files spread throughout all drives in the union or every drive is filled sequentially?

  • If I have 20 free google drive account can I use them as one 300GB encrypted drive without problems of uploading/limits etc?

  • If a file doesn't fill a drive (or remaining space in a drive), is it divided into several drives?

The union backend got a significant upgrade in the latest beta so I suggest you check its docs out at That has well defined policies so you can work out exactly what happens.

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hey @ncw, thanks for the reply.
I do share @fazi's doubts about the rclone union command...
still, I haven't found the provided link to be informative, at all. oO
could you please elaborate a bit more? thanks!

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What information are you missing that's not there?

well, I got here through a web search to understand how rclone union works.
I don't know anything about unionFS or mergerFS, but I was kind of expecting to be able to answer exactly the questions that the OP asked a couple of months ago.
still, after having read the links, which seems to me to be the future stable documentation, all my doubts are still there.
what does union do?
I feel like the documentation gives a lot for granted. :slight_smile:
thanks for the help!

Union allows you to combine multiple drives/remotes into a single mount point.

It really comes down to explaining what problem you are trying to solve and what can be used to solve said problem.

The OP's questions are answered from my reading in the documentation based on the policy information that is in there, which is why the OP probably didn't follow up.

The policies are fairly low level and complex as is unfortunately the gritty nature of union and how it works as it's something done at a low level.

If you have a specific question on it, please ask.

I have discovered rclone only recently, and I am just starting to understand its capabilities and limits.

let's just say I have four accounts: Box, Dropbox, MEGA, Google Drive.
I can define a rclone union of the four remotes.
can I then copy a file over using rclone copy? where does the file go?
similarly, if each remote holds 1 GB, can I say my union remote holds 4 GB?

I understand some things are low level, but I believe we are missing a simple higher level explanation for the feature!

furthermore, I can see from the documentation that, for example, rclone about does not work with Box quotas, and that rclone check does not work with MEGA hashes.
then what happens to the union remote? I'm confused.


let's think of the simplest use case I can imagine: merging all of my cloud storage options together for a single unified backup remote.

I don't care where files go, as long as they're backed up.
hopefully, rclone will avoid hitting hard disk quotas on each service.

if I create the rclone union, what should I do before starting to use it, e.g. rclone sync ~/Docs backupRemote:Docs ?
do I need to set up or config anything?
is there a default policy?

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