[seiferteric]

Somewhat unrelated. Is there a way to ship a container image with just a "diff" of the default image. Say I build a container with ubuntu 14.04 + some packages installed with apt. I would like to be able to "export" the filesystem, but only the files that are not present in the base os image. The reason I would like this is that I would like to use docker (or systemd-nspawn) to run containers on an device that will not always have access to the internet. It would be nice to be able to add a new package to that device, and not be multi 100 MBs. As long as I can guarantee that the base image is present on the device, I should not need to include it in the image.

[TheDong]

You can hack this up yourself using the output from 'docker save'. 'save' produces a tarball which contains layers, and you can delete the layers from your 'save' tarball that you know you already have on the destination.

[cpitman]

As long as you are pulling images from a docker registry, this should automatically happen.

[seiferteric]

Ya the point is it won't have access to a registry. I would like to be able to ship docker "packages" that have everything they need, but not have a lot of duplicate data (the base os image) in each package. I should be able to have the base image as its own package for example, and the other packages just have the "diff" files that they need.

[16bytes]

Last I checked. Docker will pull a delta when resolving new containers, but will export the entire thing if you want something for offline usage.

I had the same question as OP and didn't find anything that works as he described it when I looked 6+ months ago.