[ealexhudson]

The 'FROM scratch' with a single binary pattern is something I use a lot with stowage.org : basically, I can create series of containers that allow other developers to easily install and update dev-environment / build tool chain without having to do a bunch of packaging.

That said, I definitely agree that you don't want to do 'FROM scratch' unless you're definitely not re-using the various upper layers. Having a fat base image is a one-time cost that potentially pays itself back many times over.

[rtpg]

If you're running multiple containers of images that are themselves derived from a same image, is it still a one-time cost? Is Docker smart enough to run "only one" instance of Ubuntu, for example?

[stormbrew]

What resources are you concerned about being consumed?

- There will only ever be one running kernel with docker.

- The base filesystem layer, if identically hashed, will be shared as an overlay filesystem.

- The memory footprint of whatever each container runs (which will generally not be a full from runlevel0 system) will not be shared, except in the sense that binaries loaded into ram from the same overlay filesystem will have some of their disk pages shared.

[kosinus]

In practice, the base layers update often, and not all apps will be running from the same version.

[stormbrew]

That's true, but it is something that is potentially within your control as well.

[ealexhudson]

What stormbrew said above. It's probably not an absolutely O(1) cost but in practice I haven't noticed the difference. I definitely have noticed a saving from pushing many different "slim" alpine images around (alpine is not at fault here, but the more differences your images have, the less you get to re-use existing layers).