[Base] Terminology for docker/atomic images

[Dusty Mabe]

On Mon, Sep 08, 2014 at 09:28:20AM -0400, Adam Young wrote:
> On 09/07/2014 11:22 PM, Dusty Mabe wrote:
> >Hi All,
> >
> >Per discussion in the #fedora-cloud meeting last Friday I would like to
> >start a thread about the names of the Docker and Atomic deliverables for F21.
> >
> >I know of at least a few cases where there has been confusion regarding
> >what deliverable has been the subject of a conversation on IRC as a result
> >of the current terminology. I've seen the docker and atomic referred to as:
> >
> >     Docker Image
> >     Atomic Image
> >     Docker Host Image
> >     etc...
> >
> >It seems like the one that sparks the most confusion is "Docker Image".
> >Usually when I see "Image" I think a VM bootable image (i.e. virtualization,
> >not containers/Docker). A progression from that misunderstanding could lead
> >one to think that "Docker Image" is the VM disk image I can use to boot a
> >host that will run the Docker daemon and thus run containers.
> >
> >I think it would be nice to help ourselves and our users along by separating
> >the terminology a bit such that it is hard to confuse what is a VM disk
> >image vs. what is an image for use with Docker.
> >
> >Here is a first stab at trying to make things clearer:
> >
> >
> >     Docker Container Image - base container image - can be used with docker
> >     Atomic Image           - minimal OS, Atomic updates, aka 'Docker Host'
> I've always thought container and image were two distinct things.

Image and container are two distinct things. The container image is basically an
image that contains a filesystem for use with containers (no kernel, etc..).

A container is an isolated process that runs that uses the container image as
the root filesystem. 

> 
> 
> Here's my take:
> 
> 
> The image is the disk that is being used.  The container is the
> Operating System construct.  The  Two combinded are the instance.
> 
> "My instance is a Fedora 21 base image running inside a KVM container."
> 
> "My instance is a Docker image of JBoss with RHQ in it running in a
> container on CentOS 7"

I think you are mixing virtualization and containerization too much. Let me try
to see if I can use similar statements in my own terms:

"My virtual machine instance is a Fedora 21 base image running on a KVM hypervisor"

"My container is running process X that is using a docker container image of JBoss 
 with RHQ in it. The Docker daemon managing my container is running on a CentOS 7 host."

Hopefully my take on this isn't wrong. Does this help at all?

Dusty