Docker version compatibility

General Discussions General
1

Docker images appear to be compatible (both forwards and backwards) across different versions of Docker.

By that I mean an image built with a new version of Docker runs OK under and old version and vice versa

How is this so ?
Is it expected to remain this way in future versions ?

2

I try to maintain always with the last version with docker-machine upgrade <vm-name>.

But there is VMs from other maintainers that is not possible to upgrade this way. In this case am using dvm (docker version manager) from http://getcarina.com.
If I want a new docker client version like 1.8.2 for example just install with:

$ dvm install 1.8.2
Installing 1.8.2...
Now using Docker 1.8.2

To change docker client version:

$ dvm use 1.8.2
Now using Docker 1.8.2

To check installed versions:

$ dvm ls
->  1.8.2
    1.8.3
    1.9.0
    system (1.9.0)
3

Hello Wellington, thank you for your reply.

What I’m asking about is the means that enable an image built using Docker version X to run on a machine running Docker version Y.

What makes them compatible ? Is this backwards compatibility likely to break in future ?

4

I note that the Docker registry does not identify which version of Docker was used to build an image, this suggests it has no relevance. Why is this ?