Docker – Using a Newer Client with an Older Host

docker

We have a slightly older Docker server running on RHEL 6.6. It's not well-supported by our operations team right now, so we can't upgrade easily. Right now it runs Docker 1.3.2 from an EPEL repo. If I ssh in it does everything that I need for proofs-of-concept that will hopefully help me push management to improve the infrastructure support for Docker down the road.

I set it up to listen on TCP/TLS, and I'm able to connect to it, but it refuses to run commands given by my local docker client.

$ docker version
Client version: 1.4.1
Client API version: 1.16
Go version (client): go1.4
Git commit (client): 5bc2ff8
OS/Arch (client): darwin/amd64
FATA[0000] Error response from daemon: client and server don't have same version (client : 1.16, server: 1.15)

I know the connection itself works because fig works:

$ cat > fig.yml
test:
    image: busybox
$ fig run --rm test sh
/ # hostname -f
084f75fb59d4

Is there some way I can tell the newer docker client to use the older docker API version until I can access to a newer docker host?

Best Answer

Since Docker 1.10.0, there's an option for overriding the API Version used for Docker client communication with Docker engine.

Just by using the DOCKER_API_VERSION environment variable.

Ex.:

$ docker version
Client:
 Version:      1.10.0
 API version:  1.22
 Go version:   go1.5.3
 Git commit:   590d510
 Built:        Fri Feb  5 08:21:41 UTC 2016
 OS/Arch:      darwin/amd64
Error response from daemon: client is newer than server (client API version: 1.22, server API version: 1.21)

$ DOCKER_API_VERSION=1.21 docker version
Client:
 Version:      1.10.0
 API version:  1.21
 Go version:   go1.5.3
 Git commit:   590d510
 Built:        Fri Feb  5 08:21:41 UTC 2016
 OS/Arch:      darwin/amd64

Server:
 Version:      1.9.1
 API version:  1.21
 Go version:   go1.4.3
 Git commit:   a34a1d5
 Built:        Fri Nov 20 17:56:04 UTC 2015
 OS/Arch:      linux/amd64

Reference: https://docs.docker.com/engine/reference/commandline/cli/#environment-variables

EDIT

Since Docker 1.13, CLI has an improved backwards compatibility. According to https://blog.docker.com/2017/01/whats-new-in-docker-1-13 :

Starting with 1.13, newer CLIs can talk to older daemons. We’re also adding feature negotiation so that proper errors are returned if a new client is attempting to use features not supported in an older daemon. This greatly improves interoperability and makes it much simpler to manage Docker installs with different versions from the same machine.

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