Using Openshift Container Platform ‘s2i’ with a TCP Docker daemon

I am using a Docker TCP socket to connect to a remote docker daemon. I run Docker on a remote host so that I can access my containers from both of my development machines. Of course the Docker TCP socket should be secured with TLS authentication in order to protect it from malicious use. You can read how to do that here.
Sometimes I want to make use of Docker images which we ship in the Red Hat Docker registry, but they are designed to be used in Openshift. They are not designed to be used ‘standalone’, but to be used with the ‘s2i’ tool, which is part of the Openshift Container Platform.
If you’ve tried to use ‘s2i’ with a Docker TCP socket, you might have found that you get this error message, “Unable to connect to Docker daemon. Please set the DOCKER_HOST or make sure the Docker socket “tcp://” exists“, and the ‘s2i’ manual pages hard to decipher. I had to dig into the source code to figure out the correct configuration to use. You need to set the following Environment variables:
export DOCKER_HOST=tcp://
export DOCKER_CERT_PATH=~/.docker/

Once you set those, you should be able to use ‘s2i’ to develop containerized apps locally using images from the Red Hat Docker Registry.

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