I want to build some docker images in a certain step of my Google Cloud Build, then push them in another step. I'm thinking the CI used doesn't really matter here.
This is because some of the push commands are dependent on some other conditions and I don't want to re-build the images.
I can docker save to some tar in the mounted workspace, then docker load it later. However that's fairly slow. Is there any better strategy? I thought of trying to copy to/from /var/lib/docker, but that seems ill advised.
The key here is doing the docker push from the same host on which you have done the docker build.
The docker build, however, doesn’t need to take place on the CICD build machine itself, because you can point its local docker client to a remote docker host.
To point your docker client to a remote docker host you need to set three environment variables.
On a Linux environment:
This is a very powerful concept that has many uses. One can for example, point to a dev|tst|prod docker swarm manager node. Or, point from Linux to a remote Windows machine and initiate the build of a Windows container. This latter use case might be useful if you have common CICD tooling that implements some proprietary image labeling that you want to re-use also for Windows containers.
The authentication here is mutual SSL/TLS and so there need to be both client and server private/public keys generated with a common CA. This might be a little tricky at first and so you may want to see how it works using docker-machine first using the environment setting shortcuts initially: https://docs.docker.com/machine/reference/env/
Once you’ve mastered this concept you’ll then need to script the setting of these environment variables in your CICD scripts making client certs available in a secure way.