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Re: Dockerfile in OpenShift



Hi Den,



On Fri, Jan 22, 2016 at 9:32 AM, Den Cowboy <dencowboy hotmail com> wrote:
Thanks for the answers. I have 2 containers which need to work together: they are started by:

docker run -d --name "name1" test/image1:1

docker run -d -p 80:80 --name "name2" --link name1:name1 test/image2:1


The images are created with Jenkins and Docker. They're pushed to a private repository. I've pulled the images from the private repo so now the images are on my OpenShift-server.

So the first question is how do I have to perform the docker 'link' command in OpenShift.




Reading the docs in https://docs.docker.com/engine/reference/run/, seems that all the '--link' does is allow you to talk to another container by name when they're in the same bridge network.

In OpenShift, you may map that setup to having a Pod with multiple containers, or you might want to have one DeploymentConfig and one Service per image, and you can reference services in the same namespace by name.

In the first situation, you have the guarantee that the containers will be scheduled on the same node.
The advantage of the second scheme is that you can easily scale your deployments, and each independently.

It boils down to the relationship between your two images.

If they are something like "mysql" + "phpMyAdmin", then the first option my suit you well.
If you have two microservices that need to talk to each other, I'd recommend the second approach.




 


The second question is that I can't start a container from the image (I'm on OpenShift Origin 1.1 on Centos7)

oc new-app ec2-xxx:5000/test/image1:1


specify --allow-missing-images to use this image name.

The 'new-app' command will match arguments to the following types:

  1. Images tagged into image streams in the current project or the 'openshift' project
     - if you don't specify a tag, we'll add ':latest'
  2. Images in the Docker Hub, on remote registries, or on the local Docker engine
  3. Templates in the current project or the 'openshift' project
  4. Git repository URLs or local paths that point to Git repositories

A manual pull from the image of the registry is possible. I'm using selfsigned certificates:





Since you're pulling the image manually, in this case you can safely run:

 oc new-app ec2-xxx:5000/test/image1:1 --allow-missing-images


new-app doesn't inspect your local Docker images. That's because you might be running the oc client in a machine that has a Docker daemon and the given image, but that has no implication with the image existing in the OpenShift nodes where the image will be run.
Specifying  --allow-missing-images confirms that you will be responsible for ensure the image is available in the nodes, since it cannot be pulled from the internal registry nor DockerHub.
You might want to look into importing your images to your internal registry as ImageStreams:




--
Rodolfo Carvalho

OpenShift Developer Experience

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