Images

Each container in a pod has its own image. Currently, the only type of image supported is a Docker Image.

You create your Docker image and push it to a registry before referring to it in a kubernetes pod.

The image property of a container supports the same syntax as the docker command does, including private registries and tags.

Using a Private Registry

Keys for private registries are stored in a .dockercfg file. Create a config file by running docker login <registry>.<domain> and then copying the resulting .dockercfg file to the kubelet working dir. The kubelet working dir varies by cloud provider. It is / on GCE and /home/core on CoreOS. You can determine the working dir by running this command: sudo ls -ld /proc/$(pidof kubelet)/cwd on a kNode.

All users of the cluster will have access to any private registry in the .dockercfg.

Preloading Images

Be default, the kubelet will try to pull each image from the specified registry. However, if the imagePullPolicy property of the container is set to PullIfNotPresent or PullNever, then a local image is used (preferentially or exclusively, respectively).

This can be used to preload certain images for speed or as an alternative to authenticating to a private registry.

Pull Policy is per-container, but any user of the cluster will have access to all local images.