Pulling images from private repository in kubernetes without using imagePullSecrets

As long as you're using Docker on your Kubernetes nodes (please note that Docker support has itself recently been deprecated in Kubernetes), you can authenticate the Docker engine on your nodes itself against your private registry.

Essentially, this boils down to running docker login on your machine and then copying the resulting credentials JSON file directly onto your nodes. This, of course, only works if you have direct control over your node configuration.

See the documentation for more information:

If you run Docker on your nodes, you can configure the Docker container runtime to authenticate to a private container registry.

This approach is suitable if you can control node configuration.

Docker stores keys for private registries in the $HOME/.dockercfg or $HOME/.docker/config.json file. If you put the same file in the search paths list below, kubelet uses it as the credential provider when pulling images.

• {--root-dir:-/var/lib/kubelet}/config.json
• {cwd of kubelet}/config.json
• ${HOME}/.docker/config.json
• /.docker/config.json
• {--root-dir:-/var/lib/kubelet}/.dockercfg
• {cwd of kubelet}/.dockercfg
• ${HOME}/.dockercfg
• /.dockercfg

Note: You may have to set HOME=/root explicitly in the environment of the kubelet process.

Here are the recommended steps to configuring your nodes to use a private registry. In this example, run these on your desktop/laptop:

• Run docker login [server] for each set of credentials you want to use. This updates $HOME/.docker/config.json on your PC.
• View $HOME/.docker/config.json in an editor to ensure it contains just the credentials you want to use.
• Get a list of your nodes; for example:
  • if you want the names: nodes=$( kubectl get nodes -o jsonpath='{range.items[*].metadata}{.name} {end}' )
  • if you want to get the IP addresses: nodes=$( kubectl get nodes -o jsonpath='{range .items[*].status.addresses[?(@.type=="ExternalIP")]}{.address} {end}' )
• Copy your local .docker/config.json to one of the search paths list above.for example, to test this out: for n in $nodes; do scp ~/.docker/config.json root@"$n":/var/lib/kubelet/config.json; done

Note: For production clusters, use a configuration management tool so that you can apply this setting to all the nodes where you need it.

If the Kubernetes cluster is private, you can deploy your own, private (and free) JFrog Container Registry using its Helm Chart in the same cluster.

Once it's running, you should allow anonymous access to the registry to avoid the need for a login in order to pull images.

If you prevent external access, you can still access the internal k8s service created and use it as your "private registry".

Read through the documentation and see the various options.

Another benefit is that JCR (JFrog Container Registry) is also a Helm repository and a generic file repository, so it can be used for more than just Docker images.