Before you start to run your first container in Kubernetes, it's better to check if your cluster is in a healthy mode. A checklist showing the following items would make your kubectl sub commands stable and successful, without unknown errors caused by background services:
- Checking the master daemons. Check whether the Kubernetes components are running:
// get the components status
$ kubectl get cs
NAME STATUS MESSAGE ERROR
controller-manager Healthy ok
scheduler Healthy ok
etcd-0 Healthy {"health": "true"}
- Check the status of the Kubernetes master:
// check if the master is running
$ kubectl cluster-info
Kubernetes master is running at https://192.168.122.101:6443
KubeDNS is running at https://192.168.122.101:6443/api/v1/namespaces/kube-system/services/kube-dns/proxy
To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
- Check whether all the nodes are ready:
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
ubuntu01 Ready master 20m v1.10.2
ubuntu02 Ready <none> 2m v1.10.2
Ideal results should look like the preceding outputs. You can successfully fire the kubectl command and get the response without errors. If any one of the checked items failed to meet the expectation, check out the settings in the previous recipes based on the management tool you used.
- Check the access permission of the Docker registry, as we will use the official free image as an example. If you want to run your own application, be sure to dockerize it first! What you need to do for your custom application is to write a Dockerfile (https://docs.docker.com/engine/reference/builder/), and build and push it into the public or private Docker registry.
Test your node connectivity with the public/private Docker registry
On your node, try the Docker pull nginx command to test whether you can pull the image from the Docker Hub. If you're behind a proxy, please add HTTP_PROXY into your Docker configuration file(https://docs.docker.com/engine/admin/systemd/#httphttps-proxy). If you want to run the image from the private repository in the Docker Hub, or the image from the private Docker registry, a Kubernetes secret is required. Please check Working with secrets, in Chapter 2, Working through Kubernetes Concepts, for the instructions.