Kubernetes Walkthrough

October 16, 2018 ยท View on GitHub

Once your Kubernetes cluster has been created you will have a resource group containing:

  1. One master accessible by SSH on port 22 or kubectl on port 443
  2. A set of nodes in an availability set. The nodes can be accessed through a master. See agent forwarding for an example of how to do this.

The following image shows the architecture of a container service cluster with 1 master, and 2 agents:

Image of Kubernetes cluster on azure

In the image above, you can see the following parts:

  1. Master Components - The master runs the Kubernetes scheduler, api server, and controller manager. Port 443 is exposed for remote management with the kubectl cli.
  2. Nodes - the Kubernetes nodes run in an availability set. Azure load balancers are dynamically added to the cluster depending on exposed services.
  3. Common Components - All VMs run a kubelet, Docker, and a Proxy.
  4. Networking - All VMs are assigned an ip address in the 10.240.0.0/16 network. Each VM is assigned a /24 subnet for their pod CIDR enabling IP per pod. The proxy running on each VM implements the service network 10.0.0.0/16.

All VMs are in the same private VNET and are fully accessible to each other.

Create your First Kubernetes Service

After completing this walkthrough you will know how to:

  • Access Kubernetes cluster via SSH,
  • Deploy a simple Docker application and expose to the world,
  • The location of the Kube config file and how to access the Kubernetes cluster remotely,
  • Use kubectl exec to run commands in a container,
  • And finally access the Kubernetes dashboard.

Follow these steps:

  1. After successfully deploying the template write down the master FQDNs (Fully Qualified Domain Name).
    • If using Powershell or CLI, the output parameter is in the OutputsString section named 'masterFQDN'
    • If using Portal, to get the output you need to:
      1. Navigate to "resource group"
      2. Click on the resource group you just created
      3. Then click on "Succeeded" under last deployment
      4. Then click on the "Microsoft.Template"
      5. Now you can copy the output FQDNs and sample SSH commands Image of docker scaling
  2. SSH to the master FQDN obtained in step 1.
  3. Explore your nodes and running pods:
    • To see a list of your nodes type kubectl get nodes. If you want full detail of the nodes, add -o yaml to become kubectl get nodes -o yaml.
    • To see a list of running pods type kubectl get pods --all-namespaces.
  4. Start your first Docker image by typing kubectl run nginx --image nginx. This will start the nginx Docker container in a pod on one of the nodes.
  5. Type kubectl get pods -o yaml to see the full details of the nginx deployment. You can see the host IP and the podIP. The pod IP is assigned from the pod CIDR on the host. Run curl to the pod ip to see the nginx output, eg. curl 10.244.1.4 Image of curl to podIP
  6. The next step is to expose the nginx deployment as a Kubernetes service on the private service network 10.0.0.0/16:
    1. Expose the service with command kubectl expose deployment nginx --port=80.
    2. Get the service IP kubectl get service
    3. Run curl to the IP, eg. curl 10.0.105.199 Image of curl to service IP
  7. The final step is to expose the service to the world. This is done by changing the service type from ClusterIP to LoadBalancer:
    1. Edit the service: kubectl edit svc/nginx
    2. Change type from ClusterIP to LoadBalancer and save it. This will now cause Kubernetes to create an Azure Load Balancer with a public IP.
    3. The change will take about 2-3 minutes. To watch the service change from "pending" to an external ip, type watch 'kubectl get svc' Image of watching the transition from pending to external ip
    4. Once you see the external IP, you can browse to it in your browser: Image of browsing to nginx
  8. The next step in this walkthrough is to show you how to remotely manage your Kubernetes cluster. First download Kubectl to your machine and put it in your path:
  9. The Kubernetes master contains the kube config file for remote access under the home directory ~/.kube/config. Download this file to your machine, set the KUBECONFIG environment variable, and run kubectl to verify you can connect to cluster:
    • Windows to use pscp from putty. Ensure you have your certificate exposed through pageant: 
      # MASTERFQDN is obtained in step1
pscp -P 22 azureuser@MASTERFQDN:.kube/config .
SET KUBECONFIG=%CD%\config
kubectl get nodes
    • OS X or Linux: 
      # MASTERFQDN is obtained in step1
scp azureuser@MASTERFQDN:.kube/config .
export KUBECONFIG=`pwd`/config
kubectl get nodes
  10. The next step is to show you how to remotely run commands in a remote Docker container:
    1. Run kubectl get pods to show the name of your nginx pod
    2. Using your pod name, you can run a remote command on your pod. eg. kubectl exec nginx-701339712-retbj date
    3. Try running a remote bash session. eg. kubectl exec nginx-701339712-retbj -it bash. The following screen shot shows these commands: Image of curl to podIP
  11. The final step of this tutorial is to show you the dashboard:
    1. Run kubectl proxy to directly connect to the proxy
    2. In your browser browse to the dashboard
    3. Browse around and explore your pods and services. Image of Kubernetes dashboard