Skip to content

Latest commit

 

History

History
170 lines (106 loc) · 4.76 KB

basic-deployment.md

File metadata and controls

170 lines (106 loc) · 4.76 KB
Raw

Basic Deployment

In this exercise, you will deploy an nginx web server to a Kubernetes Cluster, and access the default nginx welcome page in your browser.

It is not expected that you understand everything going on, yet.

Learning Goals

  • Use the Kubernetes command line interface (CLI) kubectl.
  • Run and access an application in Kubernetes.

Introduction

In Kubernetes, we run containers, but we don't manage containers directly. Containers are instead placed inside pods. A pod contains containers.

Pods in turn are managed by controllers, the most common one is called a deployment.

In this exercise, you will create a deployment, which will create a pod, in which your container will be running.

Interacting with Kubernetes using kubectl

We will be interacting with Kubernetes using the command line.

The Kubernetes CLI is called kubectl, and allows us to manage our applications and Kubernetes itself.

To use it, type kubectl <subcommand> <options> in a terminal.

Exercise

Overview

  • Run an application in a pod using the kubectl create command
  • Make the application accessible from the Internet

Step by step instructions

Step by step:

Run application using kubectl create command

We will use the nginx webserver as an example of an application you might want to run in Kubernetes.

Here is the command to do it:

kubectl create deployment nginx --image=nginx:latest

Expected output:

deployment.apps/nginx created

We can ask Kubernetes about what resources it has, such as our pod.

We do this using the kubectl get <kind> command, in this case the <kind> will be pod(s).

Verify that your pod was created and is running using kubectl:

kubectl get pods

Expected output:

NAME                     READY   STATUS    RESTARTS   AGE
nginx-6d666844f6-tjvk5   1/1     Running   0          15s

Awesome! Nginx is running.

Make the application accessible from the internet

We are getting a little ahead of our exercises here, but to illustrate that we actually have a functioning webserver running in our pod, let's try exposing it to the internet and access it from a browser!

First use the following command to create a service for your deployment:

💡 A service is a networking abstraction that enables a lot of the neat networking features of Kubernetes. We will cover services in detail in a later exercise, so just go with it for now :-)

kubectl expose deployment nginx --port 80 --type NodePort

Expected output:

service/nginx exposed

Get the service called nginx and note down the NodePort, by finding the PORT(S) column and noting the number on the right side of the colon :

kubectl get service nginx

Expected output:

NAME        TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
nginx       NodePort   10.96.223.218   <none>        80:32458/TCP   12s

In this example, Kubernetes has chosen port 32458, you will most likely get a different number.

Finally, look up the IP address of a node in the cluster with:

kubectl get nodes -o wide

💡 The -o wide flag makes the output more verbose, i.e. to include the IPs

Expected output:

NAME    STATUS   . . . INTERNAL-IP  EXTERNAL-IP     . . .
node1   Ready    . . . 10.123.0.8   35.240.20.246   . . .
node2   Ready    . . . 10.123.0.7   35.205.245.42   . . .

In the example your external IPs are either 35.240.20.246 or 35.205.245.42.

Since your service is of type NodePort it will be exposed on all of the nodes. The service will be exposed on the port with the number you noted down above.

Choose one of the EXTERNAL-IP's, and point your web browser to the address: <EXTERNAL-IP>:<PORT>.

In this example, the address could be 35.240.20.246:32458, or 35.205.245.42:32458.

You should see the default nginx webpage in your browser.

More details

This section has some optional extra details.

More details about pods

A pod (not container) is the smallest building-block/worker-unit in Kubernetes, it has a specification of one or more containers and exists for the duration of the containers; if all the containers stop or terminate, the Pod is stopped.

More details about deployments

Usually a pod will be part of a deployment; a more controlled or robust way of running pods. A deployment can be configured to automatically delete stopped or exited Pods and start new ones, as well as run a number of identical Pods e.g. to provide high-availability.

Clean up

Delete the resources you have created using kubectl delete <kind> <name>

kubectl delete deployment nginx
kubectl delete service nginx