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Kubernetes Hands-on Lab 2: Advanced Topics

Part 1: Multi-container pods

1. Create a deployment with a sidecar

Write a deployment as yaml with the following properties:

  • Name the deployment "sidecar-deployment"
  • The first container is called "main-container". It is a busybox (image=busybox) that writes "Hello from main-container" to a file every 3 seconds: while true; do echo "Hello from main-container" >> /mnt/log.txt;sleep 3; done;
  • The second container is called "sidecar-container". It is a busybox that reads the file and logs each line: tail -f /mnt/log.txt
  • Use an empty volume to write to and read from: https://kubernetes.io/docs/concepts/storage/volumes/#emptydir Deploy the yaml.
solution

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: sidecar-deployment
  name: sidecar-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: sidecar-deployment
  template:
    metadata:
      labels:
        app: sidecar-deployment
    spec:
      containers:
      - name: main-container
        image: busybox
        command: ['sh', '-c', 'while true; do echo "Hello from main-container" >> /mnt/log.txt;sleep 3; done;']
        volumeMounts:
        - name: logging-data
          mountPath: /mnt
      - name: sidecar-container
        image: busybox
        command: ['sh', '-c', 'tail -f /mnt/log.txt']
        volumeMounts:
        - name: logging-data
          mountPath: /mnt
      volumes:
      - name: logging-data
        emptyDir: {}
kubectl create -f sidecar-deployment.yaml

2. Read the logs from each container

Read the logs continuously using the follow flag. Use: https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#logs

If everything worked out, you should only see logs from the sidecar-container.

solution

kubectl logs deployment/sidecar-deployment -c main-container --follow
kubectl logs deployment/sidecar-deployment -c sidecar-container --follow

3. Create a pod with an initContainer.

  • Create a pod with an nginx container exposed on port 80.
  • Add a busybox initContainer which downloads a page using "wget -O /work-dir/index.html http://neverssl.com/online".
  • Make a volume of type emptyDir and mount it in both containers.
  • For the nginx container, mount it on "/usr/share/nginx/html" and for the initContainer, mount it on "/work-dir".
  • Do a port-forward to the pod (port 80 to port 80 on your machine) and open localhost:80 in a browser. You should see the downloaded website.
solution

apiVersion: v1
kind: Pod
metadata:
  name: init-container-pod
spec:
  initContainers:
  - image: busybox
    name: box
    command: ['sh', '-c', 'wget -O /work-dir/index.html http://neverssl.com/online']
    volumeMounts:
      - name: vol
        mountPath: /work-dir
  containers:
    - image: nginx
      name: nginx
      ports:
        - containerPort: 80
      volumeMounts:
        - name: vol
          mountPath: /usr/share/nginx/html
  volumes:
    - name: vol
      emptyDir: {}
kubectl port-forward pod/init-container-pod 8080:80

Part 2: Config Maps

https://kubernetes.io/docs/concepts/configuration/configmap/

1. Create a configmap named config with values foo=lala,foo2=lolo

solution

kubectl create configmap config --from-literal=foo=lala --from-literal=foo2=lolo

2. Display its values

solution

kubectl get cm config -o yaml
# or
kubectl describe cm config

3. Create and display a configmap from a file

Create the file with

echo -e "foo3=lili\nfoo4=lele" > config.txt
solution

kubectl create cm configmap2 --from-file=config.txt
kubectl get cm configmap2 -o yaml

4. Create a configMap called 'options' with the value var5=val5. Create a new nginx pod that loads the value from variable 'var5' in an env variable called 'option'

Hint: Read https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-configmap/#define-a-container-environment-variable-with-data-from-a-single-configmap

solution

kubectl create cm options --from-literal=var5=val5
kubectl run nginx --image=nginx --restart=Never --dry-run=client -o yaml > pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    env:
    - name: option # name of the env variable
      valueFrom:
        configMapKeyRef:
          name: options # name of config map
          key: var5 # name of the entity in config map
  dnsPolicy: ClusterFirst
  restartPolicy: Never
kubectl create -f pod.yaml
kubectl exec -it nginx -- sh -c "env | grep option" # will show 'option=val5'

Part 3: Secrets

1. Create a secret called mysecret with the values password=mypass

solution

kubectl create secret generic mysecret --from-literal=password=mypass

2. Get the value of mysecret

solution

kubectl get secret mysecret -o yaml
# Decode the base64 encoded value:
echo -n bXlwYXNz | base64 -d # on MAC it is -D, which decodes the value and shows 'mypass'. 
# On Windows, just use https://www.base64decode.org/ or store the value in a file and run:
certutil -decode input.txt output.txt

3. Create an nginx pod that mounts the secret mysecret in a volume on path /etc/foo

solution

kubectl run nginx --image=nginx --restart=Never -o yaml --dry-run=client > pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  volumes: # specify the volumes
  - name: foo # this name will be used for reference inside the container
    secret: # we want a secret
      secretName: mysecret # name of the secret - this must already exist on pod creation
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    volumeMounts: # our volume mounts
    - name: foo # name on pod.spec.volumes
      mountPath: /etc/foo #our mount path
  dnsPolicy: ClusterFirst
  restartPolicy: Never
kubectl create -f pod.yaml
kubectl exec -it nginx -- /bin/bash
ls /etc/foo  # shows password
cat /etc/foo/password # shows mypass

4. Delete the pod you just created and mount the variable 'password' from secret mysecret onto a new nginx pod in env variable called 'PASSWORD'

Show the environment variable using kubectl exec -it nginx -- sh -c "env | grep PASSWORD"

solution

kubectl delete pod nginx
kubectl run nginx --image=nginx --restart=Never -o yaml --dry-run=client > pod.yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    resources: {}
    env: # our env variables
    - name: PASSWORD # asked name
      valueFrom:
        secretKeyRef: # secret reference
          name: mysecret # our secret's name
          key: password # the key of the data in the secret
  dnsPolicy: ClusterFirst
  restartPolicy: Never
kubectl create -f pod.yaml
kubectl exec -it nginx -- sh -c "env | grep PASSWORD"  # will show 'PASSWORD=mypass'

Part 4: Debugging

1. Create a busybox pod that runs the command below. Check its logs.

The command that should be run is /bin/sh -c 'i=0; while true; do echo "$i: $(date)"; i=$((i+1)); sleep 1; done'.

solution

kubectl run busybox --image=busybox --restart=Never -- /bin/sh -c 'i=0; while true; do echo "$i: $(date)"; i=$((i+1)); sleep 1; done'
kubectl logs busybox -f # follow the logs

2. Create a busybox pod that runs 'ls /notexist'. Determine if there's an error (of course there is), see it. In the end, delete the pod

solution

kubectl run busybox --restart=Never --image=busybox -- /bin/sh -c 'ls /notexist'
# show that there's an error
kubectl logs busybox
kubectl describe po busybox
kubectl delete po busybox

3. Create a busybox pod that runs 'notexist'. Determine if there's an error (of course there is), see it. In the end, delete the pod forcefully with a 0 grace period

solution

kubectl run busybox --restart=Never --image=busybox -- notexist
kubectl logs busybox # will bring nothing! container never started
kubectl describe po busybox # in the events section, you'll see the error
# also...

# On Linux/Mac, run:
kubectl get events | grep -i error # you'll see the error here as well
# On Windows, run:
kubectl get events | findstr -I error

kubectl delete po busybox --force --grace-period=0

4. Get CPU/memory utilization of the nodes

solution

kubectl top nodes