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State Persistence (8%)

Define volumes

Create busybox pod with two containers, each one will have the image busybox and will run the 'sleep 3600' command. Make both containers mount an emptyDir at '/etc/foo'. Connect to the second busybox, write the first column of '/etc/passwd' file to '/etc/foo/passwd'. Connect to the first busybox and write '/etc/foo/passwd' file to standard output. Delete pod.

show

This question is probably a better fit for the 'Multi-container-pods' section but I'm keeping it here as it will help you get acquainted with state

Easiest way to do this is to create a template pod with:

kubectl run busybox --image=busybox --restart=Never -o yaml --dry-run -- /bin/sh -c 'sleep 3600' > pod.yaml
vi pod.yaml

Copy paste the container definition and type the lines that have a comment in the end:

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: busybox
  name: busybox
spec:
  dnsPolicy: ClusterFirst
  restartPolicy: Never
  containers:
  - args:
    - /bin/sh
    - -c
    - sleep 3600
    image: busybox
    imagePullPolicy: IfNotPresent
    name: busybox
    resources: {}
    volumeMounts: #
    - name: myvolume #
      mountPath: /etc/foo #
  - args:
    - /bin/sh
    - -c
    - sleep 3600
    image: busybox
    name: busybox2 # don't forget to change the name during copy paste, must be different from the first container's name!
    volumeMounts: #
    - name: myvolume #
      mountPath: /etc/foo #
  volumes: #
  - name: myvolume #
    emptyDir: {} #
status: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Never

Connect to the second container:

kubectl exec -it busybox -c busybox2 -- /bin/sh
cat /etc/passwd | cut -f 1 -d ':' > /etc/foo/passwd 
cat /etc/foo/passwd # confirm that stuff has been written successfully
exit

Connect to the first container:

kubectl exec -it busybox -c busybox -- /bin/sh
mount | grep foo # confirm the mounting
cat /etc/foo/passwd
exit
kubectl delete po busybox

Create a PersistentVolume of 10Gi, called 'myvolume'. Make it have accessMode of 'ReadWriteOnce' and 'ReadWriteMany', storageClassName 'normal', mounted on hostPath '/etc/foo'. Save it on pv.yaml, add it to the cluster. Show the PersistentVolumes that exist on the cluster

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vi pv.yaml
kind: PersistentVolume
apiVersion: v1
metadata:
  name: myvolume
spec:
  storageClassName: normal
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
    - ReadWriteMany
  hostPath:
    path: /etc/foo

Show the PersistentVolumes:

kubectl create -f pv.yaml
# will have status 'Available'
kubectl get pv

Create a PersistentVolumeClaim for this storage class, called mypvc, a request of 4Gi and an accessMode of ReadWriteOnce and save it on pvc.yaml. Create it on the cluster. Show the PersistentVolumeClaims of the cluster. Show the PersistentVolumes of the cluster

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vi pvc.yaml
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: mypvc
spec:
  storageClassName: normal
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 4Gi

Create it on the cluster:

kubectl create -f pvc.yaml

Show the PersistentVolumeClaims and PersistentVolumes:

kubectl get pvc # will show as 'Bound'
kubectl get pv # will show as 'Bound' as well

Create a busybox pod with command 'sleep 3600', save it on pod.yaml. Mount the PersistentVolumeClaim to '/etc/foo'. Connect to the 'busybox' pod, and copy the '/etc/passwd' file to '/etc/foo'

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Create a skeleton pod:

kubectl run busybox --image=busybox --restart=Never -o yaml --dry-run -- /bin/sh -c 'sleep 3600' > pod.yaml
vi pod.yaml

Add the lines that finish with a comment:

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: busybox
  name: busybox
spec:
  containers:
  - args:
    - /bin/sh
    - -c
    - sleep 3600
    image: busybox
    imagePullPolicy: IfNotPresent
    name: busybox
    resources: {}
    volumeMounts: #
    - name: myvolume #
      mountPath: /etc/foo #
  dnsPolicy: ClusterFirst
  restartPolicy: Never
  volumes: #
  - name: myvolume #
    persistentVolumeClaim: #
      claimName: mypvc #
status: {}

Create the pod:

kubectl create -f pod.yaml

Connect to the pod and copy '/etc/passwd' to '/etc/foo/passwd':

kubectl exec busybox -it -- cp /etc/passwd /etc/foo/passwd

Create a second pod which is identical with the one you just created (you can easily do it by changing the 'name' property on pod.yaml). Connect to it and verify that '/etc/foo' contains the 'passwd' file. Delete pods to cleanup

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Create the second pod, called busybox2:

vim pod.yaml
# change 'name: busybox' to 'name: busybox2'
kubectl create -f pod.yaml
kubectl exec busybox2 -- ls /etc/foo # will show 'passwd'
# cleanup
kubectl delete po busybox busybox2

Create a busybox pod with 'sleep 3600' as arguments. Copy '/etc/passwd' from the pod to your local folder

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kubectl run busybox --image=busybox --restart=Never -- sleep 3600
kubectl cp busybox:/etc/passwd . # kubectl cp command
cat passwd