Multi-Container Pods (10%)
Practice questions based on these concepts
- Understand Multi-container pod design patterns (eg: ambassador, adaptor, sidecar)
Questions
Create a Pod with three busy box containers with commands “ls; sleep 3600;”, “echo Hello World; sleep 3600;” and “echo this is the third container; sleep 3600” respectively and check the status
// first create single container pod with dry run flag
kubectl run busybox --image=busybox --restart=Never --dry-run -o yaml -- bin/sh -c "sleep 3600; ls" > multi-container.yaml
// edit the pod like below
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: busybox
name: busybox
spec:
containers:
- args:
- bin/sh
- -c
- ls; sleep 3600
image: busybox
name: busybox1
resources: {}
- args:
- bin/sh
- -c
- echo Hello world; sleep 3600
image: busybox
name: busybox2
resources: {}
- args:
- bin/sh
- -c
- echo this is third container; sleep 3600
image: busybox
name: busybox3
resources: {}
dnsPolicy: ClusterFirst
restartPolicy: Never
status: {}
// create it
kubectl create -f multi-container.yaml
kubectl get po busybox
Check the logs of each container that you just created
kubectl logs busybox -c busybox1
kubectl logs busybox -c busybox2
kubectl logs busybox -c busybox3
Check the previous logs of the second container busybox2 if any
kubectl logs busybox -c busybox2 --previous
Run command ls in the third container busybox3 of the above pod
kubectl exec busybox -c busybox3 -- ls
Show metrics of the above pod containers and puts them into the file.log and verify
kubectl top pod busybox --containers
// putting them into file
kubectl top pod busybox --containers > file.log
cat file.log
Create a Pod with main container busybox and which executes this “while true; do echo ‘Hi I am from Main container’ >> /var/log/index.html; sleep 5; done” and with sidecar container with nginx image which exposes on port 80. Use emptyDir Volume and mount this volume on path /var/log for busybox and on path /usr/share/nginx/html for nginx container. Verify both containers are running.
// create an initial yaml file with this
kubectl run multi-cont-pod --image=busbox --restart=Never --dry-run -o yaml > multi-container.yaml
// edit the yml as below and create it
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: multi-cont-pod
name: multi-cont-pod
spec:
volumes:
- name: var-logs
emptyDir: {}
containers:
- image: busybox
command: ["/bin/sh"]
args: ["-c", "while true; do echo 'Hi I am from Main container' >> /var/log/index.html; sleep 5;done"]
name: main-container
resources: {}
volumeMounts:
- name: var-logs
mountPath: /var/log
- image: nginx
name: sidecar-container
resources: {}
ports:
- containerPort: 80
volumeMounts:
- name: var-logs
mountPath: /usr/share/nginx/html
dnsPolicy: ClusterFirst
restartPolicy: Never
status: {}
kubectl create -f multi-container.yaml
kubectl get po multi-cont-pod
Exec into both containers and verify that main.txt exist and query the main.txt from sidecar container with curl localhost
// exec into main container
kubectl exec -it multi-cont-pod -c main-container -- sh
cat /var/log/main.txt
// exec into sidecar container
kubectl exec -it multi-cont-pod -c sidecar-container -- sh
cat /usr/share/nginx/html/index.html
// install curl and get default page
kubectl exec -it multi-cont-pod -c sidecar-container -- sh
# apt-get update && apt-get install -y curl
# curl localhost
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