kubernetespodspecsidecardry-run

How to create mult-container pods using --dry-run=client?


I am working on practicing for the CKAD exam and ran into an interesting problem with a multi-container pod that I can't seem to find an answer to. Lets say I run this imperative command to create a pod.yaml:

kubectl run busybox --image=busybox --dry-run=client -o yaml -- /bin/sh -c 'some commands' > pod.yaml

I then edit that yaml definition to add a sidecar nginx container with just a name and image. When I go to create this pod with

kubectl create -f pod.yaml
kubectl get pods

I get a pod with a single nginx container even though the busybox container is still defined in the pod spec yaml. I suspect this is due to something with --dry-run=client and/or running the command combined with dry run but I can't seem to find a good answer to that. Thanks in advance.

EDIT: pod.yaml

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: busybox
  name: busybox
spec:
  containers:
  - args:
    - /bin/sh
    - -c
    - while true; do echo ‘Hi I am from Main container’ >> /var/log/index.html; sleep
      5; done
    image: busybox
    name: busybox
    volumeMounts:
    - mountPath: /var/log
      name: log-vol
    image: nginx
    name: nginx
    volumeMounts:
    - mountPath: /usr/share/nginx/html
      name: log-vol
    ports:
    - containerPort: 80
  volumes:
  - name: log-vol
    emptyDir: {}
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}

Solution

  • Expanding on my comment:

    A list in YAML is a series of items marked with a leading -, like this list of strings:

    - one
    - two
    - three
    

    Or this list of dictionaries:

    containers:
      - image: busybox
        name: busybox
      - image: nginx
        name: nginx
    

    Or even this list of lists:

    outerlist:
      -
        - item 1.1
        - item 1.2
        - item 1.3
      -
        - item 2.1
        - item 2.2
        - item 2.3
    

    Your pod.yaml as written has only a single item in your containers list. You need to mark the second item:

    apiVersion: v1
    kind: Pod
    metadata:
      creationTimestamp: null
      labels:
        run: busybox
      name: busybox
    spec:
      containers:
    
      - args:
        - /bin/sh
        - -c
        - while true; do echo ‘Hi I am from Main container’ >> /var/log/index.html; sleep
          5; done
        image: busybox
        name: busybox
        volumeMounts:
        - mountPath: /var/log
          name: log-vol
    
      - image: nginx
        name: nginx
        volumeMounts:
        - mountPath: /usr/share/nginx/html
          name: log-vol
        ports:
        - containerPort: 80
      volumes:
      - name: log-vol
        emptyDir: {}
      dnsPolicy: ClusterFirst
      restartPolicy: Always