Pod

PODS

• containers are encapsulated inside pods
• horizontal scale up and down :
• add more pods - y
• add more container inside a pod - n
• add more worker nodes - n
• can have multi-container pod-1 (rare use-case)
• c1 - api
• c2 - some helper api
• both live/die together
• comm : shares same name network-namespace and storage by-default.
  • no need manually setup-
  • that's one of the benefit with pod.
• HPA horizontal pod scaling object

• k autoscale deployment deployment-1 --max=10 --cpu-percent=70

  apiVersion
  kind
  metadata
    name:pod-1
    label:
    securityContext:  # can also add container level, set user only, not capability here.
  annotation:
    secret.reloader.stakater.com/auto: "true" 
    configmap.reloader.stakater.com/auto: "true" 
    reloader.stakater.com/auto: "true"  
  spec:
  
    tolerations:
    nodeSelector:
      kubernetes.io/arch: "amd64" # arm64
      karpenter.sh/capacity-type: "spot"         <<<
  
    affinity:
      nodeAffinity:
        requiredDuringSchedulingIgnoredDuringExecution:
        preferredDuringSchedulingIgnoredDuringExecution:
        requiredDuringSchedulingRequiredDuringExecution: future
  
    mounts:
    volumes:
  
    restartPolicy: Always / Never --> container exited in pod will come up again.
    serviceAccountName: sa-1 #default  is default sa
    resources:  # better to use LimitRange object
      request:
      limit:
    initContainers:
      -
      -
    containers:
      - name: c1
        image: eg: image has ENTRYPOINT ["sleep"] & CMD ["10"]
        command: ["sleep"] ENTRYPOINT of dockerfile or --entrypoint of dcoker run ...
          - sleep
        args: ["10"] CMD of dockerfile or docker run --entrypoint <> ...
          - 10
        ports:
          - containerPort: 8080
          - containerPort: 8443
        env:
          - name:
            value :
          - name:
            valueFrom: 
              configMapKeyRef :
                - name:
                  key: 
          - name:
            valueFrom: 
              secretKeyRef: 
                - name:
                  key: 
        securityContext:  # can also add metadata level (pod level)
          runAsUser: <userid>
          capabilities: # only supported here
            add: ["MAC_ADMIN", "SYS_TIME", "NET_ADMIN"]
            drop" ["ALL"]
          allowPrivilegeEscalation: false
          runAsGroup: 101      
          runAsUser: 101
  
  
      - name: c2
        image:
  

• commands:

  - kubectl get/describe pod pod-1
  
  - kubectl get pod <pod-name> -o yaml > pod-definition.yaml
    create yml out of existing pod
  
  - kubectl edit pod <pod-name>
    - This will open the pod specification in an editor (vi editor
  
    - only the properties listed below are editable:
      spec.containers[*].image
      spec.initContainers[*].image
      spec.activeDeadlineSeconds
      spec.tolerations
      spec.terminationGracePeriodSeconds
  
    - cannot edit the environment variables, service accounts, and resource limits 
  
   option-1  :: delete and re-create
    - if we attemp to edit, non-editable feild then it will create a temp copy of yaml.
      copy of the file with your changes is saved in a temporary location.
      - kubectl delete pod pod-1    
      - kubectl create -f /tmp/kubectl-edit-ccvrq.yaml
  
   option-2  :: delete and re-create
    - kubectl get pod pod-1 -o yaml > my-new-pod.yaml
    - kubectl delete pod pod-1    
    - kubectl create -f  my-new-pod.yaml
  

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Screenshots