3. Compartir archivos entre dos containers en un Pod

En este laboratorio se comunicaran dos containers que viven en un mismo pod usando volumenes.

1. Crear el el pod con un volumen , y dos containers

   # save as ./two-containers-and-volume.yaml
   apiVersion: v1
   kind: Pod
   metadata:
     name: two-containers
   spec:
   
     restartPolicy: Never
   
     volumes:
     - name: shared-data
       emptyDir: {}
   
     containers:
   
     - name: nginx-container
       image: nginx
       volumeMounts:
       - name: shared-data
         mountPath: /usr/share/nginx/html
   
     - name: debian-container
       image: debian
       volumeMounts:
       - name: shared-data
         mountPath: /pod-data
       command: ["/bin/sh"]
       args: ["-c", "echo Hello from the debian container > /pod-data/index.html"]
   

   Como se puede ver se crea un Pod llamado two-containers y dentro de la especificacion se crea un volumen llamado shared-data , luego se crea un container llamado nginx-container montando el volumen en /usr/share/nginx/html, y por ultimo se crea el container llamado debian-container, montando el volumen en /pod-data. El segundo container ejecutara el siguiente comando y terminara su ejecucion.

   $ echo Hello from the debian container > /pod-data/index.html
   

   El segundo container modificara el archivo index.html de la carpeta principal del servidor nginx del segundo container, ya que este esta en el volumen compartido.

2. Crear el pod usando kubectl

   $ kubectl apply -f ./two-containers-and-volume.yaml 
     # pod/two-containers created
   

3. Para ver la informacion detallada del pod

$ kubectl get pod two-containers --output=yaml

apiVersion: v1
kind: Pod
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"name":"two-containers","namespace":"default"},"spec":{"containers":[{"image":"nginx","name":"nginx-container","volumeMounts":[{"mountPath":"/usr/share/nginx/html","name":"shared-data"}]},{"args":["-c","echo Hello from the debian container \u003e /pod-data/index.html"],"command":["/bin/sh"],"image":"debian","name":"debian-container","volumeMounts":[{"mountPath":"/pod-data","name":"shared-data"}]}],"restartPolicy":"Never","volumes":[{"emptyDir":{},"name":"shared-data"}]}}
  creationTimestamp: "2022-06-16T14:26:55Z"
  name: two-containers
  namespace: default
  resourceVersion: "35653"
  uid: a2f25f74-e860-465d-b0e9-1fbdfa9d8a1a
spec:
  containers:
  - image: nginx
    imagePullPolicy: Always
    name: nginx-container
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /usr/share/nginx/html
      name: shared-data
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-mvrgj
      readOnly: true
  - args:
    - -c
    - echo Hello from the debian container > /pod-data/index.html
    command:
    - /bin/sh
    image: debian
    imagePullPolicy: Always
    name: debian-container
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /pod-data
      name: shared-data
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-mvrgj
      readOnly: true
  dnsPolicy: ClusterFirst
  enableServiceLinks: true
  nodeName: minikube
  preemptionPolicy: PreemptLowerPriority
  priority: 0
  restartPolicy: Never
  schedulerName: default-scheduler
  securityContext: {}
  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds: 30
  tolerations:
  - effect: NoExecute
    key: node.kubernetes.io/not-ready
    operator: Exists
    tolerationSeconds: 300
  - effect: NoExecute
    key: node.kubernetes.io/unreachable
    operator: Exists
    tolerationSeconds: 300
  volumes:
  - emptyDir: {}
    name: shared-data
  - name: kube-api-access-mvrgj
    projected:
      defaultMode: 420
      sources:
      - serviceAccountToken:
          expirationSeconds: 3607
          path: token
      - configMap:
          items:
          - key: ca.crt
            path: ca.crt
          name: kube-root-ca.crt
      - downwardAPI:
          items:
          - fieldRef:
              apiVersion: v1
              fieldPath: metadata.namespace
            path: namespace
status:
  conditions:
  - lastProbeTime: null
    lastTransitionTime: "2022-06-16T14:26:55Z"
    status: "True"
    type: Initialized
  - lastProbeTime: null
    lastTransitionTime: "2022-06-16T14:26:55Z"
    message: 'containers with unready status: [debian-container]'
    reason: ContainersNotReady
    status: "False"
    type: Ready
  - lastProbeTime: null
    lastTransitionTime: "2022-06-16T14:26:55Z"
    message: 'containers with unready status: [debian-container]'
    reason: ContainersNotReady
    status: "False"
    type: ContainersReady
  - lastProbeTime: null
    lastTransitionTime: "2022-06-16T14:26:55Z"
    status: "True"
    type: PodScheduled
  containerStatuses:
  - containerID: docker://fc3b98f854b9bb2a26c6abbe9879bffa4ae93ee16907aa725a99a5f90699a3c5
    image: debian:latest
    imageID: docker-pullable://debian@sha256:3f1d6c17773a45c97bd8f158d665c9709d7b29ed7917ac934086ad96f92e4510
    lastState: {}
    name: debian-container
    ready: false # (1)
    restartCount: 0
    started: false
    state:
      terminated:
        containerID: docker://fc3b98f854b9bb2a26c6abbe9879bffa4ae93ee16907aa725a99a5f90699a3c5
        exitCode: 0
        finishedAt: "2022-06-16T14:27:00Z"
        reason: Completed # (2)
        startedAt: "2022-06-16T14:27:00Z"
  - containerID: docker://00c92009ff5b762f5a26552f1515addbe118403ab4efbb1e2d1244c698f0ccb2
    image: nginx:latest
    imageID: docker-pullable://nginx@sha256:2bcabc23b45489fb0885d69a06ba1d648aeda973fae7bb981bafbb884165e514
    lastState: {}
    name: nginx-container
    ready: true
    restartCount: 0
    started: true
    state:
      running:
        startedAt: "2022-06-16T14:26:57Z"
  hostIP: 192.168.39.232
  phase: Running # (3)
  podIP: 172.17.0.16
  podIPs:
  - ip: 172.17.0.16
  qosClass: BestEffort
  startTime: "2022-06-16T14:26:55Z"

1. Es false debido a que el contenedor solo ejecuta un echo y termina su ejecucion.

2. El container termino su ejecucion con exito.

3. El container nginx esta corriendo porque es un servidor.

Se puede ver que container debian-container termino su ejecucion y nginx-container sigue corriendo.

1. Entrar al contenedor nginx-container

   $ kubectl exec -it two-containers -c nginx-container -- /bin/bash
   

2. Revisar el archivo index.html de la carpeta compartida

   root@two-containers:/# cat /usr/share/nginx/html/index.html 
     # Hello from the debian container
   

3. Revisar la respuesta del servidor de nginx

   root@two-containers:/# curl localhost
     # Hello from the debian container
   

{"data":{"attributes":{"resource_names_by_hash":{"7d74f4592a9fd6ff":"POST businessloki.loki.svc.cluster.local:3100/loki/api/v1/push","5fc09ce97131f406":"POST dc.services.visualstudio.com/v2/track","424ed4ae196ebbaf":"POST rt.services.visualstudio.com/QuickPulseService.svc/ping"}},"type":"resource_names_by_hash"}}