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Pods

Pods

Pods are the smallest instance of an object you can deploy into k8s. Pods represent a single instances of an application. Containers are encapsulated into pods.

kubectl run nginx —image nginx

Template​

apiVersion: v1
kind: Pod
metadata:
  name: ${RESOURCE_NAME}
  # namespace: default
  labels:
    color: blue
spec:
  # nodeName: node-01
  # volumes:
  #  - name: volume-name
  #    hostPath:
  #      path: /var/lib/dir1
  containers:
    - name: ${RESOURCE_NAME}-container
      image: ${RESOURCE_NAME}:latest
      env:
        - name: APP_NAME
          value: ${RESOURCE_NAME}
      #  - name: SPECIAL_LEVEL_KEY
      #    valueFrom:
      #      configMapKeyRef:
      #        name: special-config
      #        key: special.how
      #  - name: SECRET_SOME_KEY
      #    valueFrom:
      #      secretKeyRef:
      #        name: secret-name
      #        key: fieldName
      # envFrom:
      #   - configMapRef:
      #       name: ${RESOURCE_NAME}-config
      #   - secretRef:
      #        name: ${RESOURCE_NAME}-secret
      envFrom:
        - configMapRef:
            name: configmap-name
          # prefix: CONFIG_
        - secretRef:
            name: secret-name
          # prefix: SECRETVALUE_
      # imagePullPolicy: Always
      # command: ["sleep"]
      # args: ["3600"]

---

Defining Environments​

Static set key​

env:
  - name: ENV_NAME
    value: someValue

Read a single key from an external source (configmap, secret, pod field)​

env:
  - name: ENV_FROM_CONFIGMAP
    valueFrom:
      configMapKeyRef:
        name: config-map-name
        key: the-key-in-the-config-map
  - name: ENV_FROM_SECRET
    valueFrom:
      secretKeyRef:
        name: secret-name
        key: the-key-in-the-secret
  - name: ENV_FROM_POD_FIELD
    valueFrom:
      fieldRef:
        fieldPath: # One of metadata.labels['key'], metadata.annotations['key'],
          # spec.nodeName, spec.serviceAccountName,
          # status.hostIp, status.podIP, status.podIPs

Read multiple fields into the environment​

envFrom:
   - configMapRef:
       name: configmap-name
     # prefix: CONFIG_
   - secretRef:
       name: secret-name
     # prefix: SECRETVALUE_

Multiple containers​

You CAN run multiple containers in a pod, but not for better availability. Usually this is a helper container, like a logging sidecar.

See Patterns for Composite Containers