Kubernetes PersistentVolume - Backup /data

Ignition
11

Just augmenting this thread for those that find it (since I had a couple questions on this topic, recently)… In K8s, you can leverage initContainers to seed the data volume prior to initial launch of the Gateway container [in the pod].

Here is an example deployment that leverages an init container to seed the data volume with files from the image:

# Ignition K8s Example Deployment
---
# Deployment
apiVersion: apps/v1
kind: Deployment
metadata:
  name: ignition-deployment
spec:
  selector:
    matchLabels:
      app: ignition-app
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: ignition-app
    spec:
      initContainers:
      - name: seed-volume
        image: inductiveautomation/ignition:8.1.17
        resources:
          limits:
            memory: "256Mi"
            cpu: "1000m"
        command:
        - sh
        - -c
        - >
          if [ ! -f /data/.ignition-seed-complete ]; then
            touch /data/.ignition-seed-complete ;
            cp -dpR /usr/local/bin/ignition/data/* /data/ ;
          fi
        volumeMounts:
        - mountPath: /data
          name: ignition-data
      containers:
      - name: ignition
        image: inductiveautomation/ignition:8.1.17
        resources:
          limits:
            memory: "2048Mi"
            cpu: "1000m"
        args:
        - -n
        - Ignition-k8s
        - -m
        - "2048"
        env:
        - name: ACCEPT_IGNITION_EULA
          value: "Y"
        - name: GATEWAY_ADMIN_PASSWORD_FILE
          value: /run/secrets/gateway-admin/password
        - name: IGNITION_EDITION
          value: standard
        ports:
        - name: ignition-web
          containerPort: 8088
        volumeMounts:
        - mountPath: /usr/local/bin/ignition/data
          name: ignition-data
        - mountPath: /run/secrets/gateway-admin
          name: gateway-admin
          readOnly: true
        readinessProbe:
          exec:
            command:
            - health-check.sh
            - -t
            - "3"
          initialDelaySeconds: 60
          periodSeconds: 10
          failureThreshold: 10
          timeoutSeconds: 3
      volumes:
      - name: ignition-data
        persistentVolumeClaim:
          claimName: ignition-pv-claim
      - name: gateway-admin
        secret:
          secretName: gateway-admin

---
# Secret (which you wouldn't normally just have hanging out here in your deployment yaml)
apiVersion: v1
kind: Secret
metadata:
  name: gateway-admin
type: Opaque
data:
  password: UEBzc3cwcmQ=
---
# Service
apiVersion: v1
kind: Service
metadata: 
  name: ignition-lb
spec:
  selector:
    app: ignition-app
  type: LoadBalancer
  ports:
    - name: http
      port: 8088
      targetPort: 8088
---
# PersistentVolume
apiVersion: v1
kind: PersistentVolume
metadata:
  name: ignition-pv-volume
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 10Gi
  hostPath:
    path: "${PWD}/ignition-data"
  accessModes:  # ideally we want ReadWriteOncePod, but still in alpha?
    - ReadWriteOnce
---
# PersistentVolumeClaim
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: ignition-pv-claim
spec:
  storageClassName: manual
  resources:
    requests:
      storage: 3Gi
  accessModes:
    - ReadWriteOnce

This is designed to be run from a folder on your host system with a fresh (and empty, initially) ignition-data subfolder. I use envsubst to substitute the current working directory. So you could deploy this with, for example:

$ kubectl create ns k8s-testing
$ kubectl config set-context --current --namespace=k8s-testing
$ envsubst < ignition-app.yaml | kubectl apply -f -

Keep in mind that this is just an example deployment that you can test locally, not a production-ready configuration.

Here’s a little video to check out with this too, in the event that moving pictures>pictures>words. :grinning:
k8s-testing-2.mp4

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