Mount ReadWriteMany Persistent Volumes in Containers¶

You can attach a ReadWriteMany PVC to multiple containers, and that PVC can be written to, by all containers.

About this task

This example shows how a volume is claimed and mounted by each container replica of a deployment with 2 replicas, and each container replica can read and write to the PVC. It is the responsibility of an individual micro-service within an application to make a volume claim, mount it, and use it.

Prerequisites

You should refer to the Volume Claim examples. For more information, see Create ReadWriteMany Persistent Volume Claims.

Procedure

Create the busybox container with the persistent volumes created from the PVCs mounted. This deployment will create two replicas mounting the same persistent volume.

Create a yaml file definition for the busybox container.

% cat <<EOF > wrx-busybox.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: wrx-busybox
  namespace: default
spec:
  progressDeadlineSeconds: 600
  replicas: 2
  selector:
    matchLabels:
      run: busybox
  template:
    metadata:
      labels:
        run: busybox
    spec:
      containers:
      - args:
        - sh
        image: busybox
        imagePullPolicy: Always
        name: busybox
        stdin: true
        tty: true
        volumeMounts:
        - name: pvc1
          mountPath: "/mnt1"
      restartPolicy: Always
      volumes:
      - name: pvc1
        persistentVolumeClaim:
          claimName: rwx-test-claim
EOF

Apply the busybox configuration.

% kubectl apply -f wrx-busybox.yaml
deployment.apps/wrx-busybox created

Attach to the busybox and create files on the Persistent Volumes.

List the available pods.

% kubectl get pods
NAME                           READY   STATUS    RESTARTS   AGE
wrx-busybox-6455997c76-4kg8v   1/1     Running   0          108s
wrx-busybox-6455997c76-crmw6   1/1     Running   0          108s

Connect to the pod shell for CLI access.

% kubectl attach wrx-busybox-6455997c76-4kg8v -c busybox -i -t

From the container’s console, list the disks to verify that the Persistent Volume is attached.

% df
Filesystem           1K-blocks      Used Available Use% Mounted on
overlay               31441920   1783748  29658172   6% /
tmpfs                    65536         0     65536   0% /dev
tmpfs                  5033188         0   5033188   0% /sys/fs/cgroup
ceph-fuse            516542464    643072 515899392   0% /mnt1

The PVC is mounted as /mnt1.

Create files in the mount.

# cd /mnt1
# touch i-was-here-${HOSTNAME}
# ls /mnt1
i-was-here-wrx-busybox-6455997c76-4kg8vi

End the container session.

% exit
wrx-busybox-6455997c76-4kg8v -c busybox -i -t' command when the pod is running

Connect to the other busybox container

% kubectl attach wrx-busybox-6455997c76-crmw6 -c busybox -i -t

(Optional): From the container’s console list the disks to verify that the PVC is attached.

% df
Filesystem           1K-blocks      Used Available Use% Mounted on
overlay               31441920   1783888  29658032   6% /
tmpfs                    65536         0     65536   0% /dev
tmpfs                  5033188         0   5033188   0% /sys/fs/cgroup
ceph-fuse            516542464    643072 515899392   0% /mnt1

Verify that the file created from the other container exists and that this container can also write to the Persistent Volume.

# cd /mnt1
# ls /mnt1
i-was-here-wrx-busybox-6455997c76-4kg8v
# echo ${HOSTNAME}
wrx-busybox-6455997c76-crmw6
# touch i-was-here-${HOSTNAME}
# ls /mnt1
i-was-here-wrx-busybox-6455997c76-4kg8v i-was-here-wrx-busybox-6455997c76-crmw6

End the container session.

% exit
Session ended, resume using
:command:`kubectl attach wrx-busybox-6455997c76-crmw6 -c busybox -i -t`
command when the pod is running

Terminate the busybox container.
```
% kubectl delete -f wrx-busybox.yaml
```
For more information on Persistent Volume Support, see, StarlingX StarlingX Storage Configuration and Management About Persistent Volume Support.

Mount ReadWriteMany Persistent Volumes in Containers

Mount ReadWriteMany Persistent Volumes in Containers¶

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