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 must have created the PVCs. This procedure uses PVCs with names and configurations created in StarlingX StarlingX Storage Configuration and Management: 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.
~(keystone_admin)]$ 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.
~(keystone_admin)]$ 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.
~(keystone_admin)]$ kubectl get pods NAME READY STATUS RESTARTS AGE wrx-busybox-767564b9cf-g8ln8 1/1 Running 0 49s wrx-busybox-767564b9cf-jrk5z 1/1 Running 0 49s
Connect to the pod shell for CLI access.
kubectl attach wrx-busybox-767564b9cf-g8ln8 -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 9695488 21746432 31% / tmpfs 65536 0 65536 0% /dev tmpfs 12295352 0 12295352 0% /sys/fs/cgroup 192.168.204.2:6789:/volumes/csi/pvc-volumes-565a1160-7b6c-11ed-84b8-0e99d59ed96d/cf39026c-06fc-413a-bce9-b13fb66254a3 1048576 0 1048576 0% /mnt1
The PVC is mounted as /mnt1.
Create files in the mount.
# cd /mnt1 # touch i-was-here-${HOSTNAME} # ls /mnt1 i-was-here-wrx-busybox-767564b9cf-g8ln8
End the container session.
% exit Session ended, resume using 'kubectl attach wrx-busybox-767564b9cf-g8ln8 -c busybox -i -t' command when the pod is running
Connect to the other busybox container
~(keystone_admin)]$ kubectl attach wrx-busybox-767564b9cf-jrk5z -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 9695512 21746408 31% / tmpfs 65536 0 65536 0% /dev tmpfs 12295352 0 12295352 0% /sys/fs/cgroup 192.168.204.2:6789:/volumes/csi/pvc-volumes-565a1160-7b6c-11ed-84b8-0e99d59ed96d/cf39026c-06fc-413a-bce9-b13fb66254a3 1048576 0 1048576 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 i-was-here-wrx-busybox-767564b9cf-g8ln8 # echo ${HOSTNAME} wrx-busybox-767564b9cf-jrk5z # touch i-was-here-${HOSTNAME} # ls i-was-here-wrx-busybox-767564b9cf-g8ln8 i-was-here-wrx-busybox-767564b9cf-jrk5z
End the container session.
% exit Session ended, resume using 'kubectl attach wrx-busybox-767564b9cf-jrk5z -c busybox -i -t' command when the pod is running
Terminate the busybox container.
~(keystone_admin)]$ kubectl delete -f wrx-busybox.yaml
For more information on Persistent Volume Support, see, About Persistent Volume Support.