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ReadWriteOncePod

As explained in Kubernetes in Action, Second Edition

ReadWriteOncePod is a Kubernetes volume access mode that permits a volume to be mounted read-write by only one pod at a time.

ReadWriteOncePod (RWOP) is a Kubernetes volume access mode that permits one pod across the entire cluster to mount a volume for reading and writing. A PersistentVolumeClaim requests this mode when only one pod instance should use the volume at a time. section 10.2.4 section 10.2.1

Use RWOP to establish an exclusive pod-level storage relationship:

  • The volume attaches to one node and mounts into one pod, which can both read and write its files. section 10.2.4
  • A second pod using the same PersistentVolumeClaim remains Pending because simultaneous use is forbidden. section 10.2.4
  • Do not confuse RWOP with ReadWriteOnce: ReadWriteOnce permits multiple pods on the same node, while RWOP permits only one pod cluster-wide. section 10.2.4 section 10.2.1

Requesting exclusive access for a quiz database

A claim can request RWOP with `accessModes: [ReadWriteOncePod]` and `storage: 1Gi`. A quiz pod then mounts the claim into its MongoDB container. After binding, `kubectl get pvc quiz-data` reports access mode `RWOP`; deleting the pod leaves the claim available for reuse in another pod. section 10.2.1 section 10.2.2

$ kubectl get pods
NAME    READY   STATUS    RESTARTS   AGE
quiz    2/2     Running   0          20m
quiz2   0/2     Pending   0          12m

Inspect the expected Pending status when a second pod attempts to use the same RWOP claim. section 10.2.4

How Kubernetes in Action, Second Edition covers it

How deep it goes
Defines cluster-wide pod exclusivity, demonstrates Pending scheduling, and contrasts node-level ReadWriteOnce without discussing storage-driver internals.
Examples
Uses a quiz database claim, a MongoDB-mounted pod, and a second pod that remains Pending.
What it assumes
Assumes basic pods and PersistentVolumeClaims while defining access modes and showing how a claim mounts into a pod.
What you can do after
Apply it via kubectl and a PersistentVolumeClaim manifest, then verify RWOP binding and diagnose competing pods through status or events.
How it connects
Connects PersistentVolumeClaim, PersistentVolume, StorageClass, pod scheduling, and ReadWriteOnce.
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This explainer was generated by Manning's knowledge graph from the text of Kubernetes in Action, Second Edition. The section links point to the parts of the book it draws on.