[KEP-4639] Graduate image volume source to beta

Update the documentation to reflect the graduated feature.

Signed-off-by: Sascha Grunert <sgrunert@redhat.com>

content/en/docs/concepts/storage/volumes.md

@@ -628,8 +628,10 @@ volume with file execution blocked (`noexec`).
 
 Besides that:
 
-- Sub path mounts for containers are not supported
-  (`spec.containers[*].volumeMounts.subpath`).
+- [`subPath`](/docs/concepts/storage/volumes/#using-subpath) or
+  [`subPathExpr`](/docs/concepts/storage/volumes/#using-subpath-expanded-environment)
+  mounts for containers (`spec.containers[*].volumeMounts.[subPath,subPathExpr]`)
+  are only supported from Kubernetes v1.33.
 - The field `spec.securityContext.fsGroupChangePolicy` has no effect on this
   volume type.
 - The [`AlwaysPullImages` Admission Controller](/docs/reference/access-authn-authz/admission-controllers/#alwayspullimages)

content/en/docs/reference/command-line-tools-reference/feature-gates/ImageVolume.md

@@ -9,6 +9,10 @@ stages:
   - stage: alpha
     defaultValue: false
     fromVersion: "1.31"
+    toVersion: "1.32"
+  - stage: beta
+    defaultValue: false
+    fromVersion: "1.33"
 ---
 Allow using the [`image`](/docs/concepts/storage/volumes/) volume source in a Pod.
 This volume source lets you mount a container image as a read-only volume.

content/en/docs/tasks/configure-pod-container/image-volumes.md

@@ -67,6 +67,39 @@ to a valid reference and consuming it in the `volumeMounts` of the container. Fo
    2
    ```
 
+## Use `subPath` (or `subPathExpr`)
+
+It is possible to utilize
+[`subPath`](/docs/concepts/storage/volumes/#using-subpath) or
+[`subPathExpr`](/docs/concepts/storage/volumes/#using-subpath-expanded-environment)
+from Kubernetes v1.33 when using the image volume feature.
+
+{{% code_sample file="pods/image-volumes-subpath.yaml" %}}
+
+1. Create the pod on your cluster:
+
+   ```shell
+   kubectl apply -f https://k8s.io/examples/pods/image-volumes-subpath.yaml
+   ```
+
+1. Attach to the container:
+
+   ```shell
+   kubectl attach -it image-volume bash
+   ```
+
+1. Check the content of the file from the `dir` sub path in the volume:
+
+   ```shell
+   cat /volume/file
+   ```
+
+   The output is similar to:
+
+   ```none
+   1
+   ```
+
 ## Further reading
 
 - [`image` volumes](/docs/concepts/storage/volumes/#image)

content/en/examples/pods/image-volumes-subpath.yaml

@@ -0,0 +1,18 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: image-volume
+spec:
+  containers:
+  - name: shell
+    command: ["sleep", "infinity"]
+    image: debian
+    volumeMounts:
+    - name: volume
+      mountPath: /volume
+      subPath: dir
+  volumes:
+  - name: volume
+    image:
+      reference: quay.io/crio/artifact:v1
+      pullPolicy: IfNotPresent