Updates

contributors/design-proposals/propagation.md

@@ -66,8 +66,8 @@ The new `VolumeMount` will look like:
 
 ```go
 const (
-	PropagationShared  PropagationMode = "Shared"
-	PropagationSlave   PropagationMode = "Slave"
+	PropagationRShared  PropagationMode = "RShared"
+	PropagationRSlave   PropagationMode = "RSlave"
 	PropagationPrivate PropagationMode = "Private"
 )
 
@@ -83,8 +83,8 @@ type VolumeMount struct {
 }
 ```
 
-Default would be `Private`, which does not break backward compatibility,
-`Slave` and especially `Shared` must be explicitly requested.
+Default would be `RSlave`, which should not break backward compatibility,
+`RShared` must be explicitly requested.
 
 Opinion against this:
 
@@ -100,8 +100,8 @@ The new `HostPathVolumeSource` will look like:
 
 ```go
 const (
-	PropagationShared  PropagationMode = "Shared"
-	PropagationSlave   PropagationMode = "Slave"
+	PropagationRShared  PropagationMode = "RShared"
+	PropagationRSlave   PropagationMode = "RSlave"
 	PropagationPrivate PropagationMode = "Private"
 )
 
@@ -163,20 +163,31 @@ and something prevents it from starting if `/sys` is shared.
 ## Decision
 
 * We will take 'Add an option in VolumeMount API' (with an annotation during
-  alpha instead of real VolumeMount field).
+  alpha instead of real VolumeMount field):
   * With validation that it can be used only with HostPath volumes.
   * With validation that shared propagation can be used only in privileged
     containers.
+  * kubernetes/kubernetes#46444
 * Kubelet will make sure that at least `/var/lib/kubelet` can be share-able into
-  containers and it will refuse to start if it's unsuccessful.
+  containers and it will refuse to start if it's unsuccessful
+  * kubernetes/kubernetes#45724
+* Kubelet's Docker shim layer will check that it is able to run a container with
+  shared mount propagation on `/var/lib/kubelet` during startup and refuse to
+  start otherwise. This ensures that both Docker and kubelet see the same
+  `/var/lib/kubelet` and it can be shared into containers.
+  E.g. Google COS-58 runs Docker in a separate mount namespace with slave
+  propagation and thus can't run a container with shared propagation on
+  anything. Other container engines should follow the suit.
 * Node conformance suite will check that mount propagation in /var/lib/kubelet
   works.
 * During alpha, all the behavior above must be explicitly enabled by
-  `kubelet --test-enable-mount-propagation`
-  (or `kubelet --feature-gates MountPropagation=true`?). It will be used only
-  for testing of volume plugins in e2e tests. Developers / testers can enable it
-  in their clusters, but it's clearly marked as not ready for production.
+  `kubelet --experimental-enable-mount-propagation`
+  It will be used only for testing of volume plugins in e2e tests and
+  it will be marked as deprecated from the beginning.
+  Developers / testers can enable it in their clusters manually.
   Mount propagation may be redesigned or even removed in any future release.
+* The default mount propagation will be `rslave`, which is different to current
+  `private`. Extensive testing is needed!
 
 ## Extra Concerns