Automatic merge from submit-queue
Better messaging for missing volume binaries on host
**What this PR does / why we need it**:
When mount binaries are not present on a host, the error returned is a generic one.
This change is to check the mount binaries before the mount and return a user-friendly error message.
This change is specific to GCI and the flag is experimental now.
https://github.com/kubernetes/kubernetes/issues/36098
**Release note**:
Introduces a flag `check-node-capabilities-before-mount` which if set, enables a check (`CanMount()`) prior to mount operations to verify that the required components (binaries, etc.) to mount the volume are available on the underlying node. If the check is enabled and `CanMount()` returns an error, the mount operation fails. Implements the `CanMount()` check for NFS.
Sample output post change :
rkouj@rkouj0:~/go/src/k8s.io/kubernetes$ kubectl describe pods
Name: sleepyrc-fzhyl
Namespace: default
Node: e2e-test-rkouj-minion-group-oxxa/10.240.0.3
Start Time: Mon, 07 Nov 2016 21:28:36 -0800
Labels: name=sleepy
Status: Pending
IP:
Controllers: ReplicationController/sleepyrc
Containers:
sleepycontainer1:
Container ID:
Image: gcr.io/google_containers/busybox
Image ID:
Port:
Command:
sleep
6000
QoS Tier:
cpu: Burstable
memory: BestEffort
Requests:
cpu: 100m
State: Waiting
Reason: ContainerCreating
Ready: False
Restart Count: 0
Environment Variables:
Conditions:
Type Status
Initialized True
Ready False
PodScheduled True
Volumes:
data:
Type: NFS (an NFS mount that lasts the lifetime of a pod)
Server: 127.0.0.1
Path: /export
ReadOnly: false
default-token-d13tj:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-d13tj
Events:
FirstSeen LastSeen Count From SubobjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
7s 7s 1 {default-scheduler } Normal Scheduled Successfully assigned sleepyrc-fzhyl to e2e-test-rkouj-minion-group-oxxa
6s 3s 4 {kubelet e2e-test-rkouj-minion-group-oxxa} Warning FailedMount Unable to mount volume kubernetes.io/nfs/32c7ef16-a574-11e6-813d-42010af00002-data (spec.Name: data) on pod sleepyrc-fzhyl (UID: 32c7ef16-a574-11e6-813d-42010af00002). Verify that your node machine has the required components before attempting to mount this volume type. Required binary /sbin/mount.nfs is missing
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