Troubleshooting: RWX Volume Fails to Be Attached Caused by `Protocol not supported`

Derek Su | October 27, 2023

Applicable versions

All Longhorn versions.


Attempts to attach an RWX volume are unsuccessful, and the workload using the volume is unable to start. The logs contain the following messages:

Oct 11 07:42:23 dev-worker-1 k3s[1294]: Mounting command: /usr/local/sbin/nsmounter
Oct 11 07:42:23 dev-worker-1 k3s[1294]: Mounting arguments: mount -t nfs -o vers=4.1,noresvport,intr,hard /var/lib/kubelet/plugins/
Oct 11 07:42:23 dev-worker-1-autoscaled-small-19baf778f50efd8c k3s[1294]: Output: mount.nfs: Protocol not supported for on /var/lib/kubelet/plugins/

The issue applies to RWX volumes on hosts running OpenSUSE MicroOS (from 2023/10/08 to 2023/10/21) and other distributions using version 6.5.6 of the Linux kernel.


The cause of this issue is a regression of the NFS protocol in Linux kernel 6.5.6. Because of the regression, NFS clients are unable to connect to an NFS server inside a share manager pod.


To address the issue, you can perform the following actions:

  1. Upgrade the operating system to a version using Linux kernel 6.5.7 or later.
  2. Downgrade the operating system to a version using Linux kernel 6.5.5 or earlier.

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