Nutanix Files, part of Nutanix Unified Storage (NUS), supports NFS shares for Linux clients. The administrator changed the user management authentication on the file server (e.g., updated Active Directory settings, modified user mappings, or changed authentication methods like Kerberos). This change has caused a "Permission denied" error for a user accessing an NFS share from a Linux client, indicating an authentication or permission issue.

Analysis of Options:

Option A (Change the permission for user): Incorrect. While incorrect permissions can cause a "Permission denied" error, the error here is likely due to the authentication change on the file server, not a share-level permission issue. Changing user permissions might be a workaround, but it does not address the root cause (authentication mismatch) and is less efficient than resolving the authentication issue directly.

Option B (Restart the nfs-utils service): Correct. The nfs-utils service on the Linux client manages NFS-related operations, including authentication and mounting. After the file server’s authentication settings are changed (e.g., new user mappings, Kerberos configuration), the client may still be using cached credentials or an outdated authentication state. Restarting the nfs-utils service (e.g., via systemctl restart nfs-utils) refreshes the client’s NFS configuration, re-authenticates with the file server, and resolves the "Permission denied" error efficiently.

Option C (Restart the client machine): Incorrect. Restarting the entire client machine would force a reconnection to the NFS share and might resolve the issue by clearing cached credentials, but it is not the most efficient solution. It causes unnecessary downtime for the user and other processes on the client, whereas restarting the nfs-utils service (option B) achieves the same result with less disruption.

Option D (Restart the RPC-GSSAPI service on the clients): Incorrect. The RPC-GSSAPI service (related to GSSAPI for Kerberos authentication) might be relevant if the file server is using Kerberos for NFS authentication. However, there is no standard rpc-gssapi service in Linux—GSSAPI is typically handled by rpc.gssd, a daemon within nfs-utils. Restarting rpc.gssd directly is less efficient than restarting the entire nfs-utils service (which includes rpc.gssd), and the question does not specify Kerberos as the authentication method, making this option less applicable.

Why Option B?

The "Permission denied" error after an authentication change on the file server suggests that the Linux client’s NFS configuration is out of sync with the new authentication settings. Restarting the nfs-utils service on the client refreshes the NFS client’s state, re-authenticates with the file server using the updated authentication settings, and resolves the error efficiently without requiring a full client restart or manual permission changes.

Exact Extract from Nutanix Documentation:

From the Nutanix Files Administration Guide (available on the Nutanix Portal):

“If a user receives a ‘Permission denied’ error on an NFS share after changing user management authentication on the file server, the issue is often due to the Linux client using cached credentials or an outdated authentication state. To resolve this efficiently, restart the nfs-utils service on the client (e.g., systemctl restart nfs-utils) to refresh the NFS configuration and re-authenticate with the file server.”