Nutanix AHV backup failed with error Failing to mount the snapshot. "Failed to mount path /usr/openv/tmp/ntxmnt"

Problem

Nutanix Acropolis Hypervisor (AHV) VMware backups can result with a failed job ending with status code status 6, if the snapshot fails to mount to the backup host.

This is despite that the required IP address of the NetBackup backup host is included in the trusted whitelist setting of the Nutanix Prism host.

Error Message

Failed to mount path /usr/openv/tmp/ntxmnt

NetBackup Job Details show:

29 Jul, 2021 8:09:18 PM - Critical bpbrm (pid=15928) from client TESTBACKUP: FTL - Failed to mount path /usr/openv/tmp/ntxmnt/cd999050-1234-4b2a-9cd7-56543f50e6ab/server/.snapshot/16/161307-1234308546200150-50070216/.acropolis/vmdisk. Refer to the documentation for more information.

29 Jul, 2021 8:09:18 PM - Warning bpbrm (pid=15928) from client TESTBACKUP: WRN -Unable to unmount the container [CONTAINERNAME] 

You must manually unmount the container from the backup host. For more information, refer to the <bpbkar> logs.

29 Jul, 2021 8:09:18 PM - Critical bpbrm (pid=15928) from client TESTBACKUP: FTL - cleanup() failed, status 6

Cause

Nutanix Whitelist settings are set at the container level, and when configured they will override the whitelist settings applied at a Global level.

• A whitelist is a set of addresses that are allowed access to the cluster.
• Whitelists are used to allow appropriate traffic when unauthorized access from other sources is denied.

Solution

1. Navigate to Advanced Settings from the Nutanix Prism Web Management Console:

Home > Storage > Select container > Update Storage container > Advanced Settings

2. For each defined storage container, there is a file system white list setting which will override the global file system white list settings.

• Verify each configured setting that has been added to the whitelist entry list.
• An NFS whitelist is created when the hypervisor is ESXi or AHV.
• A CIFS whitelist is created when the hypervisor is Hyper-V.