EDIT: they fixed their official documentation

Official Cisco documentation about setting up NFS server for DNA center is here. The problem is, this is for Ubuntu, and Ubuntu has different names for group “nobody” than CentOS.

So if you get an error saying:

BACKUP.ndp:elasticsearch
FAILURE
Exception
Task error description:
Error during _process_backup(): Internal server error: {"error":{"root_cause":[{"type":"snapshot_creation_exception",
"reason":"[ndp:e522e20b-69e3-45b0-b20c-20138ba1444c.000/AGvhN1eCRH6CtE60mNl3KA] failed to create snapshot"}],"type":"
snapshot_creation_exception","reason":"[ndp:e522e20b-69e3-45b0-b20c-20138ba1444c.000/AGvhN1eCRH6CtE60mNl3KA] failed to
create snapshot","caused_by":{"type":"access_denied_exception","reason":"/var/data/es/snapshots/meta-AGvhN1eCRH6CtE60mNl3KA.dat"}},"status":500}

That means you have the wrong user and group set up on server NFS directory.

For Ubuntu:

chown nobody:nogroup /dir/to/nfs/share

For CentOS:

chown nfsnobody:nfsnobody /dir/to/nfs/share