[Samba] Samba filesystem layout

[Marco Coli]

Hello, in the latest versions (I am not sure when) the layout of samba 
files, related to dns, has changed.
Previously (using sernet rpms on RHEL/CentOS) there was 
/var/lib/samba/private/dns, recently /var/lib/samba/bind-dns.

This change was helpful, because at every rpm update the permission of 
"private" were restored to root:root 0700, preventing bind to enter 
inside to reach dns info, and requiring a manual adjustment of permission.

For all new installation, the new layout is applied, but I have several 
AD machines installed with 4.X old layout, upgraded in time to 4.12.x, 
where dns stuff remained internal to private.

Which are the correct steps to migrate to new layout?

Thank you.