[Samba] How to backup data from an installation in order to restore them in a new one?

[Lm Loge]

Hello.

I appreciate the advice and maybe "revoked" is not an appropriate word, 
so I will use another one:
Machine (A) is going to be "shut down forever".

Do my questions deserve another answer given that clarification?

And, by the way, I have two DCs (a "provisioned" one and a "joined" one).
The two DCs will be "shut down forever" and replaced by two new DCs.
(Don't worry about the waste: I have the two new machines already 
available around.)

Thank you and best regards,
--
Léa