Ola companeros
We have a new module, you can check the documentation at https://wiki.nethserver.org/doku.php?id=mariadb102.
The purpose is to install mariadb102 (equivalent to mysql57) and to integrate it in the backup process of Nethserver.
for now you can install it manually
yum install http://mirror.de-labrusse.fr/NethDev/nethserver-rh-mariadb102/nethserver-rh-mariadb102-0.0.4-1.ns7.sdl.noarch.rpm
to connect to mariadb102, do mysql102
Great work @stephdl ! 
I tested on a fresh 7.5 VM and it worked without problems.
I created a database, a table and some entries with phpmyadmin, made a backup-data and deleted the database.
After restore-data and restore-config my testdatabase was there again so backup/restore of mariadb102 works.
Great…
Merci infiniment @mrmarkuz
@giacomo and @davidep we need it for ejabberd, could you please check the source. For example I did a bundle and I create a table to use mariadb102 and phpmyadmin directly.
If you think it valuable we could push it as an official module
I’m looking at it, but I will need some time.
Regarding ejabberd, I’d test PostgreSQL and even SQLite before supporting MariaDB 102.
If we decide to add it, it will be the 4th supported database! A little too much for my taste 