Hummm now the server is working again.
About the "garbage", I read something about i-mscp 1.1.14 and a problem with the cron job.
It was fixed with the 1.1.15 if I have good memory
About the right of /... I don't kown what to say.
I tried to reinstall mysql/mariadb, but I didn't "play with fire"...
Anycase, thanks for looking : the server is running now. I will probably reinstall everything during next days....