SQL-DATABASE ERROR

Database error in WoltLab Burning Board (): Link-ID == false, connect failed
mysql error: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)
mysql error number: 2002
mysql version: unknown
php version: 5.6.40
Date: 24.09.2021 @ 15:09
Script: /profile.php?userid=3311&sid=74571c3f6cc80b92eb79d1dc9d5557e9
Referer: