create/write permission denied – mysql/mariadb/libman etc. – howto fix broken linux filesystem permissions with valid backup

after a reboot i could not start mysql anymore. [ERROR] mysqld: Can’t create/write to file ‘/usr/local/var/mysql/aria_log_control’ after a while i noticed that man was not working anymore: man-db: error while loading shared libraries: libmandb-2.8.1.so slowly i started to understand that something serious did happen to the system. after executing chmod o+x . from / directory,…