If you just uncomment the slow query log variable in mysqld.conf , you can’t start your mysql server. it’s because the variable name has changed, the following configuration works well for me.
nano /etc/mysql/mysql.conf.d/mysqld.conf # Here you can see queries with especially long duration slow_query_log = 1 slow_query_log_file = /var/log/mysql/slow-queries.log long_query_time = 1