mySql change port problem

Can't start server: Bind on TCP/IP port: Permission denied
Do you already have another mysqld server running on port: 13306 ?


Common solution is change my.cnf adding port=newport, but in what section?

Discover who is the principal executable
$locate mysqld.service

/etc/systemd/system/multi-user.target.wants/mysqld.service
/usr/lib/systemd/system/mysqld.service

$vi /usr/lib/systemd/system/mysqld.service #for watch settings
In my case, was this:
ExecStart=/usr/bin/mysqld_safe --basedir=/usr

then i know what section i need to change

$vi /etc/my.cnf  # add new port in section [mysqld_safe]

Aditional commands during process:

tail -30 /var/log/mysql/error.log

sudo lsof -i TCP:3306
netstat -lp | grep 3306
 

$systemctl status iptables.service

$service iptables status