MySQL无法启动问题解决Warning: World-writable config file ‘/etc/my.cnf’ is ignored

今天重启一台内网服务器，发现mysql无法正常重启，执行systemctl start mysql，报错如下

    Starting LSB: start and stop MySQL...
    Dec 11 14:24:42 localhost.localdomain mysql[32329]: my_print_defaults: [Warning] World-writable config file '/etc/my.cnf' is ignored.
    Dec 11 14:24:42 localhost.localdomain mysql[32329]: Starting MySQL.my_print_defaults: [Warning] World-writable config file '/etc/my.cnf' is ignored.
    Dec 11 14:24:42 localhost.localdomain mysql[32329]: my_print_defaults: [Warning] World-writable config file '/etc/my.cnf' is ignored.
    Dec 11 14:24:42 localhost.localdomain mysql[32329]: Logging to '/usr/local/mysql/data/localhost.localdomain.err'.
    Dec 11 14:24:43 localhost.localdomain mysql[32329]: ERROR! The server quit without updating PID file (/usr/local/mysql/data/localhost.localdomain.pid).
    Dec 11 14:24:43 localhost.localdomain systemd[1]: mysql.service: control process exited, code=exited status=1

刚开始关注点放在了 ERROR! The server quit without updating PID file (/usr/local/mysql/data/localhost.localdomain.pid). 这里，发现mysql下没有data这个文件夹，以为数据库文件丢失了呢，头疼。
后来将关注点放到 my_print_defaults: [Warning] World-writable config file '/etc/my.cnf' is ignored.
- 查看my.cnf的权限，
- ls -l /etc/my.cnf
- -rwxrwxrwx 1 root root 1404 Oct 16 19:31 /etc/my.cnf ，发现是777权限
- chmod 644 /etc/my.cnf ，设置为644权限
- systemctl start mysql ，一切OK
另外，发现无法远程连接，之前设置过IP，用户访问权限，但还是重新设置了一遍，并开放端口3306，才可以远程连接（由于设置权限和开放端口没有分开执行，所以并未确定是端口还是权限造成的）。

    GRANT ALL PRIVILEGES ON *.* TO 'username '@'%' IDENTIFIED BY 'password' WITH GRANT OPTION;

    FLUSH   PRIVILEGES;

    iptables -I INPUT -p tcp --dport 3306-j ACCEPT
    
    远程连接成功