mysql [ERROR] Can't create IP socket: Permission denied

/***************************************************************************
 *       mysql [ERROR] Can't create IP socket: Permission denied
 * 说明：
 *     在嵌入式方面的，这种权限问题还是挺大的，而且有时候还不好找。
 *
 *                                         2016-9-27 深圳 南山平山村 曾剑锋
 **************************************************************************/

一、错误现象：
    cat /var/mysql/mysql.err
        700101 00:01:09 mysqld_safe Starting mysqld daemon with databases from /var/mysql
        700101  0:01:09 [Warning] '--skip-locking' is deprecated and will be removed in a future release. Please use '--skip-external-locking' instead.
        700101  0:01:09 [Note] Event Scheduler: Loaded 0 events
        700101  0:01:09 [Note] /usr/libexec/mysqld: ready for connections.
        Version: '5.1.73-log'  socket: '/tmp/mysql.sock'  port: 3306  Source distribution
        000101 00:06:42 mysqld_safe Starting mysqld daemon with databases from /var/mysql
        000101  0:06:42 [Warning] '--skip-locking' is deprecated and will be removed in a future release. Please use '--skip-external-locking' instead.
        000101  0:06:42 [ERROR] Can't create IP socket: Permission denied
        000101  0:06:42 [ERROR] Aborting

        000101  0:06:42 [Note] /usr/libexec/mysqld: Shutdown complete

        000101 00:06:42 mysqld_safe mysqld from pid file /run/mysql/mysqld.pid ended

二、原因：
    应该是mysqld的执行用户是mysql，然后无法使用root权限的内容。

三、解决办法：
    cat /etc/my.cnf
        ......
        # The MySQL server
        [mysqld]
        ......
        user=root
        ......