输入：service mysqld start
报错：
Starting MySQL.. ERROR! The server quit without updating PID file (/usr/local/mysql/data/vm10-0-0-19.ksc.com.pid).
解决： ./scripts/mysql_install_db --user=mysql --basedir=/usr/local/mysql/ --datadir=/usr/local/mysql/data/
参考博客：在Centos上安装MySQL时出现这样的错误：Starting MySQL.. ERROR! The server quit without updating PID file (/usr/loca
输入：service mysqld start
报错：
Warning: World-writable config file '/etc/my.cnf' is ignoredStarting MySQL.Warning: World-writable config file '/etc/my.cnf' is ignored
Warning: World-writable config file '/etc/my.cnf' is ignored
ERROR! The server quit without updating PID file (/usr/local/mysql/data/vm10-0-0-19.ksc.com.pid).
出现这种情况的原因是：mysql故意不让用户重写my.cnf，权限默认是644, 即-rw-r--r--, 如果权限不是644， 则会出现这种情况。
那就改：chmod 644 /etc/my.cnf
参考博客：Warning: World-writable config file '/etc/my.cnf' is ignored
3:输入： mysql -uroot -p
报错：
Enter password:ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)
我的解决办法：ln -s /var/lib/mysql/mysql.sock /tmp/mysql.sock