啓動mysql時遇到The server quit without updating PID file

[root@localhost mysql]# rm -rf /etc/my.cnf
[root@localhost mysql]# ln -s my.cnf /etc/my.cnf
[root@localhost mysql]# cp ./support-files/mysql.server /etc/rc.d/init.d/mysqld
cp: overwrite ‘/etc/rc.d/init.d/mysqld’? y
[root@localhost mysql]# chmod 755 /etc/rc.d/init.d/mysqld
[root@localhost mysql]# chkconfig mysqld on
[root@localhost mysql]# vim /etc/rc.d/init.d/mysqld
[root@localhost mysql]# service mysqld start
Starting MySQL..... SUCCESS! 
[root@localhost mysql]# ps -ef | grep mysqld
root     14865 23442  0 15:49 pts/1    00:00:00 grep --color=auto mysqld
root     21705     1  0 15:48 pts/1    00:00:00 /bin/sh /usr/local/mysql/bin/mysqld_safe --datadir=/usr/local/mysql/var --pid-file=/usr/local/mysql/var/localhost.localdomain.pid
mysql    21889 21705  1 15:48 pts/1    00:00:01 /usr/local/mysql/bin/mysqld --basedir=/usr/local/mysql --datadir=/usr/local/mysql/var --plugin-dir=/usr/local/mysql/lib/plugin --user=mysql --log-error=/usr/local/mysql/var/localhost.localdomain.err --pid-file=/usr/local/mysql/var/localhost.localdomain.pid