启动mysql报错：
（一）进入/var/run/mysql目录下ll查看是否有mysqld.pid这个文件或者这个文件权限是否正确
srwxrwxrwx 1 mysql mysql 0 Jul 3 17:48 mysql.sock=
-rw-rw---- 1 mysql mysql 5 Jul 3 17:48 mysqld.pid
-rw-r--r-- 1 root root 22 Jul 3 17:48 tmpdir
修改文件的权限：（并查看属组，属主是否是mysql）
chmod 777 mysqld.pid
重启服务，测试成功。
/etc/init.d/mysql start
Starting service MySQL done
测试登录mysql是否成功：
[root@localhost mysqld]#/var/run/mysql # mysql -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.5.30-log Source distribution
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
（二）如果登录报错：
[root@localhost mysqld]# mysql -uroot -p123456
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
修改密码登陆也无效
[root@localhost mysqld]# pkill mysql
[root@localhost mysqld]# ps -ef|grep mysql
root 11644 17452 0 13:29 pts/1 00:00:00 grep mysql
不使用密码连接
root@localhost mysqld]# mysqld_safe --skip-grant-tables &
[1] 11696
以下操作参照
http://6257393.blog.51cto.com/6247393/1228380
主从同步报错
报错如下：
导致这个报错的原因可能是主键重复了，解决方法如下：
1、先到数据库log里面找到保错的position
2.再执行
