Mysql 主从数据库同步(centos篇)
切换主从服务器
当主服务器出现故障时，可将从服务器当主服务器来使用.步骤如下:
1、保证所有从数据库都已经执行了relay log中的全部更新，在从服务器中执行
stop slave io_thread,用show processlist检查，查看状态是否是Has read all relay log,表示更新完成.
mysql>stop slave io_thread;
Query OK,0 affected (0.00 sec)
mysql>show processlistG;
Query OK,0 affected (0.00 sec)
mysql>show processlistG;
*************************** 2. row ***************************
Id: 2
User: system user
Host:
db: NULL
Command: Connect
Time: 4757
State: Has read all relay log; waiting for the slave I/O thread to update it
Info: NULL
Id: 2
User: system user
Host:
db: NULL
Command: Connect
Time: 4757
State: Has read all relay log; waiting for the slave I/O thread to update it
Info: NULL
2、在从服务器上执行stop slave，reset master命令，重置成主数据库
mysql>stop slave;
Query OK,0 affected (0.00 sec)
mysql>reset master;
Query OK,0 affected (0.00 sec)
Query OK,0 affected (0.00 sec)
mysql>reset master;
Query OK,0 affected (0.00 sec)
3、删除新的主服务器数据库目录中的master.info和relay-log.info文件，否则下次重启时还会按照从服务器来启动.
