Master-Master互为主备
1：按照主从配置步骤将MasterB配置成MasterA的从库；
参考我这篇文章：
2：确保MasterB没有写入，通过show master status命令在MasterB上得到其同步点，再将MasterA配置成MasterB的从库。
通常，为了简化逻辑，其中一个Master会设置为只读，正常只通过另外一个Master进行读写。 若要两边都写，为了避免自增id冲突，一般会设置奇偶错开，即一台的自增ID均为奇数，另一台均为偶数。
这里假设你已经按照我第一篇文章做了主从。
配置实例：
1：在Master B（Slave）的配置文件中添加
port = 3307log_bin = /var/lib/mysql/mysql-binlog binlog_do_db = testSM
2：在MasterA（Master）的配置文件中添加
prot=3306 master-host = 10.4.5.9master-user = gechong1master-password = gechong1master-port = 3307master-connect-retry = 5replicate-do-db = testSM
3：在Master B（Slave）上创建复制账号gechong1
GRANT REPLICATION SLAVE ON *.* TO gechong1@'%' IDENTIFIED BY 'gechong1';
4：两边都重启服务登陆数据库
在Master A（Master）上查看
mysql> show master status;+---------------------+----------+--------------+------------------+| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |+---------------------+----------+--------------+------------------+| mysql-binlog.000002 | 106 | test | |+---------------------+----------+--------------+------------------+1 row in set (0.00 sec)mysql> show slave status \G*************************** 1. row *************************** Slave_IO_State: Connecting to master Master_Host: 10.4.5.9 Master_User: gechong1 Master_Port: 3306 Connect_Retry: 5 Master_Log_File: Read_Master_Log_Pos: 4 Relay_Log_File: mysqld-relay-bin.000001 Relay_Log_Pos: 4 Relay_Master_Log_File: Slave_IO_Running: No Slave_SQL_Running: Yes Replicate_Do_DB: test Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 0 Relay_Log_Space: 106 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: NULLMaster_SSL_Verify_Server_Cert: No Last_IO_Errno: 2013 Last_IO_Error: error connecting to master 'gechong1@10.4.5.9:3306' - retry-time: 5 retries: 86400 Last_SQL_Errno: 0 Last_SQL_Error: 1 row in set (0.00 sec)
在MasterB（Slave）上查看
mysql> show slave status \G*************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 10.4.14.168 Master_User: gechong Master_Port: 3306 Connect_Retry: 5 Master_Log_File: mysql-binlog.000002 Read_Master_Log_Pos: 106 Relay_Log_File: mysqld-relay-bin.000006 Relay_Log_Pos: 254 Relay_Master_Log_File: mysql-binlog.000002 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: test Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 106 Relay_Log_Space: 558 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: 1 row in set (0.00 sec)mysql> show master status;+---------------------+----------+--------------+------------------+| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |+---------------------+----------+--------------+------------------+| mysql-binlog.000001 | 327 | | |+---------------------+----------+--------------+------------------+1 row in set (0.00 sec)
可以看到 Master A：Slave_IO_Running: No
可以参照第一篇文档，重新配置参数即可。