MySQL的主从备份，主要用于确保数据安全，避免一台机器硬盘损坏导致数据永久丢失；本篇文档实现一主一备。
根据上一篇文档安装两个mysql数据库，分别是192.168.209.128:3306和192.168.209.129:3306；

一、主库(Master)配置

128的机器为主库：
配置主库的my.cnf ,
vim /etc/my.cnf 中增加以下两条内容

##启用二进制日志
log-bin=master_log
##服务器唯一ID，一般取IP最后一段
server-id=128

重启数据库：
service mysqld restart

进入数据库内部 ,创建从库访问主库时的用户backup及密码123456,192.168.209.129为从库的地址，有几个从库就配置几条

mysql> grant all privileges on *.* to 'backup'@'192.168.209.129' identified by '123456' with grant option;
mysql> flush privileges;

查看用户及查看master状态

mysql> use mysql;
mysql> select host, user from user;
mysql> show master status;
+-------------------+----------+--------------+------------------+-------------------+
| File              | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+-------------------+----------+--------------+------------------+-------------------+
| master_log.000006 |     1185 |              |                  |                   |
+-------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
#记住你自己的master_log.000006和1185的值

主库配置完成。

二、从库(Slave)配置

配置从库的my.cnf ,
vim /etc/my.cnf 中增加以下一条内容

server-id=129

重启数据库：
service mysqld restart

进入数据库内部 ,

mysql> stop slave;  #停止slave

mysql> change master to master_host='192.168.209.128', master_user='backup', master_password='123456', master_log_file='master_log.000006';

mysql> start slave;

mysql> show slave status\G;

*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.209.128
                  Master_User: backup
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: master_log.000006
          Read_Master_Log_Pos: 1185
               Relay_Log_File: localhost-relay-bin.000015
                Relay_Log_Pos: 1400
        Relay_Master_Log_File: master_log.000006
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          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: 1185
              Relay_Log_Space: 1778
              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: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 128
                  Master_UUID: ffcca6d0-adb3-11e8-9d65-000c29a44819
             Master_Info_File: /usr/local/mysql/data/master.info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version: 
1 row in set (0.00 sec)

ERROR: 
No query specified

配置完成 可以在主库中创建database、table、及库表的数据，可以查看从库也会相应的操作，说明配置成功。使用中和原来一样在程序中连接主库就可以。

三、常见问题

show slave status\G; 出现下面错误
Last_IO_Error: Got fatal error 1236 from master when reading data from binary log: 'Client requested master to start replication from position > file size'

1. 在主库的安装bin目录下,

./mysqlbinlog  /usr/local/mysql/data/master_log.000002 > yoon.log
// 如果报错：mysqlbinlog: [ERROR] unknown variable 'default-character-set=utf8mb4'； 则执行：
./mysqlbinlog  --no-defaults /usr/local/mysql/data/master_log.000002 > yoon.log
tail  -f  yoon.log
//查看 end_log_pos 154,的数值

2. 在从库的>MySQL 中

mysql> stop slave;
change master  to master_host='192.168.209.128',master_port=3306,master_user='backup',master_password='123456',master_log_file='master_log.000002',master_log_pos=154;
mysql> start slave;
mysql> show slave status\G;