====== mysql主从同步 ======
===== 环境 =====
主库：121.43.104.34 mysql版本 [5.5.43-0ubuntu0.14.04.1-log]

从库：121.40.171.96 mysql版本 [5.7.18-0ubuntu0.16.04.1-log]
===== 主库配置 =====
修改/etc/mysql/my.cnf在[mysqld]下配置
<code>
#[必须]启用二进制日志
log-bin                 = mysql-bin
#[必须]服务器唯一ID，默认是1，一般取IP最后一段
server-id               = 34
</code>

保存后重启mysql:
<code>sudo /etc/init.d/mysql restart</code>

登录mysql
<code>mysql -uroot -p</code>

创建用户syn并授权给从服务器:
<code>grant replication slave on *.* to 'syn'@'121.40.171.96' identified by 'syn';</code>

刷新权限:
<code>flush privileges;</code>

主库状态
<code>show master status;</code>
<code>
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000003 |    17384 |              |                  |
+------------------+----------+--------------+------------------+
</code>
===== 配置从库 =====
修改/etc/mysql/mysql.conf.d/mysqld.cnf在[mysqld]下配置
<code>
#[不是必须]启用二进制日志
log-bin                 = mysql-bin
#[必须]服务器唯一ID，默认是1，一般取IP最后一段
server-id               = 96
</code>

保存后重启mysql:
<code>sudo /etc/init.d/mysql restart</code>

登录mysql
<code>mysql -uroot -p</code>

执行
<code>
change master to master_host = '121.43.104.34', master_user = 'syn', master_port=3306, master_password='syn', master_log_file = 'mysql-bin.000003', master_log_pos=17384;
</code>

开启复制
<code>start slave;</code>

查看从库状态
<code>show slave status\G;</code>
<code>
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 121.43.104.34
                  Master_User: syn
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 20073
               Relay_Log_File: iZbp12rdwfbgblafgipsh5Z-relay-bin.000002
                Relay_Log_Pos: 2985
        Relay_Master_Log_File: mysql-bin.000003
             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: 20073
              Relay_Log_Space: 3202
              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: 34
                  Master_UUID: 
             Master_Info_File: /var/lib/mysql/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
</code>
到这里，主从就算配置完了，在主库create database test;，从库就马上看到新建的数据库。
===== 数据库迁移 =====
有个问题，如果主库已经存在的一个数据库，在里面做修改，同步到从库会报错，类似：不存在该库表XXXXX

这时候就得按以下方法，先把主库整个导出再导入到从库，然后开始同步就不会报错。

备份数据库，输入密码
<code>mysqldump -u root -p record_app>/mnt/lost+found/backup/mysql/record_app_`date +%Y%m%d`.sql</code>
拷贝备份的sql文件到从库机器
<code>scp /mnt/lost+found/backup/mysql/record_app_20170526.sql gxx@121.40.171.96:/home/gxx/</code>
主库状态
<code>show master status;</code>
<code>
+------------------+----------+--------------+------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000003 |    17385 |              |                  |
+------------------+----------+--------------+------------------+
</code>
登陆从库，停止复制
<code>stop slave;</code>
创建数据库
<code>create database record_app;</code>
使用数据库
<code>use record_app;</code>
导入数据库
<code>source /home/gxx/record_app_20170526.sql</code>
执行
<code>
change master to master_host = '121.43.104.34', master_user = 'syn', master_port=3306, master_password='syn', master_log_file = 'mysql-bin.000003', master_log_pos=17385;
</code>
开启同步
<code>start slave;</code>