【问题描述】：
在master停机维护启动服务之后，slave的Slave_IO_Running状态被置为NO
Slave_SQL_Running为Yes，猜测应该是master的锅
继续检查网络，权限等问题之后仍然为不可用
也尝试重新
change master to ...., ...., ....,
master_log_file = 'master-bin.034555',
master_log_pos = 98;
依旧不可用
1603229:42:51 [Note] Slave SQL thread initialized, starting replication in log 'master-bin.034555' at position 98, relay log './mysqld-relay-bin.0000 01' position: 4 1603229:43:01 [Note] Slave I/O thread: connected to master 'repl@*.*.*.*:3306',replication started in log 'master-bin.034555' at position 98 1603229:43:01 [ERROR] Error reading packet from server: Misconfigured master - server id was not set ( server_errno=1236) 1603229:43:01 [ERROR] Got fatal error 1236: 'Misconfigured master - server id was not set' from master when reading data from binary log 1603229:43:01 [Note] Slave I/O thread exiting, read up to log 'master-bin.034555', position 98 1603229:43:07 [Note] Error reading relay log event: slave SQL thread was killed
检查配置文件发现#server-id = xxx 被注释
【解决方案】：
由于server_id为“Dynamic Variable”
故到master中手动执行
mysql> SETGLOBALserver_id=3028;
Query OK, 0 rows affected (0.00 sec)
最后在将配置文件中添加
server-id=3028
在slave上检查：
mysql>SHOW SLAVE STATUS\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.30.28
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: master-bin.034556
Read_Master_Log_Pos: 59312658
Relay_Log_File: mysqld-relay-bin.000002
Relay_Log_Pos: 64698308
Relay_Master_Log_File: master-bin.034555
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
………………………… Seconds_Behind_Master: 10071
1 row in set (0.00 sec)
解决。
同样，某些时候在start slave时报错“The server is not configured as slave”，
同样也很有可能是server-id的缘故，只需要手动在主和从库上执行：
SET GLOBAL server_id = xxx，并保证两台server-id不一样即可，最后写入my.cnf中。
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