ERROR 3021 (HY000): This operation cannot be performed with a running slave io thread; run STOP SLAVE IO_THREAD FOR CHANNEL '' first.

mysql 主从服务，停止从服务器从机器上执行开始复制命令出现错误

解决故障

io线程开启中无法对从服务器进行修改，因此我们需要关闭io线程

mysql> STOP SLAVE IO_THREAD;
Query OK, 0 rows affected (0.00 sec)
mysql> change master to master_host='192.168.0.99',master_port=3307,master_user='copy',master_password='copy',master_log_file='mysql-bin.000001',master_log_pos=154;
Query OK, 0 rows affected, 2 warnings (0.00 sec)
mysql> START SLAVE IO_THREAD;
Query OK, 0 rows affected (0.00 sec)