之前为主从配置，后来分割成2个单实例。
现在环境需要，重新配置为主从，之前参数都已配置好，直接启动，如下：

mysql> change master to master_host='192.168.12.193',master_port=3306,master_user='master',master_password='123456',master_log_file='master-bin.000569',master_log_pos=107;
ERROR 29 (HY000): File './slave-relay-bin.000494' not found (Errcode: 2)

mysql>reset slave;      也不行

查看报错日志：
131210 10:56:44 [ERROR] Failed to open the relay log './slave-relay-bin.000494' (relay_log_pos 591818895)
131210 10:56:44 [ERROR] Could not find target log during relay log initialization
131210 10:56:44 [ERROR] Failed to initialize the master info structure

[root@b28-12195 data]# rm -rf master.info relay-log.info slave-relay-bin.*

mysql> change master to master_host='192.168.12.193',master_port=3306,master_user='master',master_password='123456',master_log_file='master-bin.000569',master_log_pos=107;
Query OK, 0 rows affected (0.00 sec)

mysql> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 192.168.12.193
                  Master_User: master
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: master-bin.000572
          Read_Master_Log_Pos: 107
               Relay_Log_File: slave-relay-bin.000002
                Relay_Log_Pos: 254
        Relay_Master_Log_File: master-bin.000572
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: test
           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: 107
              Relay_Log_Space: 410
              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: 1
1 row in set (0.00 sec)