MySQL主從同步：
有三臺mysql A B C
其中A 和 B 已經做了主從，又把B做成了C的主，然後問題是，B上說什麼也不記錄bin-log，所以C就一直不能從B上同步到數據，B能從A上順利同步到數據。
解決辦法：
在B的配置文件my.cnf 加上一句
log-slave-updates
AB主從已設置好，問題出在BC之間
B上：
mysql>grant replication slave on *.* to 'repl2'@'192.168.1.118' identified by 'mysqlslave'mysql> flush table with read clock;mysql> show master status; +-----------------+----------+--------------+------------------+| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | +-----------------+----------+--------------+------------------+| B_Master.000002 | 524565 | db1,db2 | mysql,db1 | +-----------------+----------+--------------+------------------+1 row in set (0.00 sec)123456789123456789
C上：
vim /usr/local/mysql_slave/my.cnf 修改如下： server-id = 2 //區別於主的id相同在主上已經配置過，註釋下面的配置#指定要同步的庫 #replicate-do-db=db2 #忽略不同步的庫#replicate-ignore-db=mysql1234567812345678
重啓生效：/etc/init.d/mysqldslave restart
mysql> change master to master_host='192.168.1.119',master_port=3307,master_user='repl2',master_password='mysqlslave',master_log_file='B_Master.000002',master_log_pos=524565;11
C連接B時報錯：
這樣配置了之後，B能同步A，但是C連接不到B，提示：
Last_IO_Error: error connecting to master '[email protected]:3307' - retry-time: 60 retries: 8640011
查看C錯誤日誌：
Version: '5.1.73' socket: '/tmp/mysql.sock' port: 3306 MySQL Community Server (GPL)160512 8:40:29 [ERROR] Slave I/O: error connecting to master '[email protected]:3307' - retry-time: 60 retries: 86400, Error_code: 1130160512 8:40:53 [Note] Error reading relay log event: slave SQL thread was killed160512 8:40:53 [Note] Slave I/O thread killed while connecting to master160512 8:40:53 [Note] Slave I/O thread exiting, read up to log 'B_Master.000003', position 340160512 8:42:14 [Note] 'CHANGE MASTER TO executed'. Previous state master_host='192.168.1.119', master_port='3307', master_log_file='B_Master.000003', master_log_pos='340'. New state master_host='192.168.1.119', master_port='3307', master_log_file='B_Master.000004', master_log_pos='338'.160512 8:42:29 [Note] Slave SQL thread initialized, starting replication in log 'B_Master.000004' at position 338, relay log './localCoohx-relay-bin.000001' position: 4160512 8:42:29 [ERROR] Slave I/O: error connecting to master '[email protected]:3307' - retry-time: 60 retries: 86400, Error_code: 1130160512 8:48:09 [Note] /usr/local/mysql/bin/mysqld: Normal shutdown123456789101112123456789101112
C連接不到B，再試着直接C登錄B：
[root@localCoohx ~]# mysql -u repl2 -h192.168.1.119 -P 3307 -pmysqlslaveERROR 1130 (HY000): Host '192.168.1.118' is not allowed to connect to this MySQL server1212
問題就出在這了，突然想起來B沒有給C授權遠程登錄，於是在B上：
mysql> grant all on *.* to 'repl2'@'192.168.1.118' identified by 'mysqlslave'; Query OK, 0 rows affected (0.01 sec) mysql> flush privileges; Query OK, 0 rows affected (0.00 sec)12341234
之後就連接成功了。
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由於之前mysql 從機的IP發生變化，所以需要BC之間從新設置主從：
B 192.168.1.112 C:192.168.1.118
B上： 重新給作爲Slave的C授權
mysql> grant replication slave on *.* to 'repl2'@192.168.1.118 identified by 'mysqlslave'; Query OK, 0 rows affected (0.00 sec) mysql> flush privileges; mysql> flush tables with read lock; //讓事務show master status鎖死表的讀mysql> show master status; +--------------+----------+--------------+------------------+| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | +--------------+----------+--------------+------------------+| coohx.000002 | 333 | db1 | mysql | +--------------+----------+--------------+------------------+1 row in set (0.00 sec)12345678910111234567891011
C上：
mysql> slave stop; Query OK, 0 rows affected, 1 warning (0.00 sec) mysql> change master to master_host='192.168.1.112',master_port=3307,master_user='repl2',master_password='mysqlslave',master_log_file='B_Master.000028',master_log_pos=106;ERROR 1201 (HY000): Could not initialize master info structure; more error messages can be found in the MySQL error log C上重新設置主信息失敗. 查看錯誤日誌： 160529 13:15:52 [Note] /usr/local/mysql/bin/mysqld: ready for connections. Version: '5.1.73' socket: '/tmp/mysql.sock' port: 3306 MySQL Community Server (GPL)160529 13:40:50 [ERROR] Failed to open the relay log './localCoohx-relay-bin.000004' (relay_log_pos 549)160529 13:40:50 [ERROR] Could not find target log during relay log initialization160529 13:45:38 [ERROR] Failed to open the relay log './localCoohx-relay-bin.000004' (relay_log_pos 549)160529 13:45:38 [ERROR] Could not find target log during relay log initialization160529 13:52:06 [ERROR] Failed to open the relay log './localCoohx-relay-bin.000004' (relay_log_pos 549)160529 13:52:06 [ERROR] Could not find target log during relay log initialization160529 13:52:18 [ERROR] Failed to open the relay log './localCoohx-relay-bin.000004' (relay_log_pos 549)160529 13:52:18 [ERROR] Could not find target log during relay log initialization160529 14:00:21 [ERROR] Failed to open the relay log './localCoohx-relay-bin.000004' (relay_log_pos 549)160529 14:00:21 [ERROR] Could not find target log during relay log initialization123456789101112131415161718192021222324123456789101112131415161718192021222324
localCoohx-relay-bin.000004 這是上一次C同步B後生成的relay重演文件，後來由於改過主機名，所以作廢，於是刪掉這些同步文件，繼續執行：
mysql> change master to master_host='192.168.1.112',master_port=3307,master_user='repl2',master_password='mysqlslave',master_log_file='B_Master.000028',master_log_pos=106; ERROR 1201 (HY000): Could not initialize master info structure; more error messages can be found in the MySQL error log1212
還是出錯，查看slave狀態：
mysql> show slave status\G;*************************** 1. row *************************** Slave_IO_State: Master_Host: 192.168.1.119 Master_User: repl2 Master_Port: 3307 Connect_Retry: 60 Master_Log_File: B_Master.000005 Read_Master_Log_Pos: 405 Relay_Log_File: localCoohx-relay-bin.000004 Relay_Log_Pos: 549 Relay_Master_Log_File: B_Master.000005 Slave_IO_Running: No Slave_SQL_Running: No 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: 405 Relay_Log_Space: 0 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: NULLMaster_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error:1 row in set (0.00 sec)12345678910111213141516171819202122232425262728293031323334353637383940411234567891011121314151617181920212223242526272829303132333435363738394041
顯示爲上一次主從同步時主的信息，主B的IP已經改變，所以重新設置slave-C，但是失敗，
解決辦法：
mysql> slave stop; Query OK, 0 rows affected, 1 warning (0.00 sec) mysql> reset slave; //這是關鍵一步！！！Query OK, 0 rows affected (0.03 sec)1234512345
mysql> change master to master_host='192.168.1.112',master_port=3307,master_user='repl2',master_password='mysqlslave',master_log_file='B_Master.000028',master_log_pos=106; Query OK, 0 rows affected (0.09 sec) mysql> slave start; Query OK, 0 rows affected (0.05 sec)12341234
mysql> show slave status\G;*************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.1.112 Master_User: repl2 Master_Port: 3307 Connect_Retry: 60 Master_Log_File: B_Master.000028 Read_Master_Log_Pos: 106 Relay_Log_File: Coohx_slave-relay-bin.000002 Relay_Log_Pos: 250 Relay_Master_Log_File: B_Master.000028 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: 106 Relay_Log_Space: 411 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: 0Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error:1 row in set (0.00 sec)12345678910111213141516171819202122232425262728293031323334353637383940411234567891011121314151617181920212223242526272829303132333435363738394041
成功連接到主，進行同步。
補充：
查看某一賬戶權限
mysql> show grants for ‘repl2’@’192.168.1.119’;
+——————————————————————————————————————————+
| Grants for [email protected] |
+——————————————————————————————————————————+
| GRANT REPLICATION SLAVE ON . TO ‘repl2’@’192.168.1.119’ IDENTIFIED BY PASSWORD ‘*EBB378AC232302FF0D4565FFF9F42577B1C04625’ |
+——————————————————————————————————————————+
1 row in set (0.00 sec)
總結：在同一臺mysql服務器上第二次設置從服務器時，應先關掉上一次的主從連接，reset清空以前的master信息，然後重新設置新的slave。
即：
stop reset change master123123