mysql主从同步的原理：
1、在master上开启bin-log日志功能，记录更新、插入、删除的语句。
2、必须开启三个线程，主上开启io线程，从上开启io线程和sql线程。
3、从上io线程去连接master，master通过io线程检查有slave过来的请求，请求日志、postsion位置。
4、master将这些相应的日志返回给slave，slave自己去下载到本地的realy_log里面，写入一个master-info日志记录同步的点。
5、slave的sql线程检查到realy-log日志有更新，然后在本地去exec执行。
一：
Slave I/O: error connecting to master 'backup@192.168.1.x:3306' - retry-time: 60 retries: 86400, Error_code: 1045
解决方法
从服务器上删除掉所有的二进制日志文件，包括一个数据目录下的master.info文件和hostname-relay-bin开头的文件。
master.info:：记录了Mysql主服务器上的日志文件和记录位置、连接的密码。
或者是防火墙问题
二：出现错误提示
Error reading packet from server: File '/home/mysql/mysqlLog/log.000001' not found (Errcode: 2) ( server_errno=29)
解决方法：
由于主服务器运行了一段时间，产生了二进制文件，而slave是从log.000001开始读取的，删除主机二进制文件，包括log.index文件。
三：错误提示如下
Slave SQL: Error 'Table 'xxxx' doesn't exist' on query. Default database: 't591'. Query: 'INSERT INTO `xxxx`(type,post_id,browsenum)
SELECT type,post_id,browsenum FROM xxxx WHERE hitdate='20090209'', Error_code: 1146
解决方法：
由于slave没有此table表，添加这个表，使用slave start 就可以继续同步。
四：错误提示如下
Error 'Duplicate entry '1' for key 1' on query. Default database: 'movivi1'. Query: 'INSERT INTO `v1vid0_user_samename`
VALUES(null,1,'123','11','4545','123')'
Error 'You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax
to use near ' ' at line 1' on query. Default database: 'club'. Query: 'INSERT INTO club.point_process ( GIVEID, GETID, POINT, CREATETIME, DEMO )
VALUES ( 0, 4971112, 5, '2010-12-19 16:29:28', '
1 row in set (0.00 sec)
Mysql > Slave statusG;
显示：Slave_SQL_Running 为 NO
解决方法：
Mysql > stop slave;
Mysql > set global sql_slave_skip_counter =1 ;
Mysql > start slave;
五：错误提示如下
show slave statusG;
Master_Log_File: mysql-bin.000029
Read_Master_Log_Pos: 3154083
Relay_Log_File: c7-relay-bin.000178
Relay_Log_Pos: 633
Relay_Master_Log_File: mysql-bin.000025
Slave_IO_Running: Yes
Slave_SQL_Running: No
Replicate_Do_DB: club
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 1594
Last_Error: Relay log read failure: Could not parse relay log event entry. The possible reasons are:
the master's binary log is corrupted (you can check this by running 'mysqlbinlog' on the binary log),
the slave's relay log is corrupted (you can check this by running 'mysqlbinlog' on the relay log),
a network problem, or a bug in the master's or slave's MySQL code. If you want to check the master's
binary log or slave's relay log, you will be able to know their names by issuing 'SHOW SLAVE STATUS' on this slave.
Skip_Counter: 0
Exec_Master_Log_Pos: 1010663436
这个问题原因是，主数据库突然停止或问题终止，更改了mysql-bin.xxx日志，slave服务器找不到这个文件，需要找到同步的点和日志文件，然后chage master即可。
解决方法：
change master to
master_host='IP',
master_user='同步帐号',
master_password='同步密码',
master_port=3306,
master_log_file='mysql-bin.000025',
master_log_pos=1010663436;
六：错误提示如下
Error 'Unknown column 'qdir' in 'field list'' on query. Default database: 'club'. Query: 'insert into club.question_del (id, pid,
ques_name, givepoint, title, subject, subject_pid, createtime, approve, did, status, intime, order_d, endtime,banzhu_uid,
banzhu_uname,del_cause,qdir) select id, pid, ques_name, givepoint, title, subject, subject_pid, createtime, approve, did,
status, intime, order_d, endtime,'1521859','admin0523','无意义回复',qdir from club.question where id=7330212'
1 row in set (0.00 sec)
这个错误就说club.question_del 表里面没有qdir这个字段 造成的加上就可以了~！
在主的mysql ： 里面查询 Desc club.question_del；
在 错误的从服务器上执行 ： alter table question_del add qdir varchar(30) not null;
七:错误提示如下
Slave_IO_Running: NO
这个错误就是IO 进程没连接上 ，想办法连接上把 把与主的POS 号和文件一定要对，然后重新加载下数据。具体步骤：
slave stop;
change master to master_host='IP地址',master_user='club',master_password='mima ',master_log_file='mysqld-bin.000048',MASTER_LOG_POS=396549485;
注：master_log_file='mysqld-bin.000048',MASTER_LOG_POS=396549485;是从主的上面查出 来的 ：show master statusG;
LOAD DATA FROM MASTER;
load data from master；
slave start;
八 ,mysql报错如下：
mysql> show slave statusG;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.0.198
Master_User: rootclub
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000061
Read_Master_Log_Pos: 494107148
Relay_Log_File: xyxyclub-relay-bin.006609
Relay_Log_Pos: 1073365
Relay_Master_Log_File: mysql-bin.000061
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB: club
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: 494107148
Relay_Log_Space: 1073365
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
1 row in set (0.00 sec)
ERROR:
No query specified #这里提示有错误，刚开始我以为数据库的问题呢，经过查询验证，发现并不是数据库的问题，而是我们操作的问题，
看下面操作。就没有报错误吧。
mysql> mysql> show slave statusG
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: 192.168.0.198
Master_User: rootclub
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000061
Read_Master_Log_Pos: 494248077
Relay_Log_File: xyxyclub-relay-bin.006609
Relay_Log_Pos: 1213077
Relay_Master_Log_File: mysql-bin.000061
Slave_IO_Running: No
Slave_SQL_Running: No
Replicate_Do_DB: club
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: 494246860
Relay_Log_Space: 1214294
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: NULL
1 row in set (0.00 sec)
mysql>
解释：
show slave statusG
G就是结束 再加一个";" 就多余了，所以才报错，这2个结束符号别重复使用就是...
九．mysql> show slave statusG
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: 192.168.1.18
Master_User: tongbu
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000022
Read_Master_Log_Pos: 106
Relay_Log_File: mysqld-relay-bin.000035
Relay_Log_Pos: 251
Relay_Master_Log_File: mysql-bin.000022
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: 1
Exec_Master_Log_Pos: 106
Relay_Log_Space: 552
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: NULL
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 1236
Last_IO_Error: Got fatal error 1236 from master when reading data from binary log: 'Could not find first log file name in binary log index file'
Last_SQL_Errno: 0
Last_SQL_Error:
1 row in set (0.00 sec)
解决方法是在master端从新看一下master状态
在master那边，执行：
flush logs;
show master status;
记下File, Position。
在slave端，执行：
Slave stop
CHANGE MASTER TO MASTER_LOG_FILE='testdbbinlog.000008',MASTER_LOG_POS=107;
slave start;
show slave status G
一切正常。