一.主从的作用：
1.可以当做一种备份方式
2.用来实现读写分离，缓解一个数据库的压力
二.MySQL主从备份原理
master 上提供binlog ,
slave 通过 I/O线程从 master拿取 binlog,并复制到slave的中继日志中
slave 通过 SQL线程从 slave的中继日志中读取binlog ,然后解析到slave中
部署主从环境：主服务器：192.168.1.110（编译好的MySQL5.1版本的数据库）
从服务器：192.168.1.120（编译好的MySQL5.1版本的数据库）
（温馨提示：主和从数据库版本必须是一样。或者主库的数据库版本必须比从库高,不然会导致很多故障的发生。）
三：生产环境应用MySQL主从同步场景：
1. 一般用主库做为提供业务用户写操作（比如：在互联网上写一条微博，这时候就会写到mysql数据库的主库中）
2. 一般用从库做为提供业务用户读操作（比如：在互联网上，我想看一条微博，这时候里面提供数据就是MySQL数据库的从库中。）
(1)在主服务器（192.168.1.110）上操作。
[root@Andy ~]# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:0C:29:5E:6F:A7
inet addr:192.168.1.110 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe5e:6fa7/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:141354 errors:0 dropped:0 overruns:0 frame:0
TX packets:140807 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:142083379 (135.5 MiB) TX bytes:17815696 (16.9 MiB)
Interrupt:193 Base address:0x2000
[root@Andy ~]# vi /etc/my.cnf
[mysqld]在mysqld下添加以上两行。
server-id = 1
log-bin= Andy -bin
[root@Andy ~]# /etc/init.d/mysqld restart
Shutting down MySQL[ OK ]
Starting MySQL.[ OK ]
[root@Andy ~]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.1.44 Source distribution
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> show master status;
+--------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+--------------------+----------+--------------+------------------+
| Andy-bin.000001 | 106 | | |
+--------------------+----------+--------------+------------------+
1 row in set (0.00 sec)
请记住：File里的Andy-bin.000001 和 Position 106 。
Mysql> grant replication slave on *.* to 'python'@'192.168.1.%' identified by '123456';
mysql> quit
Bye
在从服务器（192.168.1.120）上操作：
[root@Andy ~]# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:0C:29:2B:8E:D2
inet addr:192.168.1.120 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe2b:8ed2/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:180290 errors:0 dropped:0 overruns:0 frame:0
TX packets:146169 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:223411069 (213.0 MiB) TX bytes:15504427 (14.7 MiB)
Interrupt:193 Base address:0x2000
[root@Andy ~]# vi /etc/my.cnf
把server-id = 1 改为：server-id = 2
然后重启Mysql服务：[root@Andy ~]# /etc/init.d/mysqld restart
Shutting down MySQL........[ OK ]
Starting MySQL.[ OK ]
[root@Andy ~]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.1.44 Source distribution
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> CHANGE MASTER TO MASTER_HOST='192.168.1.110', MASTER_PORT=3306, MASTER_USER='python', MASTER_PASSWORD='123456', MASTER_LOG_FILE=' Andy-bin .000001', MASTER_LOG_POS=106;
mysql> start slave;
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: 192.168.1.110
Master_User: python
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: Andy-bin.000001
Read_Master_Log_Pos: 106
Relay_Log_File: Andy-relay-bin.000002
Relay_Log_Pos: 253
Relay_Master_Log_File: Andy-bin.000001
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: 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:
1 row in set (0.01 sec)
如果： Slave_IO_Running: Yes （主从I/O正确）
Slave_SQL_Running: Yes（主从进程正确）