mysql主从搭建：
怎么安装mysql数据库，这里不讲，只说它的主从复制，步骤如下：
1、主从服务器分别作以下操作：
1.1、版本一致
1.2、初始化表，并在后台启动mysql
1.3、修改root的密码
2、修改主服务器master:
#vi /etc/my.cnf
[mysqld]
log-bin=mysql-bin //[必须]启用二进制日志
server-id=1 //[必须]服务器唯一ID
3、修改从服务器slave:
#vi /etc/my.cnf
[mysqld]
log-bin=mysql-bin //[必须]启用二进制日志
server-id=2 //[必须]服务器唯一ID
4、重启两台服务器的mysql
/etc/init.d/mysql restart
5、在主服务器上建立帐户并授权slave:
#/usr/local/mysql/bin/mysql -uroot -p
mysql>GRANT REPLICATION SLAVE ON *.* to 'test'@'%' identified by '123456'; //一般不用root帐号，“%”表示所有客户端都可能连，只要帐号，密码正确，此处可用具体客户端IP代替，如192.168.0.146，加强安全。
6、登录主服务器的mysql，查询master的状态
mysql>show master status;
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000004 | 308 | | |
+------------------+----------+--------------+------------------+
1 row in set (0.00 sec)
注：执行完此步骤后不要再操作主服务器MYSQL，防止主服务器状态值变化
7、配置从服务器Slave：
mysql>change master to master_host='192.168.0.144',master_user='test',master_password='123456',master_log_file='mysql-bin.000004',master_log_pos=308; //注意不要断开，“308”无单引号。
Mysql>start slave; //启动从服务器复制功能
8、检查从服务器复制功能状态：
mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.0.144 //主服务器地址
Master_User: test //授权帐户名，尽量避免使用root
Master_Port: 3306 //数据库端口，部分版本没有此行
Connect_Retry: 60
Master_Log_File: mysql-bin.000004
Read_Master_Log_Pos: 600 //#同步读取二进制日志的位置，大于等于>=Exec_Master_Log_Pos
Relay_Log_File: ddte-relay-bin.000003
Relay_Log_Pos: 251
Relay_Master_Log_File: mysql-bin.000004
Slave_IO_Running: Yes //此状态必须YES
Slave_SQL_Running: Yes //此状态必须YES
......
注：Slave_IO及Slave_SQL进程必须正常运行，即YES状态，否则都是错误的状态(如：其中一个NO均属错误)。
以上操作过程，主从服务器配置完成。
9、主从服务器测试：
主服务器Mysql，建立数据库，并在这个库中建表插入一条数据：
mysql> create database hi_db;
Query OK, 1 row affected (0.00 sec)
mysql> use hi_db;
Database changed
mysql> create table hi_tb(id int(3),name char(10));
Query OK, 0 rows affected (0.00 sec)
mysql> insert into hi_tb values(001,'bobu');
Query OK, 1 row affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| hi_db |
| mysql |
| test |
+--------------------+
4 rows in set (0.00 sec)
从服务器Mysql查询：
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| hi_db | //I'M here，大家看到了吧
| mysql |
| test |
+--------------------+
4 rows in set (0.00 sec)
mysql> use hi_db
Database changed
mysql> select * from hi_tb; //可以看到在主服务器上新增的具体数据
+------+------+
| id | name |
+------+------+
| 1 | bobu |
+------+------+
1 row in set (0.00 sec)
mysql主从故障切换：
首先保证主从数据库都开启二进制日志，方法是在my.cnf中的[mysqld]节中加入log-bin=log-bin-name
然后查看是否开启
MariaDB [(none)]> show variables like 'log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_bin | ON |
+---------------+-------+
1 row in set (0.00 sec)
为了在切换时不会漏掉数据库的更新，必须将主数据库停掉，设为只读：set global read_only=1;
MariaDB [(none)]> set global read_only=1;
Query OK, 0 rows affected (0.00 sec)
show variables; 确认 read_only ON
MariaDB [(none)]> show variables like 'read_only';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| read_only | ON |
+---------------+-------+
1 row in set (0.00 sec)
然后在主库
mysql> flush logs; 刷新一下log-bin,在从库中查看mysql> show slave status \G 是否完全更新
主库：
MariaDB [(none)]> flush logs;
Query OK, 0 rows affected (0.34 sec)
MariaDB [(none)]> show master status;
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000003 | 365 | | |
+------------------+----------+--------------+------------------+
1 row in set (0.00 sec)
从库：
MariaDB [(none)]> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.0.146
Master_User: test
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000003
Read_Master_Log_Pos: 365
Relay_Log_File: jinbi2-relay-bin.000004
Relay_Log_Pos: 652
Relay_Master_Log_File: mysql-bin.000002
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
确认主库和从库的file和pos是一致的。
查看主库的状态mysql> show master status \G 是否还有数据更新，如果没有就可以停掉从库
MariaDB [(none)]> stop slave;
更改从库mysql的身份为master
MariaDB [(none)]> reset master;
Query OK, 0 rows affected (0.16 sec)
MariaDB [(none)]> show master status;
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000001 | 312 | | |
+------------------+----------+--------------+------------------+
1 row in set (0.00 sec)
这时可以关掉新主库的只读属性
mysql> set global read_only=0;
创建一个新的库，一会从库连上后查看是否同步：
MariaDB [(none)]> create database t1;
Query OK, 1 row affected (0.00 sec)
更改主库mysql的身份为slave
MariaDB [(none)]> reset slave;
Query OK, 0 rows affected (0.16 sec)
新从库改变连接的主库信息：
MariaDB [(none)]> change master to master_host='192.168.0.144', master_user='test', master_password='123456', master_log_file='mysql-bin.000001', master_log_pos=312;
Query OK, 0 rows affected (0.16 sec)
查看新从库状态：
MariaDB [(none)]> show slave status\G;
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.0.144
Master_User: test
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000001
Read_Master_Log_Pos: 429
Relay_Log_File: jinbi4-relay-bin.000002
Relay_Log_Pos: 652
Relay_Master_Log_File: mysql-bin.000001
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
查看刚才新主库创建的数据库是否已经同步过来：
MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| bai |
| information_schema |
| mysql |
| performance_schema |
| t1 |
| test |
+--------------------+
主从切换完成！