bitscn.com 把步骤写下来，至于会出现的什么问题，以后随时更新。这里我同步的php?name=%e6%95%b0%e6%8d%ae%e5%ba%93>数据库是test
1、环境描述。
主机：192.168.0.167（a）
主机：192.168.0.251（b）
mysql 版本为5.1.11
2、授权用户。
a：
mysql> grant replication slave,file on *.* to backup_251@192.168.0.251 identified
by 123456;
query ok, 0 rows affected (0.00 sec)
mysql> flush privileges;
query ok, 0 rows affected (0.00 sec)
b：
mysql> grant replication slave,file on *.* to backup_167@192.168.0.167 identified
by 123456;
query ok, 0 rows affected (0.00 sec)
mysql> flush privileges;
query ok, 0 rows affected (0.00 sec)
然后都停止mysql 服务器。
3、配置文件。
在两个机器上的my.cnf里面都开启二进制日志 。
a：
user = mysql
log-bin=mysql-bin
server-id = 1
binlog-do-db=test
binlog-ignore-db=mysql
replicate-do-db=test
replicate-ignore-db=mysql
log-slave-updates
slave-skip-errors=all
sync_binlog=1
auto_increment_increment=2
auto_increment_offset=1
b：
user = mysql
log-bin=mysql-bin
server-id = 2
binlog-do-db=test
binlog-ignore-db=mysql
replicate-do-db=test
replicate-ignore-db=mysql
log-slave-updates
slave-skip-errors=all
sync_binlog=1
auto_increment_increment=2
auto_increment_offset=2
至于这些参数的说明具体看手册。
红色的部分非常重要，如果一个master 挂掉的话，另外一个马上接管。
紫红色的部分指的是服务器频繁的刷新日志。这个保证了在其中一台挂掉的话，日志刷新到另外一台。从而保证了数据的同步 。
4、重新启动mysql服务器。
在a和b上执行相同的步骤
[root@localhost ~]# /usr/local/mysql/bin/mysqld_safe &
[1] 4264
[root@localhost ~]# 071213 14:53:20 mysqld_safe logging to /usr/local/mysql/data/localhost.localdomain.err.
/usr/local/mysql/bin/mysqld_safe: line 366: [: -eq: unary operator expected
071213 14:53:20 mysqld_safe starting mysqld daemon with databases from /usr/local/mysql/data
5、进入mysql的shell。
a：
mysql> flush tables with read lockg
query ok, 0 rows affected (0.00 sec)
mysql> show master statusg
*************************** 1. row ***************************
file: mysql-bin.000007
position: 528
binlog_do_db: test
binlog_ignore_db: mysql
1 row in set (0.00 sec)
b：
mysql> flush tables with read lock;
query ok, 0 rows affected (0.00 sec)
mysql> show master statusg
*************************** 1. row ***************************
file: mysql-bin.000004
position: 595
binlog_do_db: test
binlog_ignore_db: mysql
1 row in set (0.00 sec)
然后备份自己的数据，保持两个机器的数据一致。
方法很多。完了后看下一步。
6、在各自机器上执行change master to命令。
a：
mysql> change master to
-> master_host=192.168.0.251,
-> master_user=backup_251,
-> master_password=123456,
-> master_log_file=mysql-bin.000004,
-> master_log_pos=595;
query ok, 0 rows affected (0.01 sec)
mysql> start slave;
query ok, 0 rows affected (0.00 sec)
b：
mysql> change master to
-> master_host=192.168.0.167,
-> master_user=backup_167,
-> master_password=123456,
-> master_log_file=mysql-bin.000007,
-> master_log_pos=528;
query ok, 0 rows affected (0.01 sec)
mysql> start slave;
query ok, 0 rows affected (0.00 sec)
7、查看各自机器上的io进程和 slave进程是否都开启。
a：
mysql> show processlistg
*************************** 1. row ***************************
id: 2
user: repl
host: 192.168.0.251:54475
db: null
command: binlog dump
time: 1590
state: has sent all binlog to slave; waiting for binlog to be updated
info: null
*************************** 2. row ***************************
id: 3
user: system user
host:
db: null
command: connect
time: 1350
state: waiting for master to send event
info: null
*************************** 3. row ***************************
id: 4
user: system user
host:
db: null
command: connect
time: 1149
state: has read all relay log; waiting for the slave i/o thread to update it
info: null
*************************** 4. row ***************************
id: 5
user: root
host: localhost
db: test
command: query
time: 0
state: null
info: show processlist
4 rows in set (0.00 sec)
b：
mysql> show processlistg
*************************** 1. row ***************************
id: 1
user: system user
host:
db: null
command: connect
time: 2130
state: waiting for master to send event
info: null
*************************** 2. row ***************************
id: 2
user: system user
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