**************************前言**************************
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.环境：
OS CentOS5.5
DB MySQL5.5.3-m3
安装 CentOS5.5 请看
安装 MySQL5.5.3-m3 请看
三.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
四.主从复制大前提
需要master与slave同步，因为笔者的数据库数据量不大，所以无需考虑太多，直接把
master上的data复制到了slave上，但是如果是大的数据量，比如像taobao这个的系统
那么数据同步也是很难得，需要有一个完善的方案，有兴趣的可以看看这篇文章
%E5%A2%9E%E9%87%8F%E6%97%A5%E5%BF%97%E8%BF%AD%E4%BB%A3%E5%90%8C%E6%AD%A5%E5%92%8C%E9%98%BF%E5%9F%BA%E9%87%8C%E6%96%AF%E6%82%96%E8%AE%BA.html
**************************开始***************************************************
一.将master设置为只读。
mysql> flush tables with read lock;
二.用master中的data文件夹替换slave中的data文件夹
比如 用 tar zcvf mysql_data.gz /media/raid10/mysql/3306/data
然后 mv mysql_data.gz /media/raid10/htdocs/blog/wordpress/
因为我的 /media/raid10/htdocs/blog/wordpress/ 是 Nginx 的主目录
所以可以在 slave上，用wget下载这个文件，然后 解压，并覆盖slave上的data文件
注意：覆盖之前最好备份源文件
三.配置master的my.cnf,添加以下内容
在[mysqld]配置段添加如下字段
server-id=1
log-bin=/media/raid10/mysql/3306/binlog/binlog //这里写你的binlog绝对路径名
binlog-do-db=blog //需要同步的数据库，如果没有本行，，即表示同步所有的数据库
binlog-ignore-db=mysql //被忽略的数据库
这里给出我的my.cnf配置文件
[client]
character-set-server = utf8
port = 3306
socket = /tmp/mysql.sock
[mysqld]
character-set-server = utf8
replicate-ignore-db = mysql
replicate-ignore-db = test
replicate-ignore-db = information_schema
user = mysql
port = 3306
socket = /tmp/mysql.sock
basedir = /usr/local/webserver/mysql
datadir = /media/raid10/mysql/3306/data
log-error = /media/raid10/mysql/3306/mysql_error.log
pid-file = /media/raid10/mysql/3306/mysql.pid
open_files_limit = 10240
back_log = 600
max_connections = 5000
max_connect_errors = 6000
table_cache = 614
external-locking = FALSE
max_allowed_packet = 16M
sort_buffer_size = 1M
join_buffer_size = 1M
thread_cache_size = 300
#thread_concurrency = 8
query_cache_size = 20M
query_cache_limit = 2M
query_cache_min_res_unit = 2k
default-storage-engine = MyISAM
thread_stack = 192K
transaction_isolation = READ-COMMITTED
tmp_table_size = 20M
max_heap_table_size = 20M
long_query_time = 3
log-slave-updates
log-bin = /media/raid10/mysql/3306/binlog/binlog
binlog-do-db=blog
binlog-ignore-db=mysql
binlog_cache_size = 4M
binlog_format = MIXED
max_binlog_cache_size = 8M
max_binlog_size = 20M
relay-log-index = /media/raid10/mysql/3306/relaylog/relaylog
relay-log-info-file = /media/raid10/mysql/3306/relaylog/relaylog
relay-log = /media/raid10/mysql/3306/relaylog/relaylog
expire_logs_days = 30
key_buffer_size = 10M
read_buffer_size = 1M
read_rnd_buffer_size = 6M
bulk_insert_buffer_size = 4M
myisam_sort_buffer_size = 8M
myisam_max_sort_file_size = 20M
myisam_repair_threads = 1
myisam_recover
interactive_timeout = 120
wait_timeout = 120
skip-name-resolve
#master-connect-retry = 10
slave-skip-errors = 1032,1062,126,1114,1146,1048,1396
#master-host = 192.168.1.2
#master-user = username
#master-password = password
#master-port = 3306
server-id = 1
innodb_additional_mem_pool_size = 16M
innodb_buffer_pool_size = 20M
innodb_data_file_path = ibdata1:56M:autoextend
innodb_file_io_threads = 4
innodb_thread_concurrency = 8
innodb_flush_log_at_trx_commit = 2
innodb_log_buffer_size = 16M
innodb_log_file_size = 20M
innodb_log_files_in_group = 3
innodb_max_dirty_pages_pct = 90
innodb_lock_wait_timeout = 120
innodb_file_per_table = 0
#log-slow-queries = /media/raid10/mysql/3306/slow.log
#long_query_time = 10
[mysqldump]
quick
max_allowed_packet = 32M
四.在master机上为slave机添加一同步帐号
mysql> grant replication slave on *.* to ‘admin’@’172.29.141.115’ identified by ‘12345678’;
mysql> flush privileges ;