很多朋友都想在一臺服務器上運行多個MySQL Instance，究竟怎么做呢？
首先要明晰幾個原理， 簡稱為mysqld讀取my.cnf的順序：
第一搜，首先讀取/etc/my.cnf，多實例這個配置文件不會存在。：-（
第二搜，$datadir/my.cnf，在data目錄下尋找此配置文件。
第三搜，defaultfile=/path/my.cnf 通常寫在命令行上，mysqld_safe defaultfile=/tmp/my.cnf &等執行。
第四搜，~/my.cnf 當前用戶下的配置文件。

mysqld多進程運行的必要條件，就是pid文件，datadir，socket，port是獨立分開的。
| Variable_name | Value |
| datadir | /home/mysql/ |
| Variable_name | Value |
| socket | /home/mysql/mysql.sock |
| Variable_name | Value |
| pid_file | /home/mysql/mysql.pid |
| Variable_name | Value |
| port | 3306 |

單一版本實現多實例
#pwd
/usr/local/
#touch my_multi.cnf
#cat my_multi.cnf
[mysqld_multi]
mysqld = /usr/bin/mysqld_safe
mysqladmin = /usr/bin/mysqladmin
user = root

[mysqld1]
socket = /tmp/mysql_3301.sock
port = 3301
pid-file = /usr/local/mysql_3301/data/mysql_3301.pid
datadir = /usr/local/mysql_3301/data/
log = /usr/local/mysql_3301/data/mysql_3301.log
user = mysql

[mysqld2]
socket = /tmp/mysql_3302.sock
port = 3302
pid-file = /usr/local/mysql_3302/data/mysql_3302.pid
datadir = /usr/local/mysql_3302/data/
log = /usr/local/mysql_3302/data/mysql_3302.log
user = mysql

啟動mysqld 的兩個實例

/usr/bin/mysqld_multi –config-file=./my_multi.cnf start 1,2

Starting mysqld daemon with databases from /usr/local/mysql_3301/data/
Starting mysqld daemon with databases from /usr/local/mysql_3302/data/

查看3301,3302端口是否被監聽
# netstat -lt |grep 33
tcp 0 0 *:3301 *:* LISTEN
tcp 0 0 *:3302 *:* LISTEN

測試mysql是否可以連通

#pwd
/usr/local/
通過/tmp/mysql_3301.sock連接3001端口的mysqld
# bin/mysql -u root -S /tmp/mysql_3301.sock -e “SELECT @@VERSION;”
停止3001端口的mysqld
# /usr/bin/mysqld_multi –config-file=./my_multi.cnf stop 1
STOPPING server from pid file /usr/local/mysql_3301/data/mysql_3301.pid
091010 11:56:04 mysqld ended
再次連接,系統會提示錯誤
# bin/mysql -u root -S /tmp/mysql_3301.sock -e “SELECT @@VERSION;”
ERROR 2002 (HY000):
Can’t connect to local MySQL server through socket ‘/tmp/mysql_3301.sock’ (2)
相同的步驟測試3002端口的mysqld，輸出與上面相同。
# /usr/bin/mysql -u root -S /tmp/mysql_3302.sock -e “SELECT @@VERSION;”
# /usr/bin/mysqld_multi –config-file=./my_multi.cnf stop 2
# /usr/bin/mysql -u root -S /tmp/mysql_3302.sock -e “SELECT @@VERSION;”

補充上兩句：
[Nova@imdba.cn mysql]# cp ../mysql-5.0.67/support-files/my-large.cnf /etc/my.cnf
[Nova@imdba.cn mysql]# cp ../mysql-5.0.67/support-files/mysql.server /etc/rc.d/init.d/mysqld
[Nova@imdba.cn mysql]# chkconfig –add mysql
[Nova@imdba.cn mysql]# chkconfig –level mysql 345 on
[Nova@imdba.cn mysql]# chkconfig –list mysql

轉載于:https://www.cnblogs.com/wajika/p/6242087.html

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