申请了两台Redhat虚拟机做cobar的实验，空空如也什么都得装。原来在3个Arch上实现了3个datanode，想在Redhat上每个3个总共配6个Mysql实例。
复制多个实例
在/var/lib目录下找到Mysql目录，将其复制两份，以端口号作后缀以区分：
cp -r /var/lib/mysql /var/lib/mysql3307
cp -r /var/lib/mysql /var/lib/mysql3308
chown -R mysql mysql3307
chown -R mysql mysql3308
配置参数
Mysql的配置文件是/etc/my.cnf,但是默认是没有的，在/usr/share/mysql/目录下有5个.cnf后缀的文件，可以根据自己机器内存大小选择一个文件复制为/etc/my.cnf:
/usr/share/mysql/my-small.cnf 64M内存
/usr/share/mysql/my-medium.cnf 128M内存
/usr/share/mysql/my-large.cnf 512M内存
/usr/share/mysql/my-huge.cnf 1-2G内存
/usr/share/mysql/my-innodb-heavy-4G.cnf 4G内存
我将my-huge.cnf复制为my.cnf。
酌情添加以下配置：
[mysqld_multi]
mysqld = /usr/bin/mysqld_safe
mysqladmin = /usr/bin/mysqladmin
[mysqld1]
port = 3306
socket = /var/lib/mysql/mysql.sock
pid-file = /var/lib/mysql/mysql.pid
datadir = /var/lib/mysql
user = mysql
skip-external-locking
key_buffer_size = 384M
max_allowed_packet = 1M
table_open_cache = 512
sort_buffer_size = 2M
read_buffer_size = 2M
read_rnd_buffer_size = 8M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size = 32M
server-id = 1
[mysqld2]
port = 3307
socket = /var/lib/mysql3307/mysql.sock
pid-file = /var/lib/mysql3307/mysql.pid
datadir = /var/lib/mysql3307
user = mysql
skip-external-locking
key_buffer_size = 384M
max_allowed_packet = 1M
table_open_cache = 512
sort_buffer_size = 2M
read_buffer_size = 2M
read_rnd_buffer_size = 8M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size = 32M
server-id = 1
[mysqld3]
port = 3308
socket = /var/lib/mysql3308/mysql.sock
pid-file = /var/lib/mysql3308/mysql.pid
datadir = /var/lib/mysql3308
user = mysql
skip-external-locking
key_buffer_size = 384M
max_allowed_packet = 1M
table_open_cache = 512
sort_buffer_size = 2M
read_buffer_size = 2M
read_rnd_buffer_size = 8M
myisam_sort_buffer_size = 64M
thread_cache_size = 8
query_cache_size = 32M
server-id = 1
要注意其中的mysqld、mysqladmin后配置的目录参数视具体情况而定。
配置完将3个Mysql都启动：
mysqld_multi start
成功~