有时候我们需要在一个服务器上安装两个mysql，一个应对GBK编码数据，一个应对UTF-8编码数据。此文内容就是应对这种情况。(采用此命令带参数来创建数据库实例，可以减少一些不必要的过程。网络上的一些文章都用默认配置创建数据库实例，以致需要多次重启数据库。)

　　首先我们来学习一下mysql_install_db的帮助信息

通过命令$>mysql_install_db --help 打印如下信息

Usage: /usr/local/mysql/bin/mysql_install_db [OPTIONS] --basedir=path The path to the MySQL installation directory. --cross-bootstrap For internal use. Used when building the MySQL system tables on a different host than the target. --datadir=path The path to the MySQL data directory. --force Causes mysql_install_db to run even if DNS does not work. In that case, grant table entries that normally use hostnames will use IP addresses. --ldata=path The path to the MySQL data directory. --rpm For internal use. This option is used by RPM files during the MySQL installation process. --skip-name-resolve Use IP addresses rather than hostnames when creating grant table entries. This option can be useful if your DNS does not work. --srcdir=path For internal use. The directory under which mysql_install_db looks for support files such as the error message file and the file for popoulating the help tables. --user=user_name The login username to use for running mysqld. Files and directories created by mysqld will be owned by this user. You must be root to use this option. By default mysqld runs using your current login name and files and directories that it creates will be owned by you. All other options are passed to the mysqld program

下面以创建一个UTF-8编码的mysql数据库为例子来说名这个命令的一些使用：

　　首先我们可以通过执行“ cp /etc/my.conf  /etc/my_utf8.conf ”复制一份配置，然后修改配置，确保端口(port),数据路径(datadir),套接字(socket),错误日志路径(log-error),pid-file原来的配置不冲突。下面的是此次修改后配置文件，并增加了一些定制配置以适应应用要求。

[mysqld] datadir=/var/lib/mysql_utf8 socket=/var/lib/mysql/mysql_utf8.sock user=mysql # Default to using old password format for compatibility with mysql 3.x # clients (those using the mysqlclient10 compatibility package). old_passwords=1 skip-locking max_allowed_packet = 5M net_buffer_length = 8K port=3307 default-character-set=utf8 lower_case_table_names=1 max_connections=1000 query_cache_size=100M table_cache=256 tmp_table_size=50M thread_cache_size=8 myisam_max_sort_file_size=100G myisam_max_extra_sort_file_size=100G myisam_sort_buffer_size=50M key_buffer_size=50M read_buffer_size=1024K read_rnd_buffer_size=4096K sort_buffer_size=4096K innodb_additional_mem_pool_size=10M innodb_flush_log_at_trx_commit=1 innodb_log_buffer_size=5M innodb_buffer_pool_size=100M innodb_log_file_size=10M innodb_thread_concurrency=8 [mysqld_safe] log-error=/var/log/mysql_utf8.log pid-file=/var/run/mysqld/mysql_utf8.pid

　　然后执行"#>mysql_install_db --defaults-file=/etc/my_utf8.cnf --datadir=/var/lib/mysql_utf8" 命令来创建数据库。

#>mysql_install_db --defaults-file=/etc/my_utf8.cnf --datadir=/var/lib/mysql_utf8

其中我们用“--defaults-file”指定了创建数据库用到的配置文件；“--datadir”指定创建数据的路径，这里的路径保持与配置文件中的datadir保持一致。

　　观察输出的内容，看看是否有错误信息，如果有的话，观察日志调整配置解决,一般情况都是my_utf8.conf文件的问题。

　　然后执行一下命令来启动数据库：

#>mysqld_safe --defaults-file=/etc/my_utf8.cnf &

　　通过执行下面命令来查询数据是否启动,如果显示有“mysql_utf8”字样的内容就说明数据库启动成功了。

#>ps aux | grep mysql

　　如果需要数据库随服务启动而启动，将前面说的的启动命令加入“/etc/rc.local”就可以了。

　　执行下面命令修改数据库root密码：

#>mysqladmin -uroot password 'newpwd' --socket=/var/lib/mysql/mysql_utf8.sock

　　执行下面命令连接数据库：

#>mysql -uroot -p --socket=/var/lib/mysql/mysql_utf8.sock