系统centos5.5
进入http://dev.mysql.com/downloads/repo/，下载RedHat Enterprise Linux 5 / Oracle Linux 5版。
点击链接No thanks, just start my download.直接下载。
导入系统：sudo yum localinstall mysql-community-release-el5-*.noarch.rpm
您可能遇到这个问题：
warning: rpmts_HdrFromFdno: V3 DSA signature: NOKEY, key ID 443e1821
Public key for krb5-workstation-1.3.4-27.i386.rpm is not installed
解决方法：
/etc/yum.conf Were it sais gpgcheck=1, change this to gpgcheck=0.
groupadd mysql # 创建msyql组
useradd -g mysql mysql
参考资料：https://www.digitalocean.com/community/tutorials/how-to-install-mysql-5-6-from-official-yum-repositories
安装完毕后
service mysqld start报错
/usr/sbin/mysqld: Can't find file: './mysql/plugin.frm' (errno: 13 - Permission denied),提示没有目录权限
更改datadir目录权限：chown -R mysql:mysql /var/lib/mysql
start继续报错
/usr/sbin/mysqld: Table 'mysql.plugin' doesn't exist
去datadir目录，表确实不存在
执行建表：/usr/bin/mysql_install_db --user=mysql
再次启动，成功
