内容源自：CentOS7安装mysql
在CentOS中默认安装有MariaDB，这个是MySQL的分支，但为了需要，还是要在系统中安装MySQL，而且安装完成之后可以直接覆盖掉MariaDB。
1.安装
wget -i -c http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm //下载了安装用的Yum Repository yum -y install mysql57-community-release-el7-10.noarch.rpm yum -y install mysql-community-server
可以看到：安装完毕
Running transaction 正在安装 : mysql-community-common-5.7.22-1.el7.x86_64 1/6 正在安装 : mysql-community-libs-5.7.22-1.el7.x86_64 2/6 正在安装 : mysql-community-client-5.7.22-1.el7.x86_64 3/6 正在安装 : mysql-community-server-5.7.22-1.el7.x86_64 4/6 正在安装 : mysql-community-libs-compat-5.7.22-1.el7.x86_64 5/6 正在删除 : 1:mariadb-libs-5.5.56-2.el7.x86_64 6/6 验证中 : mysql-community-libs-compat-5.7.22-1.el7.x86_64 1/6 验证中 : mysql-community-common-5.7.22-1.el7.x86_64 2/6 验证中 : mysql-community-server-5.7.22-1.el7.x86_64 3/6 验证中 : mysql-community-client-5.7.22-1.el7.x86_64 4/6 验证中 : mysql-community-libs-5.7.22-1.el7.x86_64 5/6 验证中 : 1:mariadb-libs-5.5.56-2.el7.x86_64 6/6 已安装: mysql-community-libs.x86_64 0:5.7.22-1.el7 mysql-community-libs-compat.x86_64 0:5.7.22-1.el7 mysql-community-server.x86_64 0:5.7.22-1.el7 作为依赖被安装: mysql-community-client.x86_64 0:5.7.22-1.el7 mysql-community-common.x86_64 0:5.7.22-1.el7 替代: mariadb-libs.x86_64 1:5.5.56-2.el7 完毕！
记得卸载Yum Repository：
yum -y remove mysql57-community-release-el7-10.noarch
2.MySQL配置
启动：
systemctl start mysqld.service
查看运行状态：
systemctl status mysqld.service
显示为active，即为运行状态：
● mysqld.service - MySQL Server Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled) Active: active (running) since 二 2018-05-29 09:56:21 CST; 15s ago Docs: man:mysqld(8) http://dev.mysql.com/doc/refman/en/using-systemd.html Process: 3886 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS) Process: 3808 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS) Main PID: 3889 (mysqld) Tasks: 27 CGroup: /system.slice/mysqld.service └─3889 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
查看运行初始密码：
grep "password" /var/log/mysqld.log
进入数据库：
mysql -uroot -p
修改初始密码：
mysql> set global validate_password_policy=0; mysql> set global validate_password_length=1; //因为MySQL有密码设置的规范，具体是与validate_password_policy的值有关，上面是为了修改密码规范，使密码设置可以设置很简单 //修改密码：
mysql>SET PASSWORD = PASSWORD('mysql');
mysql>flush privileges;