1.删除原有的mariadb，不然mysql装不进去

mariadb-libs-5.5.52-1.el7.x86_64

rpm -qa|grep mariadb

rpm -e –nodeps mariadb-libs

1.在https://dev.mysql.com/downloads/mysql/选择为Red Hat Enterprise Linux 7 / Oracle Linux 7 ，把os的版本选择为all。 

直接下载mysql-5.7.21-1.el7.x86_64.rpm-bundle.tar，所有的rpm包都在里面

rpm -ivh mysql-community-common–5.7.21–1.el7.x86_64.rpm

rpm -ivh mysql-community-libs–5.7.21–1.el7.x86_64.rpm

rpm -ivh mysql-community-devel–5.7.21–1.el7.x86_64.rpm

rpm -ivh mysql-community-libs-compat–5.7.21–1.el7.x86_64.rpm

rpm -ivh mysql-community-client–5.7.21–1.el7.x86_64.rpm

rpm -ivh mysql-community-server–5.7.21–1.el7.x86_64.rpm

至此，mysql5.7所有文件安装完毕，接下来就是开启服务测试了。 
1.首先关闭mysql服务：

service mysqld stop

2.然后修改配置文件：

vim /etc/my.cnf

3.接下来加入一句代码即可空密码登录mysql：

# Disabling symbolic-links is recommended to prevent assorted security risks skip-grant-tables #添加这句话，这时候登入mysql就不需要密码 symbolic-links=0

4.开启mysql服务：

service mysqld start

5.空密码登录mysql：

mysql -u root -p    #输入命令回车进入，出现输入密码提示直接回车

6.设置mysql密码：

mysql> set password for root@localhost = password('123456'); ERROR 1290 (HY000): The MySQL server is running with the --skip-grant-tables option so it cannot execute this statement mysql> flush privileges; #更新权限 Query OK, 0 rows affected (0.00 sec) mysql> set password for root@localhost = password('123456');  Query OK, 0 rows affected, 1 warning (0.00 sec) mysql>flush privileges; #更新权限 mysql>quit; #退出 service mysqld stop # 停止mysql服务, 恢复mysql配置 vim /etc/my.cnf #修改配置文件 # Disabling symbolic-links is recommended to prevent assorted security risks # skip-grant-tables # 注释掉这句话 symbolic-links=0 service mysqld start # 启动mysql服务 mysql -uroot -p # 输入新密码登录

7.设置mysql开机自启：

systemctl enable mysqld