准备安装包

mysql-community-client-5.7.28-1.el7.x86_64.rpm
mysql-community-common-5.7.28-1.el7.x86_64.rpm
mysql-community-libs-5.7.28-1.el7.x86_64.rpm
mysql-community-server-5.7.28-1.el7.x86_64.rpm

依次安装

yum remove mariadb
yum install net-tools
rpm -ivh mysql-community-common-5.7.28-1.el7.x86_64.rpm
rpm -ivh mysql-community-libs-5.7.28-1.el7.x86_64.rpm
rpm -ivh mysql-community-client-5.7.28-1.el7.x86_64.rpm
rpm -ivh mysql-community-server-5.7.28-1.el7.x86_64.rpm
rpm -ivh mysql-community-devel-5.7.28-1.el7.x86_64.rpm
rpm -ivh mysql-community-libs-compat-5.7.28-1.el7.x86_64.rpm
# 其他依赖缺啥yum install啥

启动&开机自启

systemctl enable mysqld
systemctl start mysqld

获取随机root密码

grep password /var/log/mysqld.log
2020-02-27T04:00:21.085146Z 1 [Note] A temporary password is generated for root@localhost: 1Hm%fferpq_:
mysql -u root -p
Enter password: 1Hm%fferpq_:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.28

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show database;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'database' at line 1
# 还无法操作

初始化

• 1. 使用alter修改

mysql> ALTER USER USER() IDENTIFIED BY '1Hm%fferpq_:';
Query OK, 0 rows affected (0.00 sec)
 
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY '112233@AbC';
Query OK, 0 rows affected (0.00 sec)

# 或者先关闭其密码策略修改
mysql> select @@validate_password_length;
+----------------------------+
| @@validate_password_length |
+----------------------------+
|                          8 |
+----------------------------+
1 row in set (0.01 sec)

mysql> select @@validate_password_policy;
+----------------------------+
| @@validate_password_policy |
+----------------------------+
| MEDIUM                     |
+----------------------------+
1 row in set (0.00 sec)
mysql> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)
mysql>  ALTER USER USER() IDENTIFIED BY '12345678';
Query OK, 0 rows affected (0.00 sec)

validate_password_policy有以下取值：
Policy  Tests Performed
0 or LOW    Length
1 or MEDIUM Length; numeric, lowercase/uppercase, and special characters
2 or STRONG Length; numeric, lowercase/uppercase, and special characters; dictionary file
默认是1，即MEDIUM，所以刚开始设置的密码必须符合长度，且必须含有数字，小写或大写字母，特殊字符。

• 2. 使用mysql_secure_installation

mysql_secure_installation
 
Securing the MySQL server deployment.
 
Enter password for user root: 1Hm%fferpq_:
# 下略

创建用户

mysql> use mysql;
mysql> create user 'admin'@'%' identified by '12345678';
Query OK, 0 rows affected (0.00 sec)

授权

grant select ,insert,update on db1.t1 to "admin"@'%';
grant all privileges  on db1.* to "admin"@'%';
grant all privileges  on *.*  to "admin"@'%';

取消授权

revoke all on db1.t1 from 'admin'@"%";  
revoke all on db1.* from 'admin'@"%";  
revoke all privileges on *.* from 'admin'@'%';