[root@uat01 ~]# cat InstallMysql01.sh 
#!/bin/bash
#2018-10-13
#旅行者-Travel
#1.安装wget
yum -y install wget
#2、下载mysql的yum源
URL="https://repo.mysql.com//mysql80-community-release-el7-1.noarch.rpm"
wget $URL -P /etc/yum.repos.d/
yum -y install yum-utils #如果没有该包，下边执行yum-config-manager不生效
yum -y install /etc/yum.repos.d/mysql80-community-release-el7-1.noarch.rpm
 if [ $? -eq 0 ];then
  rm -rf /etc/yum.repos.d/mysql80-community-release-el7-1.noarch*
 fi
yum-config-manager --disable mysql80-community
yum-config-manager --enable mysql57-community
yum -y install mysql-community-server
 sleep 5
 systemctl start mysqld 
 systemctl enable mysqld
 systemctl status mysqld
 if [ $? -eq 0 ];then
  echo -e "install succefull"
  result="`grep 'temporary password' /var/log/mysqld.log`"
  p1="`echo $result |awk '{print $NF}'`"
  echo "数据库密码为:$p1"
 
 fi
[root@uat01 ~]# 

install succefull
数据库密码为:9aTR&ok>f;1K
[root@uat01 ~]# mysql -uroot -p
Enter password: 
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.23

Copyright (c) 2000, 2018, 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> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_length=4;
Query OK, 0 rows affected (0.00 sec)

mysql> alter user 'root'@'localhost' identified by 'Yanglt123.';
Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> quit

[root@uat01 ~]# mysql -uroot -p
.....
Server version: 5.7.23 MySQL Community 
......
mysql> show variables like 'validate_password%';
+--------------------------------------+-------+
| Variable_name      | Value |
+--------------------------------------+-------+
| validate_password_check_user_name | OFF |
| validate_password_dictionary_file |  |
| validate_password_length    | 4  |
| validate_password_mixed_case_count | 1  |
| validate_password_number_count  | 1  |
| validate_password_policy    | LOW |
| validate_password_special_char_count | 1  |
+--------------------------------------+-------+
7 rows in set (0.00 sec)

mysql> 

mysql> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)
mysql> set global validate_password_length=4;
Query OK, 0 rows affected (0.00 sec),
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql> alter user 'root'@'localhost' identified by '1234'; #测试发现密码长度最少为4位
Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

mysql> quit
Bye
[root@uat01 ~]# mysql -p
Enter password: 
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.23 MySQL Community Server (GPL)

Copyright (c) 2000, 2018, 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>