修改密码
1.查看初始密码
grep 'temporary password' /var/log/mysqld.log
2.连接 MySQL， 输入下面代码， 回车后输入上面密码
mysql -uroot -p
3.选数据库
use mysql;
4.将authentication_string置空
update user set authentication_string='' where user='root';
注：在mysql8.0以上版本，
update mysql.user set password='newpassword' where user='root';
update mysql.user set password=PASSWORD('newpassword') where User='root';
这两条命令已经不起作用了
5.修改密码
ALTER USER 'root'@'localhost' IDENTIFIED BY '新密码';
会出现报错如下：
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
这个其实与validate_password_policy的值有关
有以下取值：
| Policy | Tests Performe（要求) |
|---|---|
| 0 or LOW | Length |
| 1 or MEDIUM | numeric, lowercase/uppercase, and special characters |
| 2 or STRONG | Length; numeric, lowercase/uppercase, and special characters |
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。
有时候，只是为了自己测试，不想密码设置得那么复杂，譬如说，我只想设置root的密码为123123.
这是时候，Wimbledon可以在第一次使用进入数据库的时候修改几个全局变量就行，或者再次跳过权限表进入到数据库！
mysql> show variables like "%validate%";
+--------------------------------------+--------+
| Variable_name | Value |
+--------------------------------------+--------+
| query_cache_wlock_invalidate | OFF |
| validate_password_check_user_name | OFF |
| validate_password_dictionary_file | |
| validate_password_length | 8 | ##密码的最小长度，改成6
| validate_password_mixed_case_count | 1 |
| validate_password_number_count | 1 |
| validate_password_policy | MEDIUM | #这个改成0，就可以接受简单的密码
| validate_password_special_char_count | 1 |
+--------------------------------------+--------+
#修改全局变量
mysql> set global validate_password_length=6;
Query OK, 0 rows affected (0.00 sec)
mysql> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)
mysql> show variables like "%validate%";
+--------------------------------------+-------+
| Variable_name | Value |
+--------------------------------------+-------+
| query_cache_wlock_invalidate | OFF |
| validate_password_check_user_name | OFF |
| validate_password_dictionary_file | |
| validate_password_length | 6 |
| validate_password_mixed_case_count | 1 |
| validate_password_number_count | 1 |
| validate_password_policy | LOW |
| validate_password_special_char_count | 1 |
+--------------------------------------+-------+
8 rows in set (0.00 sec)
mysql> alter user 'root'@'localhost' identified by '123123'; #重新修改密码，不会再有错误！
Query OK, 0 rows affected (0.01 sec)
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