[root@centos-linux ~]# cat /var/log/mysqld.log | grep 'password'
2016-07-16T03:07:53.587995Z 1 [Note] A temporary password is generated for root@localhost: 2=s6NZk.t:fz

mysql> show databases;
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY '123';
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements

mysql> show variables like 'vali%';
+--------------------------------------+--------+
| Variable_name            | Value |
+--------------------------------------+--------+
| validate_password_dictionary_file  |    | 
| validate_password_length       | 8   | 
| validate_password_mixed_case_count  | 1   |
| validate_password_number_count    | 1   |
| validate_password_policy       | MEDIUM |
| validate_password_special_char_count | 1   |
+--------------------------------------+--------+
6 rows in set (0.01 sec)

validate_password_length
# 密碼的最小長度，默認為8。
validate_password_mixed_case_count
# 至少要包含小寫或大寫字母的個數，默認為1。
validate_password_number_count
# 至少要包含的數字的個數，默認為1。
validate_password_policy 
# 強度等級，可設置為0、1、2。
  【0/LOW】：只檢查長度。
  【1/MEDIUM】：在0等級的基礎上多檢查數字、大小寫、特殊字符。
  【2/STRONG】：在1等級的基礎上多檢查特殊字符字典文件，此處為1。
validate_password_special_char_count
# 至少要包含的特殊字符的個數，默認為1。