为了加强安全性，MySQL5.7为root用户随机生成了一个密码
可通过# grep "password" /var/log/mysqld.log 命令获取MySQL的临时密码用该密码登录到服务端后，必须马上修改密码，不然会报错如果只是修改为一个简单的密码，会报以下错误：
mysql> ALTER USER USER() IDENTIFIED BY '12345678';ERROR 1819 (HY000): Your password does not satisfy the current policy requirements这个其实与validate_password_policy的值有关。validate_password_policy有以下取值：
Policy Tests Performed0 or LOW Length1 or MEDIUM Length; numeric, lowercase/uppercase, and special characters2 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。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123456。
必须修改两个全局参数：首先，修改validate_password_policy参数的值
mysql> set global validate_password_policy=0;Query OK, 0 rows affected (0.00 sec)这样，判断密码的标准就基于密码的长度了。这个由validate_password_length参数来决定。mysql> select @@validate_password_length;
+----------------------------+| @@validate_password_length |+----------------------------+| 8 |+----------------------------+1 row in set (0.00 sec)validate_password_length参数默认为8，它有最小值的限制，最小值为：
validate_password_number_count+ validate_password_special_char_count+ (2 * validate_password_mixed_case_count)其中，validate_password_number_count指定了密码中数据的长度，validate_password_special_char_count指定了密码中特殊字符的长度，validate_password_mixed_case_count指定了密码中大小字母的长度。这些参数，默认值均为1，所以validate_password_length最小值为4，如果你显性指定validate_password_length的值小于4，尽管不会报错，但validate_password_length的值将设为4。如下所示：
mysql> select @@validate_password_length;+----------------------------+| @@validate_password_length |+----------------------------+| 8 |+----------------------------+1 row in set (0.00 sec)mysql> set global validate_password_length=1;
Query OK, 0 rows affected (0.00 sec)mysql> select @@validate_password_length;
+----------------------------+| @@validate_password_length |+----------------------------+| 4 |+----------------------------+1 row in set (0.00 sec)如果修改了validate_password_number_count，validate_password_special_char_count，validate_password_mixed_case_count中任何一个值，则validate_password_length将进行动态修改。
mysql> select @@validate_password_length;
+----------------------------+| @@validate_password_length |+----------------------------+| 4 |+----------------------------+1 row in set (0.00 sec)mysql> select @@validate_password_mixed_case_count;
+--------------------------------------+| @@validate_password_mixed_case_count |+--------------------------------------+| 1 |+--------------------------------------+1 row in set (0.00 sec)mysql> set global validate_password_mixed_case_count=2;
Query OK, 0 rows affected (0.00 sec)mysql> select @@validate_password_mixed_case_count;
+--------------------------------------+| @@validate_password_mixed_case_count |+--------------------------------------+| 2 |+--------------------------------------+1 row in set (0.00 sec)mysql> select @@validate_password_length;
+----------------------------+| @@validate_password_length |+----------------------------+| 6 |+----------------------------+1 row in set (0.00 sec)当然，前提是validate_password插件必须已经安装，MySQL5.7是默认安装的。
那么如何验证validate_password插件是否安装呢？可通过查看以下参数，如果没有安装，则输出将为空。
mysql> SHOW VARIABLES LIKE 'validate_password%';
+--------------------------------------+-------+| Variable_name | Value |+--------------------------------------+-------+| validate_password_dictionary_file | || validate_password_length | 6 || validate_password_mixed_case_count | 2 || validate_password_number_count | 1 || validate_password_policy | LOW || validate_password_special_char_count | 1 |+--------------------------------------+-------+6 rows in set (0.00 sec)MySQL用户管理
MySQL 5.7用户管理
1.为用户授权
登录MYSQL（有ROOT权限）授权phplamp用户拥有phplamp数据库的所有权限。>grant all privileges on phplampDB.* to phplamp@localhost identified by '1234';刷新系统权限表mysql>flush privileges;2. 如果想指定部分权限给一用户
mysql>grant select,update on phplampDB.* to phplamp@localhost identified by '1234';mysql>flush privileges;3. 删除用户
@>mysql -u root -p@>密码mysql>DELETE FROM user WHERE User="phplamp" and Host="localhost";mysql>flush privileges;4. 修改指定用户密码
@>mysql -u root -p@>密码mysql>update mysql.user set password=password('新密码') where User="phplamp" and Host="localhost";mysql>flush privileges;