MySQL 5.7不再弹出root密码设置
sudo vi /etc/mysql/debian.cnf

显示：

Automatically generated for Debian scripts. DO NOT TOUCH!

[client]
host = localhost
user = debian-sys-maint
password = fPw**********22
socket = /var/run/mysqld/mysqld.sock
[mysql_upgrade]
host = localhost
user = debian-sys-maint
password =fPw**********22
socket = /var/run/mysqld/mysqld.sock

找到了，用户名：debian-sys-maint，密码：fPw**********22（这是随机生成的）
退出来，Esc键，输入“：q!”
mysql -u debian-sys-maint -p
Enter password:输入刚才找到的密码

接下来，设置root用户密码（假设为123456）

mysql> update mysql.user set authentication_string=PASSWORD(“123456″) where User=’root’;
更改root密码，然后出现
Query OK, 1 row affected, 1 warning (0.12 sec)
Rows matched: 1 Changed: 1 Warnings: 1

mysql> update mysql.user set plugin=”mysql_native_password”;
解决出现警告的问题，然后出现
Query OK, 1 row affected (0.02 sec)
Rows matched: 4 Changed: 1 Warnings: 0

mysql> flush privileges;
更新所有权限，然后出现
Query OK, 0 rows affected (0.33 sec)

mysql> quit;

退出来，先关闭再启动MySQL
sudo /etc/init.d/mysql stop
sudo /etc/init.d/mysql start

用root用户和密码进去看看
mysql -u root -p

Reference:http://tieba.baidu.com/p/5679939196