sudo apt autoremove --purge mysql-server-*
sudo apt remove mysql-server
sudo apt autoremove mysql-server
sudo apt remove mysql-common

sudo apt-get update #更新包
sudo apt install mysql-server-5.7

#1
VALIDATE PASSWORD PLUGIN can be used to test passwords...
Press y|Y for Yes, any other key for No: N 
 
#2
 Please set the password for root here...
 New password: (输入密码)
Re-enter new password: (重复输入)
 
#3
 By default, a MySQL installation has an anonymous user,
 allowing anyone to log into MySQL without having to have
 a user account created for them...
 Remove anonymous users? (Press y|Y for Yes, any other key for No) : N 
 
#4
 Normally, root should only be allowed to connect from
 'localhost'. This ensures that someone cannot guess at
 the root password from the network...
 Disallow root login remotely? (Press y|Y for Yes, any other key for No) : N 
 
#5
 By default, MySQL comes with a database named 'test' that
 anyone can access...
 Remove test database and access to it? (Press y|Y for Yes, any other key for No) : N 
 
#6
 Reloading the privilege tables will ensure that all changes
 made so far will take effect immediately.
 Reload privilege tables now? (Press y|Y for Yes, any other key for No) : Y

sudo cat /etc/mysql/debian.cnf  # 查看 Password 后面的密码
mysql -u debian-sys-maint -p    #进入 mysql 命令模式
mysql> use mysql;
mysql> select user,host,authentication_string from user;
mysql> update mysql.user set authentication_string=password('密码') where user='root' and Host ='localhost';
mysql> update user set plugin='mysql_native_password'; //注意别更新错了，错了客户端工具就连不上了
mysql> select Host, User, plugin from user;
mysql> flush privileges;
mysql> quit;

sudo vi /etc/mysql/mysql.conf.d/mysqld.cnf
:wq
mysql -uroot -p
mysql> use mysql;
mysql> update user set host='%' where user = 'root';
mysql> flush privileges;

#重启
sudo service mysql restart  
#查看状态
systemctl status mysql.service