ubuntu18首次安装mysql没有设置密码

mahao@ubuntu:~$ sudo cat /etc/mysql/debian.cnf
# Automatically generated for Debian scripts. DO NOT TOUCH!
[client]
host     = localhost
user     = debian-sys-maint
password = TCUpCFTUFypDLka4
socket   = /var/run/mysqld/mysqld.sock
[mysql_upgrade]
host     = localhost
user     = debian-sys-maint
password = TCUpCFTUFypDLka4  //注意此条信息
socket   = /var/run/mysqld/mysqld.sock
mahao@ubuntu:~$ mysql -u debian-sys-maint -pTCUpCFTUFypDLka4 //这条指令的密码输入是password = TCUpCFTUFypDLka4
mysql> use mysql;
mysql> update mysql.user set authentication_string=password('123456') where user='root' and Host ='localhost';
mysql> update user set plugin="mysql_native_password"; 
mysql> flush privileges;
mysql> quit;

mahao@ubuntu:~$ sudo service mysqld restart //重启服务