Ubuntu20 安装 MySQL8.0 版本，使用 sudo mysql 无密码登录。

sudo mysql -uroot -p
# 无需输入密码，直接 Enter 即可进入
mysql> 

输入密码

mysql> use mysql;
mysql> select user,host from user;
+------------------+-----------+
| user             | host      |
+------------------+-----------+
| root             | %         |
| admin            | localhost |
| mysql.infoschema | localhost |
| mysql.session    | localhost |
| mysql.sys        | localhost |
| zhangj           | localhost |
+------------------+-----------+

mysql> ALTER USER 'root'@'%' IDENTIFIED WITH mysql_native_password BY '123456';

重新打开终端，输入用户名密码登录。

mysql -uroot -p
Enter password ******
mysql>