[Ubuntu -- MySQL] Can I log on to MySQL without verification?

Configure MySQL password in Ubuntu

System Environment:
Linux Ubuntu 3.5.0-27-generic # 46-ubuntu SMP mon Mar 25 20:00:05 UTC 2013 i686 i686 i686 GNU/Linux
MySQL ver 14.14 distrib 5.5.29, for Debian-Linux-GNU (i686) using Readline 6.2

After MySQL is installed, you are not allowed to connect to a password...
Is there a default password or what is going on?
Try it now
Lzz @ Ubuntu:/var/lib/dpkg/INFO $ sudo mysql-u root-P
Enter password:
Welcome to the MySQL monitor. commands end with; or \ G.
Your MySQL connection ID is 45
Server version: 5.5.29-0ubuntu0. 12.10.1 (UBUNTU)

Come in. (In fact, the password has been set this time... I still don't know what's going on. I won't be able to get in the next time I enter without a password)

Lzz @ Ubuntu:/var/lib/dpkg/INFO $ mysql
Welcome to the MySQL monitor. commands end with; or \ G.
Your MySQL connection ID is 46
Server version: 5.5.29-0ubuntu0. 12.10.1 (UBUNTU)

Also come in. What is the difference between passwords? Check the information to see what is going on.

It turns out that there is a default user and password.
Lzz @ Ubuntu:/etc/MySQL $ sudo cat Debian. CNF
# Automatically generated for Debian scripts. Do not touch!
[Client]
Host = localhost
User = Debian-sys-Maint
Password = iyeuej0gy5ml42l5
Socket =/var/run/mysqld. Sock
[Mysql_upgrade]
Host = localhost
User = Debian-sys-Maint
Password = iyeuej0gy5ml42l5
Socket =/var/run/mysqld. Sock
Basedir =/usr

Find this post:
Installation Security:
The default is terrible.
Hack MYSQL:

MySQL is installed by default, and super users can log on without a password
Anonymous Access
Provide superuser and password in the configuration file
Shell with password login, history file
Unauthorized users can access the MySQL permission table: the entire MySQL database
Can start and stop the mysqld process, and can reset the password: -- skip-grant-tables
Brute force check
The application uses a plaintext password, and the user may have certain privileges.
Damage MYSQL:
CPU stealing cycle: Select MD5 (A. C), MD5 (B. C) from a, B order by rand ();
Forced disk I/O: Set session tmp_table_size = 1024*4;

Anonymous Access

Minimum: $ mysql_secure_installation
Remove anonymous users
Remove test database
Remove non-localhost Root User
Set Root Password

For MySQL, a simple operation such as adding, deleting, and so on will be performed at the beginning, and Oracle will be involved. user permission management is a big problem and should be standardized. check whether there are related installation and configuration specifications later.