ubunto自己不须要用root帐户和ubunto root默认密码

By default Ubuntu does not set up a root password and therefore you don't get the ability to log in as root. Instead you are given the ability to perform tasks with superuser privileges using sudo.

Ubunto自己没有设置root 帐户的密码，因此你也没法以root身份登陆进去。

I've answered a similar question before.

While you can create a password for the root account allowing you to log in as root with su, this isn't the typical "Ubuntu" way of doing things. Instead Ubuntu expects that you will be using sudo.

Ubunto但愿你是一sudo 方式来增长特殊权限去执行一些命令。

Sudo is an alternative to giving people a root password in order to perform superuser duties. In a default Ubuntu install the person who installed the OS is given "sudo" permission by default.

默认状况下安装Ubuntu的帐户是有sudo权限的

Anybody with "sudo" permission may perform something "as a superuser" by pre-pending sudo to their command. For instance, to run apt-get dist-upgrade as a superuser, you could use:

sudo apt-get dist-upgrade

You will see this usage of sudo pretty much anywhere you read a tutorial about Ubuntu on the web. It's an alternative to doing this.

su
apt-get dist-upgrade
exit

With sudo, you choose in advance which users have sudo access. There is no need for them to remember a root password, as they use their own password. If you have multiple users, you can revoke one's superuser access just by removing their sudo permission, without needing to change the root password and notify everyone of a new password. You can even choose which commands a user is allowed to perform using sudo and which commands are forbidden for that user. And lastly, if there is a security breach it can in some cases leave a better audit trail showing which user account was compromised.

Sudo makes it easier to perform a single command with superuser privileges. With su, you permanently drop to a superuser shell which must be exited using exit or logout. This can lead to people staying in the superuser shell for longer than necessary just because it's more convenient than logging out and in again later.

With sudo, you still have the option of opening a permanent (interactive) superuser shell with the command:

sudo su

... and this can still be done without any root password, because sudo gives superuser privileges to the su command.

And similarly, instead of su - for a login shell you can use sudo su - or even sudo -i.

However when doing so you just need to be aware that you are acting as a superuser for every command. It's a good security principle not to stay as a superuser for longer than necessary, just to lessen the possibility of accidentally causing some damage to the system (without it, you can only damage files your user owns).

Just to clarify, you can, if you choose, give the root user a password allowing logins as root, if you specifically want to do things this way instead. I just wanted to let you know about the Ubuntu convention of preferring sudo instead and let you know that there is an alternative.