一 使用ubuntu维护版本安装：
http://manpages.ubuntu.com/manpages/xenial/man8/sudo_root.8.html
ENEFITS OF USING SUDO
The benefits of leaving root disabled by default include the following:
* Users do not have to remember an extra password,which they are
likely to forget.
* The installer is able to ask fewer questions.
* It avoids the "I can do anything" interactive login by default - you
will be prompted for a password before major changes can happen,which should make you think about the consequences of what you are
doing.
* Sudo adds a log entry of the command(s) run (in /var/log/auth.log).
* Every attacker trying to brute-force their way into your Box will
know it has an account named root and will try that first. What they
do not know is what the usernames of your other users are.
* Allows easy transfer for admin rights,in a short term or long term
period,by adding and removing users from the sudo group,while not
compromising the root account.
* sudo can be set up with a much more fine-grained security policy.
* On systems with more than one administrator using sudo avoids sharing
a password amongst them.
