不允许登录，同一时间仅允许一个IP进行一个连接。
Not logged in, only 1 session from same IP allowed at a time.
如果你的公司不允许登录这些网站，或许你就会把精力用在寻找代理网站，以登录到被公司屏蔽掉的网站上。
If your company doesn't allow access to these sites, perhaps your energies are focused on finding proxy sites which allow you to access sites that have been blocked by your company.
最后一行不允许任何人作为根用户登录，这会让黑客攻击更困难。
Finally, the last line doesn't allow anybody to log in as root, making life a bit more difficult for hackers.
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