[ubuntu] sudo：无法解析主机问题

在/etc/hosts 里追加如下：

127.0.1.1 hostname

为什么要这么设定，参照：

http://www.debian.org/doc/manuals/debian-reference/ch05.en.html#s-net-dns

The IP address

127.0.1.1

in the second line of this example may not be found on some other Unix-like systems. TheDebian Installer
creates this entry for a system without a permanent IP address as a workaround for some software (e.g., GNOME) as documented in thebug #719621.