文件/etc/apt/source.list内容

#/etc/apt
# deb cdrom:[Ubuntu 14.04.4 LTS _Trusty Tahr_ - Release i386 (20160217.1)]/ xenial main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb https://mirrors.aliyun.com/ubuntu/ xenial main restricted
deb-src https://mirrors.aliyun.com/ubuntu/ xenial main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb https://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted
deb-src https://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb https://mirrors.aliyun.com/ubuntu/ xenial universe
deb-src https://mirrors.aliyun.com/ubuntu/ xenial universe
deb https://mirrors.aliyun.com/ubuntu/ xenial-updates universe
deb-src https://mirrors.aliyun.com/ubuntu/ xenial-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb https://mirrors.aliyun.com/ubuntu/ xenial multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ xenial multiverse
deb https://mirrors.aliyun.com/ubuntu/ xenial-updates multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ xenial-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb https://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse

deb https://mirrors.aliyun.com/ubuntu/ xenial-security main restricted
deb-src https://mirrors.aliyun.com/ubuntu/ xenial-security main restricted
deb https://mirrors.aliyun.com/ubuntu/ xenial-security universe
deb-src https://mirrors.aliyun.com/ubuntu/ xenial-security universe
deb https://mirrors.aliyun.com/ubuntu/ xenial-security multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ xenial-security multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb https://archive.canonical.com/ubuntu xenial partner
# deb-src https://archive.canonical.com/ubuntu xenial partner

## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
#deb https://mirrors.aliyun.com/ubuntu xenial main
#deb-src https://mirrors.aliyun.com/ubuntu xenial main

是由trusty改为xenial

/etc/NetworkManager/NetworkManager.conf       false改为true

/etc/resolv.conf     添加116.116.116.116

后apt-get update 成功！