我使用的版本是 18
sodu gedit /etc/apt/sources.list
#清华大学
# deb cdrom:[Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)]/ xenial main restricted
# deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted
# deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial universe
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates universe
# deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial multiverse
# deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates multiverse
# deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe #multiverse
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security universe
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security multiverse