终端输入 gksudo gedit /etc/apt/sources.list
输入密码
把内容全删,换成
deb
http://free.nchc.org.tw/ubuntu trusty main restricted universe multiverse
deb
http://free.nchc.org.tw/ubuntu trusty-updates main restricted universe multiverse
deb
http://free.nchc.org.tw/ubuntu trusty-backports main restricted universe multiverse
deb
http://free.nchc.org.tw/ubuntu trusty-security main restricted universe multiverse
就这四行。存档关闭,然后sudo apt-get update