之前使用的是 阿里的镜像源
deb http://mirrors.aliyun.com/ubuntu trusty main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu trusty-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu trusty-backports main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu trusty-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu trusty-proposed main restricted universe multiverse
换成 中国科学技术大学源一切正常。
deb http://mirrors.ustc.edu.cn/ubuntu trusty main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu trusty-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu trusty-backports main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu trusty-security main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu trusty-proposed main restricted universe multiverse