1、备份源
# sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak

2、编辑源文件/etc/apt/sources.list，并添加以下地址
# sudo gedit /etc/apt/sources.list

网易163源：
deb http://mirrors.163.com/ubuntu/ trusty main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-backports main restricted universe multiverse

搜狐源：
deb http://mirrors.sohu.com/ubuntu/ trusty main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-security main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-backports main restricted universe multiverse

oschina源：
deb http://mirrors.oschina.net/ubuntu/ trusty main restricted universe multiverse
deb http://mirrors.oschina.net/ubuntu/ trusty-backports main restricted universe multiverse
deb http://mirrors.oschina.net/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://mirrors.oschina.net/ubuntu/ trusty-security main restricted universe multiverse
deb http://mirrors.oschina.net/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://mirrors.oschina.net/ubuntu/ trusty main restricted universe multiverse
deb-src http://mirrors.oschina.net/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.oschina.net/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://mirrors.oschina.net/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://mirrors.oschina.net/ubuntu/ trusty-updates main restricted universe multiverse

3、 更新源索引，使新源生效
# sudo apt-get update