修改sources.list
用编辑器打开 /etc/apt/sources.list，在末尾添加源地址，如以下内容
北邮镜像地址
deb ftp://openware.byr.edu.cn/pub/mirror/ubuntu/ precise main multiverse restricted universe
deb ftp://openware.byr.edu.cn/pub/mirror/ubuntu/ precise-backports main multiverse restricted universe
deb ftp://openware.byr.edu.cn/pub/mirror/ubuntu/ precise-proposed main multiverse restricted universe
deb ftp://openware.byr.edu.cn/pub/mirror/ubuntu/ precise-security main multiverse restricted universe
deb ftp://openware.byr.edu.cn/pub/mirror/ubuntu/ precise-updates main multiverse restricted universe
virtualbox源
添加网站：https://www.virtualbox.org/wiki/Linux_Downloads
deb http://download.virtualbox.org/virtualbox/debian trusty contrib
deb http://download.virtualbox.org/virtualbox/debian saucy contrib
deb http://download.virtualbox.org/virtualbox/debian raring contrib
deb http://download.virtualbox.org/virtualbox/debian quantal contrib
deb http://download.virtualbox.org/virtualbox/debian precise contrib
deb http://download.virtualbox.org/virtualbox/debian lucid contrib non-free
deb http://download.virtualbox.org/virtualbox/debian wheezy contrib
deb http://download.virtualbox.org/virtualbox/debian squeeze contrib non-free
#添加key
wget -q https://www.virtualbox.org/download/oracle_vbox.asc -O- | sudo apt-key add -
add-apt-repository
该命令脚本添加ppa到当前的库中并自动导入公钥
gcc/g++ 最新版仓库：
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
当从源获取数据错误时
如遇到： The following signatures were invalid: BADSIG ... 等时执行以下命令：
sudo -s -H
apt-get clean
rm /var/lib/apt/lists/*
rm /var/lib/apt/lists/partial/*
apt-get clean
apt-get update
如遇到： W:GPG错误：http://debian.ustc.edu.cn lucid Release: 运行 gpgv 时发生未知错误 时解决方法：
mkdir temp
sudo mv /usr/local/lib/libreadline* temp
sudo ldconfig
sudo apt-get update