直接编辑：sudo /etc/apt/sources.list文件
deb http://源地址/ubuntu/ xenial main universe restricted multiverse
deb http://源地址/ubuntu/ xenial-updates main universe restricted multiverse
deb http://源地址/ubuntu/ xenial-backports main restricted universe multiverse
deb http://源地址/ubuntu/ xenial-security main universe restricted multiverse
deb http://源地址/ubuntu/ xenial-proposed main universe restricted multiverse
改完后运行：sudo apt-get update更新索引
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