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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