cat /etc/apt/sources.list的正确输出是什么
我有ubuntu 12.04 lts，我需要正确的输出，因为我编辑它因为它不起作用但它只是让它变得更糟，谢谢你的帮助
以下是Ubuntu 12.04的标准/etc/apt/sources.list文件的简单示例：
deb http://archive.ubuntu.com/ubuntu precise main universe restricted multiverse deb http://archive.ubuntu.com/ubuntu precise-security universe main multiverse restricted deb http://archive.ubuntu.com/ubuntu precise-updates universe main multiverse restricted deb http://archive.ubuntu.com/ubuntu precise-proposed universe main multiverse restricted
编辑sources.list文件的最简单方法是使用以下命令从nano编辑器中的终端：
sudo nano /etc/apt/sources.list
使用nano的说明始终显示在页面底部。 使用键盘组合Ctrl + O ，然后按Enter键将文件保存到其当前位置。 使用键盘组合Ctrl + X退出nano。
Ubuntu 16.04的标准sources.list文件如下所示：
deb http://archive.ubuntu.com/ubuntu/ xenial main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ xenial-updates main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse deb http://security.ubuntu.com/ubuntu xenial-security main restricted universe multiverse deb http://archive.canonical.com/ubuntu xenial partner
Ubuntu 18.04的标准sources.list文件如下所示：
deb http://archive.ubuntu.com/ubuntu/ bionic main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse deb http://security.ubuntu.com/ubuntu bionic-security main restricted universe multiverse deb http://archive.canonical.com/ubuntu bionic partner