ubuntu16.04.2默认软件源

进入/etc/apt目录，然后打开sources.list，把下面的复制进去，具体命令：

cd /etc/apt

sudo gedit sources.list

可能有时候用户想要恢复以前的软件源，然而又没有备份，因此，我把我的电脑ubuntu软件源公开，还只装了少量的软件，软件源基本没有修改过：

# deb cdrom:[Ubuntu 16.04.2 LTS _Xenial Xerus_ - Release amd64 (20170215.2)]/ xenial main restricted# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to# newer versions of the distribution.deb http://cn.archive.ubuntu.com/ubuntu/ xenial main restricted# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial main restricted## Major bug fix updates produced after the final release of the## distribution.deb http://cn.archive.ubuntu.com/ubuntu/ xenial-updates main restricted# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-updates main restricted## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu## team. Also, please note that software in universe WILL NOT receive any## review or updates from the Ubuntu security team.deb http://cn.archive.ubuntu.com/ubuntu/ xenial universe# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial universedeb http://cn.archive.ubuntu.com/ubuntu/ xenial-updates universe# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-updates universe## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team, and may not be under a free licence. Please satisfy yourself as to ## your rights to use the software. Also, please note that software in ## multiverse WILL NOT receive any review or updates from the Ubuntu## security team.deb http://cn.archive.ubuntu.com/ubuntu/ xenial multiverse# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial multiversedeb http://cn.archive.ubuntu.com/ubuntu/ xenial-updates multiverse# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-updates multiverse## N.B. software from this repository may not have been tested as## extensively as that contained in the main release, although it includes## newer versions of some applications which may provide useful features.## Also, please note that software in backports WILL NOT receive any review## or updates from the Ubuntu security team.deb http://cn.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse## Uncomment the following two lines to add software from Canonical's## 'partner' repository.## This software is not part of Ubuntu, but is offered by Canonical and the## respective vendors as a service to Ubuntu users.# deb http://archive.canonical.com/ubuntu xenial partner# deb-src http://archive.canonical.com/ubuntu xenial partnerdeb http://security.ubuntu.com/ubuntu xenial-security main restricted# deb-src http://security.ubuntu.com/ubuntu xenial-security main restricteddeb http://security.ubuntu.com/ubuntu xenial-security universe# deb-src http://security.ubuntu.com/ubuntu xenial-security universedeb http://security.ubuntu.com/ubuntu xenial-security multiverse# deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse