由于国内使用官方源导致下载速度慢等各方面原因，很多人将官方源替换成阿里源等，但是某些应用安装会报错。现将官方源分享如下：
备份当前源：
执行命令：#
sudo cp /etc/apt/sources.list /etc/apt/sources.list.back
编辑恢复源：
执行命令：# sudo gedit /etc/apt/source.list #推荐使用gedit比较方便复制粘贴，最好获取root权限，不然可能会出现保存错误。
Ubuntu官方源：
#deb cdrom:[Ubuntu 16.04.3 LTS _Xenial Xerus_ - Release amd64 (20170801)]/ xenial main restricted # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://us.archive.ubuntu.com/ubuntu/ xenial main restricted # deb-src http://us.archive.ubuntu.com/ubuntu/ xenial main restricted ## Major bug fix updates produced after the final release of the ## distribution. deb http://us.archive.ubuntu.com/ubuntu/ xenial-updates main restricted # deb-src http://us.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://us.archive.ubuntu.com/ubuntu/ xenial universe # deb-src http://us.archive.ubuntu.com/ubuntu/ xenial universe deb http://us.archive.ubuntu.com/ubuntu/ xenial-updates universe # deb-src http://us.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://us.archive.ubuntu.com/ubuntu/ xenial multiverse # deb-src http://us.archive.ubuntu.com/ubuntu/ xenial multiverse deb http://us.archive.ubuntu.com/ubuntu/ xenial-updates multiverse # deb-src http://us.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://us.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse # deb-src http://us.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 partner deb http://security.ubuntu.com/ubuntu xenial-security main restricted # deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted deb http://security.ubuntu.com/ubuntu xenial-security universe # deb-src http://security.ubuntu.com/ubuntu xenial-security universe deb http://security.ubuntu.com/ubuntu xenial-security multiverse # deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse