ubuntu apt-get安装软件报错 (You must put some ‘source’ URIs in your sources.list)解决方法

问题：
安装软件时报一下错误：
ubuntu apt-get (You must put some ‘source’ URIs in your sources.list)
E: You must put some ‘source’ URIs in your sources.list

解决方法：

这是因为apt-get找不到一些软件源的url导致的。

1.输入命令：gedit /etc/apt/sources.list

2.复制以下内容到编辑器中，然后保存退出

deb-src http://archive.ubuntu.com/ubuntu trusty main restricted #Added by software-properties
deb-src http://gb.archive.ubuntu.com/ubuntu/ trusty restricted main universe multiverse #Added by software-properties
deb-src http://gb.archive.ubuntu.com/ubuntu/ trusty-updates restricted main universe multiverse #Added by software-properties
deb-src http://gb.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse #Added by software-properties
deb-src http://security.ubuntu.com/ubuntu trusty-security restricted main universe multiverse #Added by software-properties
deb-src http://gb.archive.ubuntu.com/ubuntu/ trusty-proposed restricted main universe multiverse #Added by software-properties

3.执行命令sudo apt-get update

4.之后便可以成功下载软件