如国内网络使用ubuntu 则会出现apt-get无法安装更新的问题，这时大家需要切换到一些国内第三方更新源。
- 首先查看自己的ubuntu系统的codename，直接导致你更新的源是否对你的系统起效果，查看方法： lsb_release -a
我的系统显示：Codename: bionic 确认阿里源支持
登陆以下网页：http://mirrors.aliyun.com/ubuntu/dists/
该网页显示了阿里云支持的ubuntu系统下各个Codename版本，确保自己的Codename在该网页中存在（一般都会有的）备份系统源：
cd /etc/apt
sudo mv sources.list sources.list_bak添加新的源文件：sudo vi sources.list
并添加以下内容：注意，每一行的trusty应该用第一步查看得到的Codename来代替
deb http://mirrors.aliyun.com/ubuntu/ trusty main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ trusty-backports main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ trusty-proposed main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ trusty-security main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu/ trusty-updates main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ trusty main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-backports main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-proposed main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-security main multiverse restricted universe
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-updates main multiverse restricted universe保存并且sudo apt-get update，更新成功
