错误信息

sudo apt-get install -y apt-transport-https ca-certificates curl software-properties-common

Reading package lists… Done

Building dependency tree

Reading state information… Done

apt-transport-https is already the newest version (1.6.12ubuntu0.1).

ca-certificates is already the newest version (20190110ubuntu1).

curl is already the newest version (7.68.0-1ubuntu2).

Some packages could not be installed. This may mean that you have

requested an impossible situation or if you are using the unstable

distribution that some required packages have not yet been created

or been moved out of Incoming.

The following information may help to resolve the situation:

The following packages have unmet dependencies:

software-properties-common : Depends: python3-software-properties (= 0.96.24.32.13) but it is not going to be installed

E: Unable to correct problems, you have held broken packages.

方案

Ubuntu 的软件源配置文件是 /etc/apt/sources.list。将系统自带的该文件做个备份，将该文件替换为下面内容，即可使用 TUNA 的软件源镜像。

90%是因为源配错了

https://mirrors.tuna.tsinghua.edu.cn/help/ubuntu/

选择需要的源（一定要根本版本来）



查看 Ubuntu的版本

输入命令
lsb_release -a
显示如下
Distributor ID: Ubuntu                           //类别是ubuntu
Description:  Ubuntu 16.04.3 LTS          //16年3月发布的稳定版本，LTS是Long Term Support：长时间支持版本，支持周期长达三至五年
Release:    16.04                                    //发行日期或者是发行版本号
Codename:   xenial                               //ubuntu的代号名称

修改后运行

sudo apt-get update

即可！！！