目录

1.编辑sources.list文件

2.复制粘贴正确的软件源

3.更新软件源和软件

4. ubuntu mate 20.04

1.编辑sources.list文件

首先，将原有的sources.list内容删掉，用vim打开sources.list文件

sudo vim /etc/apt/sources.list

然后dG删除全部内容，然后按i编辑文件.

2.复制粘贴正确的软件源

ubuntu mate 16.04的将以下内容粘贴进去：

## Note, this file is written by cloud-init on first boot of an instance 
## modifications made here will not survive a re-bundle. 
## if you wish to make changes you can: 
## a.) add 'apt_preserve_sources_list: true' to /etc/cloud/cloud.cfg 
##     or do the same in user-data 
## b.) add sources in /etc/apt/sources.list.d 
## c.) make changes to template file /etc/cloud/templates/sources.list.tmpl# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to 
# newer versions of the distribution. 
deb http://mirrors.ustc.edu.cn/ubuntu-ports xenial main restricted 
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports xenial main restricted## Major bug fix updates produced after the final release of the 
## distribution. 
deb http://mirrors.ustc.edu.cn/ubuntu-ports xenial-updates main restricted 
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports 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://mirrors.ustc.edu.cn/ubuntu-ports xenial universe 
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports xenial universe 
deb http://mirrors.ustc.edu.cn/ubuntu-ports xenial-updates universe 
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports 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://mirrors.ustc.edu.cn/ubuntu-ports xenial multiverse 
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports xenial multiverse 
deb http://mirrors.ustc.edu.cn/ubuntu-ports xenial-updates multiverse 
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports 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://mirrors.ustc.edu.cn/ubuntu-ports xenial-backports main restricted universe multiverse 
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports xenial-backports main restricted universe multiverse deb http://mirrors.ustc.edu.cn/ubuntu-ports xenial-security main restricted 
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports xenial-security main restricted 
deb http://mirrors.ustc.edu.cn/ubuntu-ports xenial-security universe 
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports xenial-security universe 
deb http://mirrors.ustc.edu.cn/ubuntu-ports xenial-security multiverse 
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports xenial-security 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

然后esc退出编辑，:wq保存退出。

3.更新软件源和软件

sudo apt update
sudo apt upgrade

4. ubuntu mate 20.04

ubuntu mate 20.04的将以下内容粘贴进去：

deb https://mirrors.ustc.edu.cn/ubuntu-ports/ focal main restricted universe multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu-ports/ focal main main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu-ports/ focal-updates main restricted universe multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu-ports/ focal-updates main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu-ports/ focal-backports main restricted universe multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu-ports/ focal-backports main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu-ports/ focal-security main restricted universe multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu-ports/ focal-security main restricted universe multiverse

如果出现了如下报错：

 则将https链接改成http链接即可，这个是因为https是加密链接，需要安全证书，终端提示未发现服务器安全协议。