前言
在嵌入式开发中，常用到ARM64的开发平台，进行下载东西时想换国内源，下面以中科大源为参考
一、什么是源？
其实吧它就像苹果和案桌的软件应用商店一样，为Linux用户提供软件下载及更新服务的。
Linux家族有三个软件源系统：
yum源，使用这种软件管理器的主要是：RedHat，CentOS
apt源，使用这种软件管理器的主要是：Ubuntu
Pacman源，使用这种软件管理器的主要是：archlinux还有新近崛起的Manjaro
Ubuntu是外国人开发的系统，默认使用的也是国外的源，但是从国内翻^qiang下载国外的软件（插件）源太慢。其实国内也有很多的镜像源，比如说阿里源，网易源，清华园（源），中科大源（推荐，不限速），兰州大源。
————————————————
二、使用步骤
1.备份源文件
sudo cp /etc/apt/sources.list sources_backup.list
2.修改文件
sudo vim /etc/apt/sources.list
删除原有的内容，添加以下：
# 默认注释了源码仓库，如有需要可自行取消注释
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
# 预发布软件源，不建议启用
# deb https://mirrors.ustc.edu.cn/ubuntu-ports/ focal-proposed main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu-ports/ focal-proposed main restricted universe multiverse
如要用于其他版本，把 focal 换成其他版本代号即可: 22.04：jammy；20.04：focal；18.04：bionic；16.04：xenial；14.04：trusty。
3、更新配置
sudo apt-get update
sudo apt-get upgrade
其他源
清华源：
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
163源
deb http://mirrors.163.com/ubuntu/ bionic main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ bionic-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ bionic-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ bionic-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ bionic main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ bionic-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ bionic-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ bionic-backports main restricted universe multiverse
