环境说明： 设备：树莓派4B 操作系统：ubuntu server20.04
树莓派4B安装的ubuntu要用的是ubuntu-ports的源，而不是原ubuntu的源，若使用错误的源，则在更新时会报错误。
1. 首先备份源文件：
代码语言：javascript复制sudo cp /etc/apt/sources.list /etc/apt/sources.listbak当然备份这一步是可选的，我一般不会备份（因为懒），在修改源文件时注释掉原来的源信息，有问题时去掉注释即可恢复回来
2. 用nano编辑 /etc/apt/sources.list：
代码语言：javascript复制sudo nano /etc/apt/sources.list下面的内容包含了科大的源和阿里云的源，任选一个粘贴到刚打开的文件中，原文件中的内容可以选择注释掉或者删除
代码语言：javascript复制# 科大的源：
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
# 阿里云的源：
deb http://mirrors.aliyun.com/ubuntu-ports focal main restricted
deb http://mirrors.aliyun.com/ubuntu-ports focal-updates main restricted
deb http://mirrors.aliyun.com/ubuntu-ports focal universe
deb http://mirrors.aliyun.com/ubuntu-ports focal-updates universe
deb http://mirrors.aliyun.com/ubuntu-ports focal multiverse
deb http://mirrors.aliyun.com/ubuntu-ports focal-updates multiverse
deb http://mirrors.aliyun.com/ubuntu-ports focal-backports main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu-ports focal-security main restricted
deb http://mirrors.aliyun.com/ubuntu-ports focal-security universe
deb http://mirrors.aliyun.com/ubuntu-ports focal-security multiverse然后ctrl o保存，ctrl x退出
2. 更新源即可：
代码语言：javascript复制sudo apt update
sudo apt upgrade附科大源链接：http://mirrors.ustc.edu.cn/help/ubuntu-ports.html
