[jetson]jetpack5.1的ubuntu20.04更换为清华源

为使后续下载安装顺利，需要给 Ubuntu 系统进行换源

Ctrl + Alt + T 打开终端，输入如下命令

sudo gedit /etc/apt/sources.list

删除原文件内容，添加如下清华源，这里ubuntu版本为20.04，对应如下（或者其他：阿里云源，中科大源）
建议从清华源官方网站找到ubuntu 镜像进行替换。
https://mirrors.tuna.tsinghua.edu.cn/help/ubuntu/

# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse

# deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse
# # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse
# deb-src http://security.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse

# 预发布软件源，不建议启用
# deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse
# # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse

保存（Ctrl + S）并退出（Ctrl + Q）sources.list 文件

进行更新，在终端中输入如下命令

sudo apt-get update