一、首先是安装清华源，按照网上的教程来在官网安装（base 树莓派）：
- 首先确定系统版本：
more /etc/debian_version
- 然后根据系统版本来跑上面给的指令：
# armv7l 用户：编辑 `/etc/apt/sources.list` 文件，删除原文件所有内容，用以下内容取代
deb http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ buster main non-free contrib rpi
# deb-src http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ buster main non-free contrib rpi
# armv7l 用户如果需要开启 multi-arch 使用 arm64 软件源，需要在 `/etc/apt/sources.list` 中加上
deb [arch=arm64] http://mirrors.tuna.tsinghua.edu.cn/raspbian/multiarch/ buster main
# aarch64 用户：编辑 `/etc/apt/sources.list` 文件，用以下内容取代：
# 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/debian/ buster main contrib non-free
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ buster main contrib non-free
deb https://mirrors.tuna.tsinghua.edu.cn/debian/ buster-updates main contrib non-free
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ buster-updates main contrib non-free
deb https://mirrors.tuna.tsinghua.edu.cn/debian/ buster-backports main contrib non-free
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ buster-backports main contrib non-free
deb https://mirrors.tuna.tsinghua.edu.cn/debian-security buster/updates main contrib non-free
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian-security buster/updates main contrib non-free
# 对于两个架构，编辑 `/etc/apt/sources.list.d/raspi.list` 文件，删除原文件所有内容，用以下内容取代：
deb http://mirrors.tuna.tsinghua.edu.cn/raspberrypi/ buster main
二、更新软件源
在执行sudo apt-get update后出现以下的问题：
Reading package lists… Done
W: GPG error: http://mirrors.tuna.tsinghua.edu.cn/raspbian/multiarch bullseye InRelease: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY E77FC0EC34276B4B
E: The repository ‘http://mirrors.tuna.tsinghua.edu.cn/raspbian/multiarch bullseye InRelease’ is not signed.
N: Updating from such a repository can’t be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details
The following signatures couldn’t be verified because the public key
is not available: NO_PUBKEY E77FCOEC34276B4B Reading package lists…
Done W: GPG error: http://mirrors. tuna. ts inghua. edu.
cn/raspbian/multiarch bullseye InRelease: The following signatures co
uldn’t be verified because the public key is not available: NO_PUBKEY
E77FCOEC34276B4B E: The repository ’ http://mirrors. tuna. ts inghua.
edu. cn/raspb ian/multiarch bullseye InRelease’ is not signed. N:
Updat ing from such a repository can’t be done securely, and is
therefore disabled by default. N: See apt-secure(8) manpage for
repository creation and user configuration details.
三、解决办法：
更换源之后需要添加公钥，执行以下命令：
- 注意：这里的recv-keys就是报错中的key，粘贴过来即可：
gpg --keyserver keyserver.ubuntu.com --recv-keys E77FC0EC34276B4B
gpg --export --armor E77FC0EC34276B4B | sudo apt-key add -