树莓派3b+ ubuntu镜像配置国内软件源

默认选择清华镜像https://mirrors.tuna.tsinghua.edu.cn/help/ubuntu/

要注意网站说明：

Ubuntu 镜像使用帮助

本镜像仅包含 32/64 位 x86 架构处理器的软件包，在 ARM(arm64, armhf)、PowerPC(ppc64el)、RISC-V(riscv64) 和 S390x 等架构的设备上（对应官方源为ports.ubuntu.com）请使用 ubuntu-ports 镜像。

但是要注意，arm架构要更换为这样，否则apt-get upgrade时会报404：

# 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-ports/ jammy main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ jammy main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ jammy-updates main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ jammy-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ jammy-backports main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ jammy-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ jammy-security main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ jammy-security main restricted universe multiverse

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