树莓派4 国内源

sudo apt install leafpad(   "_*  I prefer to use it)

sudo leafpad /etc/apt/sources.list

deb https://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ buster main contrib non-free rpi

& another one:

leafpad  /etc/apt/sources.list.d/raspi.list

deb https://mirrors.tuna.tsinghua.edu.cn/raspberrypi/ buster main

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If you only change one,sometimes you will get update erro.