因为众所周知的原因，Linux默认的apt源在国内神慢……换吧

1.改sources.list

sudo vim /etc/apt/sources.list

内容全部改为

deb http://mirrors.ustc.edu.cn/raspbian/raspbian/ buster main contrib non-free rpi
#deb-src http://mirrors.ustc.edu.cn/raspbian/raspbian/ buster main contrib non-free rpi

2.改raspi.list

sudo vim /etc/apt/sources.list.d/raspi.list

内容全部改为

deb http://mirrors.ustc.edu.cn/archive.raspberrypi.org/debian/ buster main ui
deb-src http://mirrors.ustc.edu.cn/archive.raspberrypi.org/debian/ buster main ui

爽快！