在树莓派上安装软件时候，经常遇到无法找到软件包或者下载速度过慢等情况，这时候我们需要更换软件源。

1. 首先，打开/etc/apt/sources.list

   sudo nano /etc/apt/sources.list

2. 用#注释掉旧源，方法将

deb http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ stretch main contrib$
deb-src http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ stretch main con$
#deb http://raspbian.raspberrypi.org/raspbian/ stretch main contrib non-free rpi
# Uncomment line below then 'apt-get update' to enable 'apt-get source'
#deb-src http://raspbian.raspberrypi.org/raspbian/ stretch main contrib non-fre$

改为

#deb http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ stretch main contrib$
#deb-src http://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ stretch main con$
#deb http://raspbian.raspberrypi.org/raspbian/ stretch main contrib non-free rpi
# Uncomment line below then 'apt-get update' to enable 'apt-get source'
#deb-src http://raspbian.raspberrypi.org/raspbian/ stretch main contrib non-fre$

3. 更换新源，将如下源任选其一粘贴进去

1.阿里云提供

deb http://mirrors.aliyun.com/raspbian/raspbian/ jessie main contrib non-free rpi
deb-src http://mirrors.aliyun.com/raspbian/raspbian/ jessie main contrib non-free rpi

2.中科大提供

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

4. 更新软件源

   sudo apt-get upgrade