系统提示报错：

r8169 0000:03:00.0: firmware: failed to load rtl_nic/rtl8168g-3.fw (-2)

解决方案：

$ sudo gedit /etc/apt/sources.list

添加源：

#realtek firmware
deb http://ftp.de.debian.org/debian stretch main non-free
deb-src  http://ftp.de.debian.org/debian stretch main non-free

安装源：

sudo apt-get update
sudo apt-get install firmware-realtek