1.输入该命令按回车键:cd /etc/apt
2.mv sources.list sources.list.back,输入该命令按回车键
3.输入该命令按回车键:vi sources.list
4.按“i”进入插入模式,输入以下内容,然后按“ESC”键输入wq按回车键保存退出vi编辑
deb http://archive.debian.org/debian stretch main
deb-src http://archive.debian.org/debian stretch main
deb http://archive.debian.org/debian-security stretch/updates main
deb-src http://archive.debian.org/debian-security stretch/updates main
5.输入该命令按回车键可以正常执行:apt-get update -y