vi /etc/apt/sources.list
把下面这段话复制，加在该文件最下面，保存
deb http://mirrors.163.com/debian lenny main non-free contrib
deb http://mirrors.163.com/debian lenny-proposed-updates main contrib non-free
deb http://mirrors.163.com/debian-security lenny/updates main contrib non-free
deb-src http://mirrors.163.com/debian lenny main non-free contrib
deb-src http://mirrors.163.com/debian lenny-proposed-updates main contrib non-free
deb-src http://mirrors.163.com/debian-security lenny/updates main contrib non-free
输入sudo rm /var/lib/apt/lists/lock 强制把/var/lib/apt/lists/lock删掉。 之后就能apt-get update了
ubuntu 安装 ptf E: Unable to locate package vsftp
原文：https://www.cnblogs.com/donaldworld/p/12310965.html