如下图所示提示签名无效下载失败，导致更新不了msf
解决办法如下：
echo ‘deb http://apt.metasploit.com/ lucid main‘ > /etc/apt/sources.list.d/metasploit-framework.list
wget -O - http://apt.metasploit.com/metasploit-framework.gpg.key | apt-key add -
apt-get update
msfupdate
原文：https://www.cnblogs.com/websecyw/p/11641603.html