Problem
When you ask some website with https head.you may met the problem secure connection failed firefox browser.
the answer is tool-preferences-Advanced-Certifactes cancel Query OCSP responder servers to confirm the current validity of certificates.
Now you can solve the problem.
Difference between RedHat Ubuntu Debian Kali
I think Linux becomes two Part with some years.popular linuxs.
one part,RedHat , the other Debian.
Introduce Red Hat Linux
红帽企业Linux charge RHEL(Red Hat Enterprise Linux operating system)
RPM(Red hat Package manager)包管理 .rpm
yum（全称为 Yellow dog Updater, Modified)
Introduce Debian
Kali Linux & Ubuntu free forever
dpkg (Debian package manager)
apt (Advanced package tool（Debian或基于Debian的发行版中提供）)
other
.so（扩展名so）：Shared object，dynamically linked library
.o（扩展名o）：Object
file，complied
result of C/C++ source file
tar：Tape archive
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KALI Linux problems & Study Red Hat | Ubuntu
原文：http://www.cnblogs.com/yaochc/p/6037083.html