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