Why port 80 (HTTP) reported as open by nmap when it is closed?

Posted on in Categories Security last updated July 2, 2017

Why are some ports reported as open by nmap?
I recently setup a small server which is running Debian 9. The purpose of this machine is to run OpenVPN server on port 443 to bypass censorship. It runs the following services and nothing else:

  1. Squid on private IP belongs to VPN pool (10.8.0.1:3128)
  2. SSH on private IP belongs to VPN pool (10.8.0.1:22)
  3. DNS resolver on private IP belongs to VPN pool (10.8.0.1:53)
  4. OpneVPN on public IP port 443 (server_public_ip_address:443)

Download of The Day: Debian Linux 9 ( Stretch )

Posted on in Categories Linux News last updated June 18, 2017

Debian GNU/Linux version 9.0 stretch has been released ( jump to download ) after many months of constant development and available for download in various media format. Debian 9.0 is a free operating system includes various new features such as support for mips64el architecture, GNOME 3.22, KDE Plasma 5.8, LXDE, LXQt 0.11, MATE 1.16, Xfce 4.12, Linux kernel 4.9 and more. Debian 9 is dedicated to the project’s founder Ian Murdock, who passed away on 28 December 2015.
Debian 8.x 64-bit-mate-desktop-screenshot

How to use parallel ssh (PSSH) for executing ssh in parallel on a number of Linux/Unix/BSD servers

Posted on in Categories Cloud Computing, Command Line Hacks, Howto last updated April 21, 2017

Recently I come across a nice little nifty tool called pssh to run a single command on multiple Linux / UNIX / BSD servers. You can easily increase your productivy with this SSH tool.

More about pssh

pssh is a command line tool for executing ssh in parallel on some hosts. It provides specialties includes:

  1. Sending input to all of the processes
  2. Inputting a password to ssh
  3. Saving output to files
  4. IT/sysadmin taks automation such as patching servers
  5. Timing out and more

Let us see how to install and use pssh on Linux and Unix-like system.

pssh-welcome

How to protects Linux and Unix machines from accidental shutdowns/reboots with molly-guard

Posted on in Categories Command Line Hacks, Debian Linux, Hardware last updated February 19, 2017

Oops! I did it again. I thought I was logged into my home server. Turns out I rebooted the db server. Another my not so favorite is typing “shutdown -h 0” into the wrong terminal. I know a few people who have admitted to doing that here.

My anger that can't be contained
Is there any end to the madness? Do I need to suffer from accidentally random reboots and shutdowns? After all, it is human nature to make mistakes, but one should not keep on making the same mistakes again and again.

How to use CoreFreq CPU monitoring software on Linux

Posted on in Categories Hardware, Open Source last updated February 8, 2017

Recently I came across an excellent software called CoreFreq. It is a CPU monitoring software designed for 64-bits Processors w/ architectures Intel Atom, Core2, Nehalem, SandyBridge and superior, and AMD Family 0F. It runs on 64 bit Linux system. CoreFreq provides a framework to retrieve CPU data with a high degree of precision: