How to enable Wake on Lan (WOL) with Advanced TomatoUSB wifi router firmware

Posted on in Categories Hardware, Howto, Networking, Open Source last updated March 29, 2017

I recently installed TomatoUSB advanced firmware on my Asus RT-AC66U wifi router. This router act as my wireless Ethernet bridge. TomatoUSB advanced has additional features like

  • SSH
  • Multiple WAN support (3G/4G/Static IP/Cable/ADSL2)
  • Tor
  • Virtual Wireless
  • DMZ
  • IPv6
  • FTP/Media server via USB
  • BiTorrent Client via USB
  • UPS support
  • OpenVPN client and server
  • Tinc VPN server and much more.

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 speed up OpenSSL/GnuPG Entropy For Random Number Generation On Linux

Posted on in Categories Howto, Open Source, Security last updated November 7, 2016

Entropy is nothing but the measure of “randomness” in a sequence of bits. The PRNG ( pseudorandom number generator ) is a special device (e.g. /dev/random on Linux) to create randomness from server hardware activities. It uses interrupts generated from the keyboard, hard disk, mouse, network and other sources. The random number generator gathers environmental noise from device drivers and other sources into an entropy pool. The randomness usually used for security purposes like creating TLS/SSL keys and the quality source of random bits is critical. For example, OpenSSL APIs can use quality randomness to make your program cryptographically secure. However, a poor source of randomness could result in loss of security. In this post, I will cover haveged and rng-utils/rng-tools to generate random numbers and feed linux random device for your virtual or dedicated Linux server.

Disabling Google Chrome PDF viewer

Posted on in Categories Howto last updated August 29, 2016

Google Chrome has “Chrome PDF Viewer” to view or open pdf files. It is an unwanted feature. I do not need it at all. I want my PDF open in Preview on a MacOS X or default pdf viewer in Linux. This feature was hidden. I want to disable it from my Google Chrome browser because it was slow scrolling with a large pdf file sizes.

Accessing Internet from cloud VM when you have only private network enabled

Posted on in Categories Hardware, Howto last updated August 17, 2016

We have a couple of virtual servers hosted with Softlayer for processing data and backup purpose. The public interface is completely turned off i.e. no Internet access. We can only access VMs using a VPN. It resulted in decreased costs and many security problems for backend servers. However, when you order “Private Network Only” cloud VM, you cannot route outgoing traffic to the Internet using your VM.