Month: April 2015

Link: Running Android on Desktop: Which Emulator is the Best?

Android is one of the most popular mobile computing operating systems and powers a diverse range of phones, including the low-end ones and the high-end flagship. The good thing about Android is that other than running it on mobile devices, it can also run on the desktop with a suitable emulator. In case you have an ancient Windows machine and want to convert it into something useful, running Android on it can give your ancient Windows machine a new lease of life.

There are many free Android emulators for Windows on the market but only a few of them could match up to our expectations. Listed below is a carefully curated list of Android emulators for your Windows PC.

Full article here:
Running Android on Desktop: Which Emulator is the Best? (Make Tech Easier)

Link: How to set up NTP server in CentOS

Network Time Protocol (NTP) is used to synchronize system clocks of different hosts over network. All managed hosts can synchronize their time with a designated time server called an NTP server. An NTP server on the other hand synchronizes its own time with any public NTP server, or any server of your choice. The system clocks of all NTP-managed devices are synchronized to the millisecond precision.

In a corporate environment, if they do not want to open up their firewall for NTP traffic, it is necessary to set up in-house NTP server, and let employees use the internal server as opposed to public NTP servers. In this tutorial, we will describe how to configure a CentOS system as an NTP server. Before going into the detail, let’s go over the concept of NTP first.

Full article here:
How to set up NTP server in CentOS (Xmodulo)

Link: What the Raspberry Pi 2’s Overclock Settings Mean

The Raspberry Pi 2 is a lot faster than its predecessors, but you still might want to overclock it for the best possible performance. Blogger Hayden James breaks down what each overclock setting does and shares some configurations for better performance.

Full article here:
What the Raspberry Pi 2’s Overclock Settings Mean (Lifehacker)

Link: Access Google Authenticator on the Desktop

No longer are you limited to using your smartphone to use Google’s two-step authentication. There are many apps that you can use easily on your desktop to help keep your accounts more secure.

Keep in mind, though, that using a two-step authenticator app is less secure on your computer. Anyone who has access to your desktop can get your security key and log into your account. But if you don’t own a smartphone, using a program on your computer is better than nothing.

To use any of these apps to secure your accounts, you need to make sure you go through the usual process to enable two-factor authentication on Google or activate any other services that need two-factor authentication. Instead of entering the key into a mobile app, all you do is to enter it on your desktop.

Full article here:
Access Google Authenticator on the Desktop (Make Tech Easier)

Link: How to Install and Configure NTP (Network Time Protocol) Server/Client in Debian Linux

Network Time Protocol (NTP) presents an unique ability for companies to synchronize the clocks of all the systems within the company. Time synchronization is important for many reasons ranging from application time stamps to security to proper log entries. When an organization’s systems all maintain different clock times, it becomes very difficult from a troubleshooting standpoint to determine when and under what conditions a particular event might be occurring.

NTP provides an easy way to ensure that all systems will maintain the correct time which in turn can greatly simplify the burden on administrators/tech support.

Full article here:
How to Install and Configure NTP (Network Time Protocol) Server/Client in Debian Linux(Tecmint)

Link: DD Utility – Easily Backup and Restore Disk Image Files In Ubuntu

The legacy DD is a command line utility for UNIX like operating systems. DD stands for Data Description and the utility empowers the user to copy and convert files but it is a command line utility without any Graphical User Interface (GUI). DD utility can copy and convert simple files, device drivers (e.g for CD ROM, LAN, Speakers, HDD etc) and can access boot sector information that is why it can be used to prepare bootable backup and restore images. It performs the conversions to and from ASCII to EBCDIC, furthermore, it performs the byte order swapping as well. The name of the utility i.e DD seems to have been extracted from IBM’s Job Control Language (JCL) where it appears in a number of command statements.

This article is about a variant of DD command line utility with Graphical User Interface (GUI) i.e dd Utility. It is partially cross platform that is it works on UNIX like operating  Linux Ubuntu and Apple’s Mac OS X.

Full article here:
DD Utility – Easily Backup and Restore Disk Image Files In Ubuntu (LinOxide)

Link: Sed – An Introduction and Tutorial by Bruce Barnett

How to use sed, a special editor for modifying files automatically. If you want to write a program to make changes in a file, sed is the tool to use.

There are a few programs that are the real workhorse in the UNIX toolbox. These programs are simple to use for simple applications, yet have a rich set of commands for performing complex actions. Don’t let the complex potential of a program keep you from making use of the simpler aspects. I’ll start with the simple concepts and introduce the advanced topics later on.

Full article here:
Sed – An Introduction and Tutorial (Grymoire)

Link: 5 Scribd Alternatives to Host Your PDF Files

As you probably know, Scribd is a popular document-hosting website, and if someone wanted to share a PDF file online, chances are they would upload it on Scribd. However, its interface and restrictive features, like paywall and required sign-up to download files, have been making a lot of people unhappy. Since Scribd is modifying its business model to become a “Netflix for books,” maybe it’s time to consider some Scribd alternatives. Luckily, there are more than enough to choose from. Some are simple and offer only basic file upload, while others provide a complete PDF hosting and reading experience.

Full article here:
5 Scribd Alternatives to Host Your PDF Files (Make Tech Easier)

Link: OpenVPN-Setup: Shell script to set up Raspberry Pi (TM) as an OpenVPN server

About

Shell script to set up Raspberry Pi (TM) as a VPN server using the free, open-source OpenVPN software. Includes templates of the necessary configuration files for easy editing, as well as a script for easily generating client .ovpn profiles after setting up the server. Based on the ReadWrite tutorial ‘Building A Raspberry Pi VPN’ by Lauren Orsini (see sources 1 and 2 at the bottom of this Readme).

To follow this guide, you will need to have a Raspberry Pi Model B or later (so long as it has an ethernet port), an SD or microSD card (depending on the model) with Raspbian installed, a power adapter appropriate to the power needs of your model, and an ethernet cable to connect your Pi to your router or gateway. You will also need to setup your Pi with a static IP address (see either source 3 or 4) and have your router forward port 1194 (varies by model & manufacturer; consult your router manufacturer’s documentation to do this). You should also find your Pi’s local IP address on your network and the public IP address of your network and write them down before beginning. Enabling SSH on your Pi is also highly recommended, so that you can run a very compact headless server without a monitor or keyboard and be able to access it even more conveniently (This is also covered by source 4). And last but not least, be sure to change your user password from the default.

Full documentation and download here:
OpenVPN-Setup (GitHub)
Discussion in this Reddit thread

Stop SOME SipVicious attacks from reaching your Asterisk, FreeSwitch, YATE, etc. PBX server

This tip was posted by user “infotek” on the FreePBX site but applies to all software PBX systems that use the iptables firewall. “infotek” wrote:

By default the SipVicious scanner uses the ua : “friendly-scanner”. To block this ua, you can have iptables search the packet for that text.

add the following line to /etc/sysconfig/iptables

-A INPUT -p udp -m udp –dport 5060 -m string –string “friendly-scanner” –algo bm –to 500 -j DROP

Now the thing to keep in mind about this is that it only works if you know the string that will be sent as the user agent, and some hackers using SipVicious may take the trouble to change that default string, but some protection is better than none.  However this same technique can be used to block any attack that constantly sends the same string as the user agent, if you know what that string contains.

For those that use Webmin to manage iptables, here are the settings to use.  This should come BEFORE any other rules applicable to port 5060 – I made it the very first rule on the page “Incoming packets (INPUT) – Only applies to packets addressed to this host“:

Rule comment: Stop SipVicious
Action to take: Drop
Network protocol: Equals UDP
Destination TCP or UDP port: Equals Port(s) 5060
Additional IPtables modules: string
Additional parameters: –string “friendly-scanner” –algo bm –to 500

All other settings on the Webmin “Add Rule” page should be left at the default value (usually <ignored>).

To stop the hackers clever enough to change the default user agent string, consider also using this technique.

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