Easy steps to share an external USB drive on your Raspberry Pi

 Refer the whole story published on Medium

LINK --> My story on Medium

Setting up Pi-Hole with OpenDNS (Stop Ads and Get Content Filtering) at home

Below is described how to setup pi-hole and OpenDNS at home. I used Raspberry Pi 3 for it and the below tutorial will describe all the steps pertaining to it only. Refer to the end of the blog for additional help.

Prerequisite:

• Raspberry Pi (3 or above) with Raspbian installed and SSH ready. (Refer References section below for help with it. I will call Raspberry Pi as the pi machine henceforth).
• A router supporting custom DHCP configuration (I am going to explain for Netgear Router).
• Computer to SSH the pi machine (Mac or PC) (I used Mac in this tutorial. You can skip this and do it directly on the pi machine if you have set it up with keyboard and monitor).
• Internet
• Lots of spare time. (This is very important)

 Step1: Install pi-hole on Raspberry Pi

 * Before you begin, ensure that the pi machine is connected to the internet.

• Open Terminal and SSH to the raspberry pi using the command below:

ssh user@pihostname.local

Replace user and pihostname with the user and hostname you have configured for your pi machine.

• On the terminal, type the below commands to install pi-hole. 

          * Before you begin: 

• Use all the default configurations as shown by the installer do not change it (We will change it later using the pi-hole console).

• The installer will ask you to install a webserver to install the pi-hole console. This is an optional step but go ahead with installing it as we need this console later for changing settings of pi-hole.

• Ensure that you do not have another web server on your pi machine. If you have it then the pi-hole console will not come up. So, it is better to stop the server before starting. 

• After the installation note the following:
• IPv4 address of the pi machine.
• IPv6 address of the pi machine.
• The password of the pi-hole console given.

git clone --depth 1 https://github.com/pi-hole/pi-hole.git Pi-hole

cd "Pi-hole/automated install/"

sudo bash basic-install.sh

For other ways to install pi-hole refer to this documentation: https://github.com/pi-hole/pi-hole/#alternative-install-methods

Step2: Configure the pi machine as the DHCP server on Router.

*Before you start, note:

1. The configuration below is only for Netgear routers. For other routers, refer to the router manual.
2. Ensure Parental Settings are turned off. (Don't worry as after OpenDNS configuration those will get auto applied)

• Go to router admin settings. On Netgear routers, it can be opened in a browser by typing the following URL and entering the admin user password you used while setting up your router. If you did not configure the new admin password then it can be found on your router or in the user manual.

          http://routerlogin.net (Ensure that you are connected to your home wifi before opening the URL)

• Change Domain Name Server (DNS) Address settings

• Go to Advanced -> Setup -> Internet Setup
• On the right pane, enter the IPv4 address of the pi machine you noted in Step 1 as Primary DNS after selecting the "Use These DNS Servers" option.

• Apply the settings (This will restart the router)

• Change IPv6 settings

• After router is restarted, go to Advanced -> Advanced Setup -> IPv6
• Select "Use DHCP Server"
• Enter the IPv6 address of the pi machine in "Start Address" field
• Select "Use These DNS Servers" option.
• Enter the IPv6 address of the pi machine in "Primary DNS" fields.
• Apply the settings (This will restart the router)

Step3: Open the pi-hole console and configure OpenDNS

• Open the browser on the computer from which you are doing SSH and enter the following URL
  
  http://pi.hole/admin/index.php?login
  or
  http://<Ip address of pi machine>/admin/index.php?login

          Pi-console will be shown as below:

• Enter the password noted in Step 1 and go to Dashboard. The screen will look as shown below

• Go to Settings -> DNS and do the following:

• Uncheck any checkbox under settings "Upstream DNS Servers" on the left side.
• Under "Upstream DNS Servers" on the right side check all the checkboxes and enter the following information:
• Under Custom 1 (IPv4) enter: 208.67.222.123
• Under Custom 2 (IPv4) enter: 208.67.220.123

*Note: Refer IP Addresses at https://docs.pi-hole.net/guides/upstream-dns-providers/ under the OpenDNS section if the above IP address does not work. I chose IP Address with Family Filters (IPv6 server is not present currently).

• After entering the information scroll to the bottom of the page and press the "SAVE" button.

• After you save the information, the screen will look as shown below.

If you have done everything as described above then you are all set. This not only removes ads from all the apps (on phones) but from all the sites your surf. Plus, you get content filtering from OpenDNS (restricted access to porn, malware, unfriendly sites, etc).

References:

• https://projects.raspberrypi.org/en/projects/raspberry-pi-setting-up (Setup Raspberry Pi)
• https://magpi.raspberrypi.org/articles/ssh-remote-control-raspberry-pi (Setup SSH on Raspberry Pi)
• https://pi-hole.net
• https://github.com/pi-hole/pi-hole/#alternative-install-methods
• https://discourse.pi-hole.net/t/how-do-i-configure-my-devices-to-use-pi-hole-as-their-dns-server/245
• https://docs.pi-hole.net/guides/upstream-dns-providers/
• https://discourse.pi-hole.net/t/using-netgear-nighthawk-ac1900-r7000-router-with-opendns-parental-controls-plus-pi-hole/9274/2

Cohesion and Coupling and their types

Stumbled upon an article: http://www.infoworld.com/article/2949579/application-architecture/design-for-change-coupling-and-cohesion-in-object-oriented-systems.html

Following are the details from the article which are most important:

 

Coupling

Coupling may be defined as the degree of interdependence that exists between software modules and how closely they are connected to each other. In essence, coupling indicates the strength of interconnectedness between software modules. When this coupling is high, we may assume that the software modules are interdependent, i.e., they cannot function without the other. There are several dimensions of coupling:

• Content coupling -- this is a type of coupling in which a particular module can access or modify the content of any other module. In essence, when a component passes parameters to control the activity of some other component, there is a control coupling amongst the two components.
• Common coupling -- this is a type of coupling in which you have multiple modules having access to a shared global data
• Stamp coupling -- this is a type of coupling in which data structure is used to pass information from one component in the system to another
• Control coupling -- this is a type of coupling in which one module can change the flow of execution of another module
• Data coupling -- in this type of coupling, two modules interact by exchanging or passing data as a parameter

Cohesion

Cohesion denotes the level of intra-dependency amongst the elements of a software module. In other words, Cohesion is a measure of the degree to which the responsibilities of a single module or a component form a meaningful unit. Cohesion is of the following types:

• Co-incidental cohesion -- this is an unplanned random cohesion that might be a result of breaking a module into smaller modules.
• Logical cohesion -- this is a type of cohesion in which multiple logically related functions or data elements are placed in the same component
• Temporal cohesion -- this is a type of cohesion in which elements of a module are grouped in a manner in which they are processed at the same point of time. An example could be a component that is used to initialize a set of objects.
• Procedural cohesion -- this is a type of cohesion in which the functions in a component are grouped in a way to enable them to be executed sequentially and make them procedurally cohesive
• Communicational cohesion -- in this type of cohesion the elements of a module are logically grouped together in a way that they execute sequentially and they work on the same data
• Sequential cohesion -- in this type of cohesion the elements of a module are grouped in such a manner that the output of one of them becomes the input of the next -- they all execute sequentially. In essence, if the output of one part of a component is the input of another, we say that the component has sequential cohesion.
• Functional cohesion -- this is the best and the most preferred type of cohesion in which the degree of cohesion is the highest. In this type of cohesion, the elements of a module are functionally grouped into a logical unit and they work together as a logical unit -- this also promotes flexibility and reusability.

The best practices

Tight coupling increases the maintenance cost as it is difficult and changes to one component would affect all other components that are connected to it. So, code refactoring becomes difficult as you would need to refactor all other components in the connected-chain so that the functionality doesn't break. This process is cumbersome and takes a lot of tedious effort and time.

You should design classes that contain the less number of instance variables, i.e., your class design is "good" if it contains a small number of instance variables. Ideally, each of the methods in your class should manipulate one or more of these instance variables. Theoretically, a class is maximally cohesive if each of the instance variables of the class is used or manipulated by each of the methods of that class. When cohesion in class is high the methods and the data members of the class are co-dependent and work together as a single logical unit. However, in reality it isn't possible to design such classes or I would rather say, it is not advisable to design classes that are maximally cohesive.

Puzzle Time

Its amazing that in day to day life in office and discussion with colleges churn out some really interesting knowledge bits and these bits sometimes vibrate quite a bit of threads in your head. Here are some of those bits.
  
** River crossing: she-goat, wolf and cabbage 

Description:

A farmer is returning from market, where he bought a she-goat, a wolf and cabbage. On the way home he must cross a river. His boat is little, allowing him to take only one of the three things. He can’t keep the she-goat and the cabbage together (because the she-goat would eat it), nor the she-goat with the wolf (because the she-goat would be eaten). How shall the farmer get everything on the other side (without any harm)?

Solution:

farmer crosses with goat
farmer returns alone
farmer crosses with cabbage or wolf
farmer returns with goat
farmer crosses with whichever (cabbage or wolf) he didn’t take the first time
farmer returns alone
farmer crosses with goat
they are all on the other side

** Four glasses puzzle/ blind bartender's problem (
http://en.wikipedia.org/wiki/Four_glasses_puzzle)

Description: 

Four glasses or tumblers are placed on the corners of a square rotatable table. Some of the glasses are upright (up) and some upside-down (down). A blindfolded person is seated next to the rotatable table and is required to re-arrange the glasses so that they are all up or all down, either arrangement being acceptable, which will be signalled by the ringing of a bell.

The glasses may be re-arranged in turns subject to the following rules:
1. Any two glasses may be inspected in one turn and after feeling their orientation the person may reverse the orientation of either, neither or both glasses.
2. After each turn the table is rotated through a random angle.

The puzzle is to devise an algorithm which allows the blindfolded person to ensure that all glasses have the same orientation (either up or down) in a finite number of turns. The algorithm must be non-stochastic i.e. it must not depend on luck.  

Solution:

An algorithm that guarantees the bell will ring in at most five turns is as follows:

1. On the first turn choose a diagonally opposite pair of glasses and turn both glasses up.
2. On the second turn choose two adjacent glasses. At least one will be up as a result of the previous step. If the other is down, turn it up as well. If the bell does not ring, then there are now three glasses up and one down.
3. On the third turn choose a diagonally opposite pair of glasses. If one is down, turn it up and the bell will ring. If both are up, turn one down. There are now two glasses down, and they must be adjacent.
4. On the fourth turn choose two adjacent glasses and reverse both. If both were in the same orientation then the bell will ring. Otherwise there are now two glasses down and they must be diagonally opposite.
5. On the fifth turn choose a diagonally opposite pair of glasses and reverse both. The bell will ring.

Enabling x86 Android Emulation

We all have experienced slow emulator on Mac, Linux and Windows (especially windows) because of which we use virtualization images of Android i.e. Genymotion, etc. So, if you are running your OS on Intel processor then you can use Intel HAXM (Hardware Acclerated Execution Manager) to speedup your emulator.

Following are the links which discuss as to how to implement HAXM:

For Windows and Linux: http://software.intel.com/en-us/articles/speeding-up-the-android-emulator-on-intel-architecture

For Mac: http://simonguest.com/2013/04/16/enabling-x86-android-emulation/

Does Google Nexus 4 Orange Blinking Light creating lots of tension in your head ???

Hey guys...is Google Nexus 4 blinking orange light giving you jitters and cramps in your head and you have charged it for lots and lots of hours but it is still being the dumb ass and keep doing the same...well then here is the bumper for it to solve its idiotic nature. Here is the 3 steps procedure:

• Step 1: Unplug it if you are still being positive and charging it.
• Step 2: Press and hold Power button.
• Step 3: Plug it by still keeping power button pressed and after 60 seconds leave the button, after 20 min or so you will see the white charging icon and its done...your phone is back from being a dumb ass.

Why this happens ?

There is no one answer but some blogs suggests which i believe is that there is a Deep Hibernation mode for battery in Nexus 4 which leads it to show this dumb behavior and this behavior is triggered if your phone battery goes off and you don't charge it for couple of hours. For me this happens if i leave it for more than 6-8 hours on a discharged battery.

I hope this helps someone who is feeling to suicide because of this behavior of his Nexus 4....but cheers and no need of that. Keep smiling.

Semantic Versioning

Semantic versioning is a simple versioning scheme suggested by OSGi Alliance where it conveys much more meaning about what’s changing than normal versioning schemes do.

Following are the key points:

• Every version consists of four parts: major, minor, micro, and qualifier (Major.Minor.Micro.Qualifier).
  
• A change to the major part of a version number (for example, changing 2.0.0.0 to 3.0.0.0) indicates that the code change isn’t backwards compatible. Removing a method or changing its argument types is an example of this kind of breaking change.
  
• A change to the minor part (for e.g., changing 2.0.0.0 to 2.1.0.0) indicates a change that is backwards compatible for consumers of an API, but not for implementation providers. For example, the minor version should be incremented if a method is added to an interface in the API, because this will require changes to implementations.
  
• If a change doesn’t affect the externals at all, it should be indicated by a change to the micro version (for e.g., changing 2.0.0.0 to 2.0.1.0). Such a change could be a bug fix, or a performance improvement, or even some internal changes that remove a private method from an API class. Having a strong division between bundle internals and bundle externals means the internals can be changed dramatically without anything other than the micro version of the bundle needing to change.
  
• Finally, the qualifier is used to add extra information, such as a build date (for e.g. changing 2.0.0.0 to 2.0.0.110813, 110813 represents 08-Nov-2013) .

Among the version sections defined above, many of the product/component writers prefer Major, Minor and Micro and in some cases even Micro is left back and just add to your general knowledge Google does not follow any (WTH!!). So, its up to you as how you take it. For me, i love it.