How to use dd (Linux copy tool) with progress indicator

/dev/sdcdd, the ubiquitous copy tool of Unix/Linux, now comes in with a decent built-in progress indicator.

You can run it by the command-line option: status=progress

Example:

dd status=progress if=/dev/sda of=/dev/sdb

Notice how I didn’t add the bs option and used the default. In my experiences the default works best.

Tested on: Ubuntu

Top 15 Countries by Coders

I have analyzed the data from HackerRank (December 7 2016) to find out the Top 15 countries in the world by cumulative ranking as well as by the number of Institutions in Top 50.

In order to figure out which colleges have the best coders, HackerRank hosted a major University Rankings Competition. Over 5,500 students from 126 schools from around the world participated in the event.

Cumulative Coder Rank of Top 15 Countries

India is the clear leader with cumulative score of 2901.04, more than double of US with cumulative rank of 1113.22. Russia is a distant third with less than 1/2 of US rank. But how does it fare in the total number of Institutions in the Top 50?

Country Sum – Rank
India 2901.74
US 1113.22
Russia 668.07
Romania 412.35
Canada 398.8
China 387.18
Vietnam 321.99
Ukraine 255.83
Sweden 231.23
Czech Republic 188.67
Turkey 157.56
Kazakhstan 138.87
Poland 130.34
Belgium 125.91
South Korea 124.65

Note: The score / rank of a College is weighted average and hence can be summed to get cumulative scores.

Top 15 Countries by Total Count of Institutions in Top 50

22 Institutions in India rank in the Top 50. US, second placed, is by contrast can boast of only 8 Institutions, almost 1/3 of India.

Country Count – Rank
India 22
US 8
Romania 3
Canada 2
Russia 2
Belgium 1
Bosnia & Herzegovina 1
China 1
Czech Republic 1
Estonia 1
Kazakhstan 1
Mexico 1
Poland 1
South Korea 1
Sweden 1

No wonder India is the top destination for outsourcing across the world. It produces very large number of Top Coders according to HackerRank data.

Within India the top 2 Institutions are IIT, Indore followed by IIT, Kanpur.

Java: The Most Popular Programming Language Today

Several research independently confirms Java as the most popular programing language today and as such can be considered the safest bet for someone looking to make a career in programming or looking for a career change. Let’s look in details below.

The TIOBE Index

The TIOBE Index for February 2017 indicates Java is the most popular programming language today. Java’s popularity is almost double that of the next contender C.

The TIOBE Programming Community index is an indicator of the popularity of programming languages. The index is updated once a month. The ratings are based on the number of skilled engineers world-wide, courses and third party vendors. Popular search engines such as Google, Bing, Yahoo!, Wikipedia, Amazon, YouTube and Baidu are used to calculate the ratings. It is important to note that the TIOBE index is not about the best programming language or the language in which most lines of code have been written.

PYPL PopularitY of Programming Language

The PYPL PopularitY of Programming Language Index is created by analyzing how often language tutorials are searched on Google.

The more a language tutorial is searched, the more popular the language is assumed to be. It is a leading indicator. The raw data comes from Google Trends.

If you believe in collective wisdom, the PYPL Popularity of Programming Language index can help you decide which language to study, or which one to use in a new software project.

PYPL too indicates Java as the leading programming language.

CodingDojo

CodingDojo diligently compiled job data from indeed in 2016 which shows Java is the top in-demand programming language, unless you consider SQL as programming language.http://www.inc.com/larry-kim/10-most-popular-programming-languages-today.html

Inc.com

Inc.com does not cite sources but states Java as the most popular programming language. Larry Kim, Founder and CTO of WordStreaam, gives a nice summary:

Java is top pick as one of the most popular programming languages, used for building server-side applications to video games and mobile apps. It’s also the core foundation for developing Android apps, making it a favorite of many programmers. With its WORA mantra (write once, run anywhere), it’s designed to be portable and run happily across multiple software platforms.

So if you are searching for a programming language to learn to build your career then look no further and start coding in Java.

Footnote: Glassdoor data indicates Software Architect is the highest paying job in this field, followed closely by Software Development Manager.

Key differences between Understanding and Learning (Memorization)

Many Educational Institutes, even today, do not focus on understanding. Their tests can be easily passed with memorization. This weakens the foundation of the students and adversely affects his future performance in professional engagements. Let’s look at the key differences between understanding and memorization and why understanding should be the priority for all students.

Memorization is simple. We all know that by repeated reading of any subject matter we can remember it by heart and be able to regurgitate (repeat information without analyzing or comprehending it) on demand, even matching similar sounding questions with the answer you have learned. And that is pretty much all you need to get through in most school systems and even most colleges.

Understanding, on the other hand, is knowing the underlying ideas and concepts so well that you can then explain them in your own words, even if you do not remember any of the terminology used. It allows you to develop insights that comes from inductive or deductive reasoning on the concepts.

You know you have understood something well when you can apply it to real life situations and clearly explain it to a layman with ease.

With understanding your can identify the similarities and differences between similar sounding ideas on your own.

Understanding is the key to advancing knowledge and discovering new knowledge.

Understanding is what is useful in real life, learning alone takes us nowhere.

Today computers can store much more facts than you will ever learn and can regurgitate it faster, even for complex queries (like Google). Instead of focusing your energies on memorization, which is anyways a losing and pointless battle, why not focus on understanding the topic at hand?

You will find that when you understand any topic, you tend to remember the key words and phrases too, thereby serving both the purposes of your exams as well as much bigger purpose of excelling real life and profession.

How to Easily Configure WiFi in Raspberry Pi

Any version of Raspberry Pi can be very easily configured with WiFi access. Coupled with ssh or vnc, it allows you to manage your Pi remotely. Here is the simplest way I could think of, illustrated by a screenshot and detailed below.

Once your Raspberry Pi boots up, you will get to this shiny screen. Now open a Terminal by clicking on the black square icon on top-left of the screen.Screenshot from 2017-01-04 11-29-18

This opens a Terminal where you type in:

sudo leafpad /etc/network/interfaces

This opens up a notepad-like editor. Make three changes to the text as shown in the highlighted section:

  1. Change manual to dhcp in the line starting with “iface wlan0”
  2. Replace wifi_id with the Wireless Access ID / SSID
  3. Replace password with your actual password for Wireless Access

Now save it (Ctrl-S) like notepad and exit it. The terminal should still remain open.

Now either reboot the Pi or restart the network with the following command on Terminal (don’t forget to press <Enter> after you typed):

sudo service networking restart

Wait for a few minutes for the WiFi to come up. On latest Raspbian with PIXEL, you can verify by seeing the two blue arrows in opposite direction, as can be seen from the screenshot.

Steps to secure and protect your Skype account from Hacking

Skype accounts are being hacked since at least August last year. Breached Skype accounts are used to send thousands of spam messages before they’re locked by Microsoft. The owners then have to regain access and that is when most find out about it. Skype has fallen victim to similar attacks before, and hackers were able to spoof messages on the system in 2015 after using lists of stolen usernames and passwords to gain access to accounts.

Problem

This wave of attack appears to be growing in size, and Skype users who opted for Microsoft’s two-factor security are also vulnerable. Microsoft offers the ability to link a Skype and Microsoft Account together to make sign-in and security easier. It turns out that Microsoft keeps your original Skype account password separate so that it can still be used to access the service with a Skype username. If that password isn’t secure then hackers can use it to gain access to your Skype account, bypassing any two-factor authentication provided by Microsoft. Essentially Microsoft has left a backdoor open to their vaunted two-factor security! It can be safely assumed that the new wave of attack is dictionary based and Skype / Microsoft allows unlimited login tries at some entry point.

Solution

The solution, in brief, is to switch to Microsoft’s two-factor security and then disable access by old method.

1. Update your Skype account to a Microsoft account:

  • Go to https://account.microsoft.com, if you’re already signed in, sign out.
  • Enter your Skype name and password when prompted and then select
  • Sign in.
  • If your Skype account is not updated already, you will be notified to update your account.
  • Select Next to continue.
  • You will be asked to add an email to your account, and verify that email.
  • Congrats, your Skype account is also a Microsoft account.

2. Ensure that your Accounts are fully merged:

  • Go to https://account.microsoft.com, if you’re already signed in, sign out.
  • Enter your Skype name, not your Microsoft Account email address, and use your Skype password to sign-in
  • If you’ve linked your Microsoft Account previously, you’ll be prompted to sign-in and merge the accounts to create a Skype alias

3. Disable Skype alias:

Once the two accounts are properly merged, Microsoft creates a Skype alias to let you keep signing in with a Skype username. Disable it under the aliases preferences, to ensure complete protection.

Maximum number of Files in a Directory

Different file systems in different Operating Systems has different limitations in the number of files that can be in a directory as determined by the underlying architecture.. Here is an overview of maximum of number of files that you can have in a directory and associated problems, if any, like performance.

FAT32

  • Maximum number of files: 268,173,300
  • Maximum number of files per directory: 216 – 1 (65,535)
  • Maximum file size: 2 GiB – 1 without LFS, 4 GiB – 1 with

NTFS

  • Maximum number of files: 232 – 1 (4,294,967,295)
  • Maximum file size
    • Implementation: 244 – 26 bytes (16 TiB – 64 KiB)
    • Theoretical: 264 – 26 bytes (16 EiB – 64 KiB)
  • Maximum volume size
    • Implementation: 232 – 1 clusters (256 TiB – 64 KiB)
    • Theoretical: 264 – 1 clusters

ext2

  • Maximum number of files: 1018
  • Maximum number of files per directory: ~1.3 × 1020 (performance issues past 10,000)
  • Maximum file size
    • 16 GiB (block size of 1 KiB)
    • 256 GiB (block size of 2 KiB)
    • 2 TiB (block size of 4 KiB)
    • 2 TiB (block size of 8 KiB)
  • Maximum volume size
    • 4 TiB (block size of 1 KiB)
    • 8 TiB (block size of 2 KiB)
    • 16 TiB (block size of 4 KiB)
    • 32 TiB (block size of 8 KiB)

ext3

  • Maximum number of files: minimum (volume Size / 213, number of Blocks)
  • Maximum file size: same as ext2
  • Maximum volume size: same as ext2

ext4

  • Maximum number of files: 232 – 1 (4,294,967,295)
  • Maximum number of files per directory: unlimited
  • Maximum file size: 244 – 1 bytes (16 TiB – 1)
  • Maximum volume size: 248 – 1 bytes (256 TiB – 1)

Possible causes & solutions for MongoDB not running

Is your MongoDB properly running? A simple way to check it would be with:

service mongod status

On my CentOS 5.x it gave:

mongod dead but subsys locked

There are two possible causes I could find. First is related to disk space. If you do not have enough space for dbpath (database directory) then you may get this message.

To solve it you can add following to the config file provided when running mongod --config mongod.conf

For MongoDB 3.x (latest version)

storage:
   mmapv1:
      smallFiles: true

For version 2.6+

storage:
   smallFiles: true

For version 2.4 and less

smallfiles = true

Then just execute mongod to accept your config file (here it assumes that location of the config is /etc/mongodb.conf):

mongod -f /etc/mongodb.conf

Documentation for smallfiles parameter:

Set to true to modify MongoDB to use a smaller default data file size. 
Specifically, smallfiles reduces the initial size for data files and
limits them to 512 megabytes. The smallfiles setting also reduces the
size of each journal files from 1 gigabyte to 128 megabytes.
Alternatively you can run mongod with --smallfiles parameter like:
mongod --smallfiles

On my machine the problem was different. It was expecting a directory /var/lib/mongod with proper permissions, which was not there. The solution is simple:

sudo mkdir /var/lib/mongod
sudo chown -R mongod /var/lib/mongod

However how did I find out about the problem(s) in the first place. Again the solution is very simple. I looked in the log file:

vi /var/log/mongodb/mongodb.log

Always start with the log file.

Finally you can verify that your system is running properly with:

sudo service mongod status

After fixing it gave:

mongod (pid 26194) is running...

Now that’s solved, let’s get back to mongodb coding..

Ubuntu: How to Change Host name and Propagate to DHCP Server

How to change Hostname on Ubuntu

First find your current host name by typing:

hostname

Open /etc/hostname and change the host name specified there to the new host name.

sudo vi /etc/hostname

Now open /etc/hosts and locate the old host name in the file and change it to the new host name.

sudo vi /etc/hosts

Now restart hostname with:

sudo service hostname restart

How to propagate Hostname Change to DHCP Server and other machines

The chosen host name should be propagated to the DHCP server so that any other computer can refer to this computer by your new chosen hostname. To do that run the following commands:

sudo dhcclient -r ; sudo dhclient

Now you should be able to access this machine by its newly chosen host name from any other machine in the same network and served the same DHCP server.

An exception would be if a machine is configured statically or not configured to use the name server associated with this dhcp server.

Most routers today comes with DHCP server and an associated Name Server which can be configured as shown above.

Suggestions for Raspberry Pi Demo & Tutorial for Engineering Students

Next week I am giving a demo of Raspberry Pi and a Tutorial to Engineering students, primarily from Electronics & Computer Science department. I am collecting suggestions on what to show them in this seminar. Currently I have thought about the following items

  • How to use Raspberry Pi to create a mini FM Radio Station as a cool example to get them hooked on Pi
  • How to write simple Java Programs with built-in IDE to show the capability of Pi

What else do you think I should show and tell?