Camera Module Raspberry PI

One of the top uses of Rapi is to use it as a motion detector device by using camera module. It is not that complicated, it is really easy though.

I simplify the process into steps to make it easier to understand.

1) Update and upgrade package management system.

sudo apt-get update
sudo apt-get upgrade

2) Activate and enable camera module
 sudo raspi-config

It shows selection window, and we select Interfaces and then camera. After confirmation, it installs camera module. Now, we can capture still image or video if camera is properly installed.


3) Installation of camera



The camera is connected as shown above. The camera interface is located beside the network port. Note that the shiny part of the ribbon should always point outward from the network port. (See the pic above).

raspistill -o image.jpg
raspivid -o video.h264 -t 10000 

The time is in milliseconds. First command capture an image while second captures a 10 seconds video. 

4) Streaming and Motion Detection

Now, we go further and implement our Raspberry Pi device as a motion detector device. A very nice package is there called motion  which is highly recommended.

sudo apt-get install motion
sudo systemctl status motion.service
sudo systemctl start motion.service 


After completion, we have to modify some settings according to our requirements. We also need to enable video module for video device to work.

sudo modprobe bcm2835-v4l2

Everytime, to automaticlly enable video module, we put this command in /etc/rc.local(sudo is not needed there)

Again we need to enable motion daemon in
/etc/default/motion file.

start_motion_daemon=yes

Now, we carry out settings in /etc/motion/motion.conf. The file is really big, but we have to focus on a few things:

width 1200
height 800
framerate 20
target_dir /var/lib/motion
picture_filename %Y_%m_%d/%v-%Y%m%d%H%M%S-%q
movie_filename %Y_%m_%d/%v-%Y%m%d%H%M%S
stream_port 8081
stream_localhost off # stream connections to other systems
webcontrol_localhost off

The above mentioned parameters quite easy to understand. After change, we need to restart motion.


Now, we see the motion detected pictures stored in the directory /var/lib/motion and the define directory and file structure. And also we can access the live stream from the link:
http://IP_ADDRESS_OF_PI:8081

Thats it!

It is interesting, is not it?

Raspberry Pi Settings

Hello guys, today, I am gonna share with you guys something different from programming, however, would be an interesting. Yes, Raspberry Pi is a computer, somebody would rather say "mini-computer". This is tiny but really powerful machine, on the other hand, consumes less power and resources. So, the best application of this device is to run 24/7 as embedded. I have looked around the online markets and the latest version is pi 3 (2015) costs around 38.00 €. This is powerful enough to carry out general tasks. It is suggested to buy memory card and housing also for better installment and other accessories based on requirements.

1) Operating System Installation

I have installed Raspbian Jessie Lite which is mini operating system and needs less space to install. I prefer mini version because we can later install whatever we want, rather than having unwanted application installed. The downloads are located here

https://www.raspberrypi.org/downloads/raspbian/

 The extraction of zip file gives an image which we have to write into our memory card. (Raspberry pi 3 needs micro SD card).

Raspberry Pi recommends Etcher tool to write images into the SD card, it is really cool tool for writing to SSD cards and it is available for Linux system also.

https://etcher.io/

After installation, we can run Etcher, then select image and drive and flash button. Just three step, and wait for a couple of minutes until flashing finishes,

2) Configuration

After image writing completes, we are ready to run Raspbian in our Raspberry Pi. Please note that the installed operating system has not GUI and we need to remotely access it and use secure connection tool (SSH) to connect it. To carry out this,we have two challenges, first, by default, the new operating systems have disabled SSH, second, for wifi connection, we need to set the wifi credentials also. So, lets begin:

a) Set WIFI

Via NIC card, the connection is automatic, we need to do nothing. The are nice tools (I used from http://angryip.org/) available and we can find out the IP address of the device. The default host-name is raspberry.

For WLAN, we have to provide WIFI information. We create a file wpa_supplicant.conf with the following information:

network={
    ssid="YOUR_SSID"
    psk="YOUR_PASSWORD"
    key_mgmt=WPA-PSK
}

b) Enable SSH

There is a boot folder in the written image and we just create a file "ssh" (WITHOUT extension) in this folder, at the time of booting, it enables SSH so that use pi can access this with Secure Shell.

Default user name: pi
Default password: raspberry

For security reasons, it is advisable to change the password after you logged in.


Some Questions:

1) What is the power supply for Raspberry PI?
Raspberry Pi is really really cool, because it is suitable for everywhere regarding power supply. The smartphone charging cable completely fits. We can use our computer USB port or separate device(that comes with mobile charger) to provide power . That is enough!

2) Is there any chances of overheating CPU?
The short answer is no, because Raspberry PI manages itself to save from overheating and burning. It automatically detect the overheating and accordingly manages the frequency of CPU to reduce the temperature. So, basically saying, the temperature of RaPi never reach above 65 degree and you need not worry about temperate of Rapi which is above normal. The normal temperature is assumed to be 40-45 degrees. My RaPi always around 50 degree with normal operation and it reaches to 60 degree when I implement camera streaming application(motion). However, somebody prefers some cooling mechanism( head sink or fans). Heat Sink is okay, not recommended though, but use of fan makes simple Raspberry complicated, even a bit noisy.


Disclaimer: I have tested with Raspberry PI 3 version 1.3 (2015), may be the process is not exact for other Pi devices. 

Unit Testing in Java

Why Testing? 

Testing is necessary to deliver a good quality product. Nobody is perfect and the development phase of a software is prone to error. So, if we find the software bugs at the beginning phase, we can reduce the maintenance cost. So, we need proper testing while we do programming and the developer can himself carry out some tests whether his function is working as desired. Basically, it is tedious to manually test all possibilities and the developer himself has tendency to test best case scenarios. But the output product is used by users who never know the details about it. So, a third party user has higher possibilities to discover bugs. But we do not get this chance until we deliver the product, and the customer also do not like buggy software, so the final delivered product should be Bug-Free.

JUnit Testing

In this article, I am sharing the steps on how we can use JUnit framework to test java classes.  To use JUnit testing, we need to include library file in class path. It can be downloaded from www.junit.org and include it as reference library.

How?

1) The unit testing files should be normally separated, you know why? These files are testing files only needed to developer, not the user. So, it is good practice not to include these test files in the production mode. Thus we create a separate folder to store test files.

2) Packaging makes it everything clear. So, we create the same package, and test classes with suffix Test.

Suppose, we create a class

package com.krishna.math;

public class MathFunction{
       private  int A;
       private int B;
       public MathFunction(int A, int B){
         this.A=A;
         this.B=B;
     }
    
public int getSum(){
     return this.A+this.B;
}

public int getDiff(){
    return this.A-this.B;
}  

} 


Now, we create a test class. The above mentioned class MathFunction resides in src folder, while we create another folder test to store test files. Gradle and maven projects default structure is:

source: /src/main/java
test: /src/test/java

So, under test folder, we define a class to test the above-mentioned class functions:

package com.krishna.math;

import static org.junit.Assert.*;

import org.junit.Test;

public class MathFunctionTest{
     //Write test methods here
     @Test 
     public void testSum(){
       MathFunction mathFunction=new MathFunction(12,34);
       assertEquals(46, mathFunction.getSum());
     }

   @Test
   public void testDIff(){
    MathFunction mathFunction=new MathFunction(13,12);
    assertEquals(1, mathFunction.getDiff());
    }
}


So far so good, we can run it directly from eclipse, just right click and run as JUnit. That shows the test result. 

Running Multiple Tests (TestSuite Class )

The above mentioned method runs one test case (test class) at at time. But we are interested to test all test cases as a whole. So, the need of test suite class arises.

We define a test suite class as follows:

import org.junit.runner.RunWith
import org.junit.runners.Suite;

import org.junit.runners.Suite.SuiteClasses;

@RunWith(Suite.class)
@SuiteClasses({ LinkedListTest.class, MyStackTest.class })
public class AllTests {

}

After, we run it from eclipse IDE, it works like a charm. You see the result with proper coloring also, Eclipse helps you!

Test Automation 
So far, we have created test cases and test suite which is run by eclipse. What if you wanna run and get result and do some process. For that you need a test runner. It is an independent runner and you have control over the result of the test. You may create a separate class for test runner or just add it in TestSuite class. 


I create a separate class as follows:

import org.junit.runner.JUnitCore;

import org.junit.runner.Result;

import org.junit.runner.notification.Failure;

public class TestRunner{
public static void main(String[] args) {
Result result = JUnitCore.runClasses(AllTests.class);
for (Failure failure : result.getFailures()) {
System.out.println(failure.toString());
}

System.out.println(result.wasSuccessful());

}
}


The examples presented are just sample, the real test cases tend to have many methods. 

MySQL Server Installation

1. INTRODUCTION

Installation of mySQL Server in linux system is not that difficult. We just need to run a couple of commands and thats it!

2. INSTALLATION
 
Here are the required commands to install and prepare mysql server:

sudo apt-get update
sudo apt-get install mysql-server
sudo mysql_secure_installation 

Check the status of mysql server

sudo systemstl status mysql.service

This above command should show Active: active (running)  as output which means it is running.

The administration of mysql is carried out with mysqladmin command which can be run from terminal as follows:

mysqladmin -p -u root version

This will show the version information along with other information. 

3. LOCAL CONNECTION

We can use mysql to connect to the server as follows:

mysql -u root -p -h localhost

After connection, we need some basic commands as follows:

show databases;
use db_name;  
show tables; 
select * from [TABLE_NAME];
exit

We can see all the command by typing \h. 

 4. REMOTE CONNECTION

Local connection is not the problem we can directly use local server. But for security reasons, we can not connect if server is located remotely. We have to define some configuration settings to carry out remote connection. 

cd /etc/mysql/mysql.conf.d
sudo vi /mysql.conf.d

Check the section [mysqld] and modify the bind-address with the ip address of the server as follows:
bind-address =10.8.102.62

After restarting the server, we can now connect remotely.

Note: mysql uses port 3306, so this port should not be blocked from firewall. 

5. REMOTE USER CONFIGURATION 

Yes, the default root user is so configured that, only can connect locally. So, next task is to define this user so that it can connect remotely. That we do after carrying out local connection.

mysql -u root -p localhost
 
SELECT host FROM mysql.user WHERE User='root';

It shows localhost or 127.0.0.1 which means this user can not connect remotely. 

CREATE USER 'root'@'%' IDENTIFIED BY '[PASSORD]’;
GRANT ALL PRIVILEGES ON *.* TO 'root'@'%';

Reload permissions:

FLUSH PRIVIOLEGES;


Now, we can connect remotely with root user. % signifies the acceptance of connection from any external sources. 

Cassandra Walkthrough

INTRODUCTION

Today I am gonna write something about Cassandra database system.  Yes, first question comes in mind is why on earth do we need this database while already there are other more popular databases. Yes, that is true as far as our relational database has less amount of data. Since Company grows, so the database, and the conventional relational databases do not sufficiently fulfill our requirements to hold such a big data. We have to think about some alternative databases which overcomes this problem i.e. these no-SQL databases can store and access efficiently huge data.

WHY CASSANDRA?

Cassandra is no-SQL database which is used by large companies to store big data. The storage structure of cassandra is different from that of relational databases and provides faster data access with support of data replication in clusters. So, basically, cassandra can store huge data and faster access of data.

INSTALLATION

The installation of cassandra is very simple. We need to download cassandra from here

http://cassandra.apache.org/

in *.tar.gz format. We have to extract it somewhere (e.g. /opt/cassandra) and this is the root directory of cassandra.

So, to directly access cassandra related commands, we have to define /opt/cassandra/bin ad PATH directory. Just add this to /etc/environment file and restart the system.


STARTING THE SERVER

The cassandra/bin directory contains all the executables needed. To start server

cassandra -f (starts server in background, that makes it easier to close the server, just with CTRL+C)
cassandra This will start server in background. To close server, we have to kill the cassandra process id.

pgrep -f CassandraDaemon  (gets pid of cassandra)
kill pid or pkill -f CassandraDaemon

After server is started we can use the cassandra client to connect. Cassandra comes with a very handy client tool called cqlsh which connects to the cassandra server and we can execute queries to carry out database operations.

nodetool status
(Checks if cassandra is running )

Connection and running commands:
cqlsh localhost
cqlsh localhost -u cassandra -p cassandra 
describe keyspaces
use [KEYSPACE]
describe tables
exit  



NETWORK CONNECTION

Cassandra, by default, can be connected locally. That means, we have to do some changes in conf/cassandra.yaml file to carry out connection from network.
We have to not that, to carry out connection from network, the  port 9042 should not be blocked by firewall applications.

To carry out the changes, we open the file:

conf/cassandra.yaml

and fine the line listen_address line, and comment out, and define the IP address of the server.  e.g.

listen_address: 10.8.102.62

Again, we change the rpc_address also,

rpc_address: 0.0.0.0

and finally, we change the broadcast address 

broadcast_rpc_address: 10.8.102.255

If rpc_address is defined as a fixed address, then we can leave broadcast_rpc_address blank or commented. 

And, finally, we add seed provider also, here we have to add the ip-address as a seed provider. 

Just find the line which seed_provider and go to parameters, and there is already one seed defined, and you have to add the ip-address of the cassandra server. 

- seeds: "127. 0.0.1,10.8.102.62"

We save this configuration and restart server. Now, we can connect to the server from another computer in the network:


cqlsh 10.8.102.62


 

Deploying Django Project

Last couple of days, I am concentrating on python and giving some time in python related research. Initially, I found it really good for scripting, and later I noticed that it is really powerful language, can be used for desktop to web applications, from small testing applications to a big project.

Django is a framework developed in python and the web development using this framework makes the task simple, clear separation between view and controller. The view templates even can not insert custom codes, that is great, which separates coding from view(coding makes mess in html code)

So, creating a sample Django application and running through command is very easy which can be used for development purpose. And good thing is that, the changed code is reflected when browser is reloaded, that means we do not need to recompile the code. But what if I want to deploy to a dedicated server (I mean Apache2) ? It is not straight forward. Although there are many different possible configurations, I will focus on the basic configuration that make the website running.  Later we can extend it with more and more.


So, let us begin it.

1) Virtualenv

There might be other methods also, I will explain the methods which needs creation of virtualenv. So, first of all, we need python-pip which can be installed with

sudo apt-get install pip
sudo pip install virtualenv


I normally used Eclipse IDE and for a django project I have instally PyDev plugin which makes the task easier. With eclipse I create a Django project and after you have created it , you can directly test it(Thanks Eclipse, it creates everything for you).

Now we install virtualenv inside the directory so that we can deploy the whole directory to new server without worrying the server.

So, we run the following command from inside the project folder:

virtualenv ENV

Then,

activate it

source ENV/bin/activate


2) Install Django

We can now install django module using

pip install django

So, the basic project is ready to deploy.


3) Server Preparation

a) Module wsgi

My assumption is that we already installed apache2 . That is not enough, we need to install libapache2-mod-wsgi module also.

sudo apt-get install libapache2-mod-wsgi-py3
* py3 here means python 3
Now we provide the access definition for wsgi.py file in the project.

b) apache2.conf
We write the following line in /etc/apache2/apache2.conf

<Directory /Backup/workspace/java/misc/DjangoProject>
        <Files wsgi.py>
                Require all granted
        </Files>

c) Define site

Now, finally,  we define and enable site in /etc/apache2/sites-available. We create a file 0001-python.conf (for e.g.) with the following contents:

WSGIDaemonProcess sampleapp python-path=/Backup/workspace/java/misc/DjangoProject:/Backup/workspace/java/misc/DjangoProject/ENV/lib/python3.4/site-packages
WSGIProcessGroup sampleapp
WSGIScriptAlias /sampleapp /Backup/workspace/java/misc/DjangoProject/DjangoProject/wsgi.py

And enable this site :

sudo a2ensite 0001-python.conf

sudo apt-get apache2 restart

Now, check your Django application running with the following URL:

http://localhost/sampleapp

Enjoy , you have successfully deploy your first Django application.


References:

https://docs.djangoproject.com/en/1.9/howto/deployment/wsgi/modwsgi/
https://www.digitalocean.com/community/tutorials/how-to-run-django-with-mod_wsgi-and-apache-with-a-virtualenv-python-environment-on-a-debian-vps

Apache2 Server Subdomains

Apache2 Server configuration for multiple web applications is confusing for beginners. Since I have just started configuring apache server in my Ubuntu 14.04 system, I am going to share my experiences while installing and configuring Apache Server.

Basic Commands

Here are the basic commands need to learn:

1) Installation :
       sudo apt-get install apache2
2) Reload:
       sudo service apache2 reload
3) Restart:
       sudo service apache2 restart
4) Enable website:
       sudo a2ensite [WEBSITE_NAME]
5) Disable website:
       sudo a2dissite [WEBSITE_NAME]

Problem Scenario

So, the problem scenario is I have to install multiple web applications in the same host but with different URLs. And the web applications can be placed anywhere in the server. And I also discuss about defining sub-domains. 

For example, I have three web projects located in /home/frietec/www/redmine, /home/frietec/www/owncloud, /home/frietec/www/ldap and I want to access these projects with redmine.frietec.com, cloud.frietec.com, ldap.frietec.com.

Solution

The solution for this is not so difficult. We need to configure virtual host.  First of all, we have to define the virtual hosts in config file as below:

    DocumentRoot /home/kris/public_html
    ServerName myproject.localhost

    # Other directives here




    DocumentRoot /home/kris/public_html/myproject
    ServerName myotherproject.localhost
  
    # Other directives here

In this example, it is important that the defined sub-domains should point to the same local machine. So, we either place this information to a DNS server to publicly access. To test in local network, we modify the file /etc/hosts with the subdomains point to the same IP. This way removed the burgeon of remembering the ip-address of the system.

File: /etc/hosts

 127.0.0.1      localhost
 127.0.1.1      kpsharma
 192.168.1.82   myproject.localhost
 192.168.1.82   myotherproject.localhost 



Note: if we use IP address instead of domain-name, then it uses the topmost virtual host. In this case, the project "myproject.localhost" is called.