Applied Code

Ajenti: Web based Control panel for managing linux server

2015-08-10T10:37:00.001-07:00

Ajenti is an open-source web based system Management control panel for managing remote system administrating tasks from the browser similiar to Webmin module. It is a much powerful and lightweighted tool, that provides fast and responsive web interface for managing small server setups and best suitable for VPS and dedicated servers.

It can install packages and run commands, and you can view basic server information such as RAM in use, free disk space, etc. All this can be accessed from a web browser.
Optionally, an add-on package called Ajenti V allows you to manage multiple websites from the same control panel.

Pre-requisites for Ajenti:

1. Registered Domain name
2. Setup hostname on the Server on which you are going to setup the Ajenti CP.
3. A non-root user with sudo privileges.

Installing Ajenti

On your server, as a user with sudo access, first add the repository key. This is used to validate the sources of the Ajenti packages you will be installing.

 $ wget http://repo.ajenti.org/debian/key -O- | sudo apt-key add -

Then add the actual repository to your sources list:

 $ echo "deb http://repo.ajenti.org/ng/debian main main ubuntu" | sudo tee -a /etc/apt/sources.list

Now you can update your packages and begin the install process by running:

 $ sudo apt-get update && sudo apt-get install ajenti

When it prompts you to continue, type Y and press ENTER. The install process may take a few minutes. After the process is over, start the Ajenti server:

 $ sudo service ajenti restart

Configuring Ajenti

Now, you ajenti is installed, need to configure and it will by default take all the default metrics of server. Open a web browser and browse to https://panel.your_domain_name:8000/ or https://IP:8000/.

Log in with these default credentials:

Username: root

Password: admin

You will now be inside your new Ajenti control panel.

Plugins

Ajenti already has a lot of functionality built in by default, but if you want even more settings and configurable items in your panel, you can check out the Plugins section. Some plugins are enabled by default, while others aren't, usually due to unsatisfied dependancies.

You can install disabled plugins by clicking on them in the Plugins menu and pressing the button next to the dependency it requires. Otherwise, if you later install an application manually and Ajenti has a plugin for, you can restart Ajenti and the corresponding menu should appear next time you log in.

System Management

Under the System section in the sidebar, there's a plethora of configurable items to choose from. You can manage hard drives with the Filesystems menu.

Congratulations: Ajenti control panel is installed on the server. Now, use it to manage server.

Mail Server: OFBiz with Mysql Setup

2015-08-08T07:45:00.000-07:00

Apache OFBiz™ is an open source product for the automation of enterprise processes that includes framework components and business applications for ERP (Enterprise Resource Planning), CRM (Customer Relationship Management), E-Business / E-Commerce, SCM (Supply Chain Management), MRP (Manufacturing Resource Planning), MMS/EAM (Maintenance Management System/Enterprise Asset Management), POS (Point Of Sale).

Apache OFBiz is licensed under the Apache License Version 2.0 and is part of The Apache Software Foundation.

Step 1: Install JAVA

Java is the primary requirement for installing Apache OFBiz. It required minimum Java 1.6 to installed on your system. Make sure you have Java installed with proper version on your system.

 # java -version

If you do not Java installed, Use below tutorial to install java else ignore it.

For Ubuntu, Debian and LinuxMint Users – Install JAVA 7 or Install JAVA 8

Step 2: Install Mysql and Setup for OFBiz

MySQL is a powerful database management system used for organizing and retrieving data

To install MySQL, open terminal and type in these commands:

 sudo apt-get install mysql-server libapache2-mod-auth-mysql php5-mysql

During the installation, MySQL will ask you to set a root password. If you miss the chance to set the password while the program is installing, it is very easy to set the password later from within the MySQL shell.

Once you have installed MySQL, we should activate it with this command:

 sudo mysql_install_db

Creating Databases and user access for OFBiz

We will be creating databases and user access which will be used with ofbiz to store the data. Below are the commands:

 mysql>create database ofbiz;  
 mysql>create database ofbizolap;  
 mysql>create database ofbiztenant;  
 mysql>use mysql;  
 mysql>select database();  
 mysql>create user ofbiz@localhost;  
 mysql>create user ofbizolap@localhost;  
 mysql>create user ofbiztenant@localhost;  
 mysql>update user set password=PASSWORD("ofbiz") where User='ofbiz';  
 mysql>update user set password=PASSWORD("ofbizolap") where User='ofbizolap';  
 mysql>update user set password=PASSWORD("ofbiztenant") where User='ofbiztenant';  
 mysql>grant all privileges on *.* to 'ofbiz'@localhost identified by 'ofbiz';  
 mysql>grant all privileges on *.* to 'ofbizolap'@localhost identified by 'ofbizolap';  
 mysql>grant all privileges on *.* to 'ofbiztenant'@localhost identified by 'ofbiztenant';

Step 3: Download Apache OFBiz from SVN

We will be using SVN download latest Apache OFBiz files. first make sure you have svn client installed on system after that checkout the latest build from the subversion repository of OFBiz.

 # cd /opt/  
 # yum install subversion  
 # svn co http://svn.apache.org/repos/asf/ofbiz/trunk apache-ofbiz

Step 4: Integrating Apache OFBiz with Mysql

Before we build Apache OFBiz, we will be integrating it with Mysql
1. Firstly, will be needing the JDBC connector: mysql-connector-java-5.1.14-bin.jar - to be placed in <ofbiz-dir>/framework/entity/lib/jdbc
2. Create a backup of apache-ofbiz/framework/entity/config/entityengine.xml
3. Edit entityengine.xml as follows:
a. Add the following datasources below the datasource 'localmysql'

 <datasource name="localmysqlolap"  
     helper-class="org.ofbiz.entity.datasource.GenericHelperDAO"  
     field-type-name="mysql"  
     check-on-start="true"  
     add-missing-on-start="true"  
     check-pks-on-start="false"  
     use-foreign-keys="true"  
     join-style="ansi-no-parenthesis"  
     alias-view-columns="false"  
     drop-fk-use-foreign-key-keyword="true"  
     table-type="InnoDB"  
     character-set="latin1"  
     collate="latin1_general_cs">  
   <read-data reader-name="seed"/>  
   <read-data reader-name="seed-initial"/>  
   <read-data reader-name="demo"/>  
   <read-data reader-name="ext"/>  
   <inline-jdbc  
       jdbc-driver="com.mysql.jdbc.Driver"  
       jdbc-uri="jdbc:mysql://127.0.0.1/ofbiz?autoReconnect=true"  
       jdbc-username="ofbizolap"  
       jdbc-password="ofbizolap"  
       isolation-level="ReadCommitted"  
       pool-minsize="2"  
       pool-maxsize="250"  
       time-between-eviction-runs-millis="600000"/>  
 </datasource>  
 <datasource name="localmysqltenant"  
     helper-class="org.ofbiz.entity.datasource.GenericHelperDAO"  
     field-type-name="mysql"  
     check-on-start="true"  
     add-missing-on-start="true"  
     check-pks-on-start="false"  
     use-foreign-keys="true"  
     join-style="ansi-no-parenthesis"  
     alias-view-columns="false"  
     drop-fk-use-foreign-key-keyword="true"  
     table-type="InnoDB"  
     character-set="latin1"  
     collate="latin1_general_cs">  
   <read-data reader-name="seed"/>  
   <read-data reader-name="seed-initial"/>  
   <read-data reader-name="demo"/>  
   <read-data reader-name="ext"/>  
   <inline-jdbc  
       jdbc-driver="com.mysql.jdbc.Driver"  
       jdbc-uri="jdbc:mysql://127.0.0.1/ofbiz?autoReconnect=true"  
       jdbc-username="ofbiztenant"  
       jdbc-password="ofbiztenant"  
       isolation-level="ReadCommitted"  
       pool-minsize="2"  
       pool-maxsize="250"  
       time-between-eviction-runs-millis="600000"/>  
 </datasource>

b. Replace derby with mysql in default, default-no-eca and test delegators as follows:

 <delegator name="default" entity-model-reader="main" entity-group-reader="main" entity-eca-reader="main" distributed-cache-clear-enabled="false">  
   <group-map group-name="org.ofbiz" datasource-name="localmysql"/>  
   <group-map group-name="org.ofbiz.olap" datasource-name="localmysqlolap"/>  
   <group-map group-name="org.ofbiz.tenant" datasource-name="localmysqltenant"/>  
 </delegator>  
 <delegator name="default-no-eca" entity-model-reader="main" entity-group-reader="main" entity-eca-reader="main" entity-eca-enabled="false" distributed-cache-clear-enabled="false">  
   <group-map group-name="org.ofbiz" datasource-name="localmysql"/>  
   <group-map group-name="org.ofbiz.olap" datasource-name="localmysqlolap"/>  
   <group-map group-name="org.ofbiz.tenant" datasource-name="localmysqltenant"/>  
 </delegator>  
 <delegator name="test" entity-model-reader="main" entity-group-reader="main" entity-eca-reader="main">  
   <group-map group-name="org.ofbiz" datasource-name="localmysql"/>  
   <group-map group-name="org.ofbiz.olap" datasource-name="localmysqlolap"/>  
   <group-map group-name="org.ofbiz.tenant" datasource-name="localmysqltenant"/>  
 </delegator>

Save the file.

Step 5: Installing Apache OFBiz

 # cd /opt/apache-ofbiz/  
 # ./ant

Step 6: Install Dataset, Load Demo and Seed Data

Apache OFBiz provides dataset, demo data and seed data, this data is useful for experiment. This data is unuseful for production setup.

 # ./ant load-demo  
 # ./ant load-extseed

Step 7: Start Apache OFBiz Service

After installing Apache OFBiz, Use following command to start Apache OFBiz service on system.

 # ./ant start

Access Apache OFBiz in Browser

Access Apache OFBiz in browser on port 8443 as below given url and login credentials.

 URL: https://svr10.tecadmin.net:8443/myportal/control/main  
 Admin Username: admin  
 Admin Password: ofbiz

References:

http://ofbiz.apache.org/

Congratulation’s! You have successfully install apache OFBiz with Mysql integration on your Linux system.

How to Install JAVA 8 (JDK 8u45) on Ubuntu & LinuxMint Via PPA

2015-08-06T22:54:00.000-07:00

This blog post will help you to Install Oracle JAVA 8 (JDK/JRE 8u25) on Ubuntu 14.04 LTS, 12.04 LTS and 10.04 and LinuxMint systems using PPA File.

Installing Java 8 on Ubuntu

Add the webupd8team Java PPA repository in your system and install Oracle Java 8 using following set of commands.

 $ sudo add-apt-repository ppa:webupd8team/java  
 $ sudo apt-get update  
 $ sudo apt-get install oracle-java8-installer

Verify Installed Java Version

After successfully installing oracle Java using above step verify installed version using following command.

 manish@tech:~$ java -version  
 java version "1.8.0_45"  
 Java(TM) SE Runtime Environment (build 1.8.0_45-b14)  
 Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

Configuring Java Environment

In Webupd8 ppa repository also providing a package to set environment variables, Install this package using following command.

 $ sudo apt-get install oracle-java8-set-default

Reference:-

https://launchpad.net/~webupd8team/+archive/ubuntu/java

ELK Stack: Collection and Analysis of Centralized Logs

2015-05-25T22:31:00.000-07:00

As a DevOps, it is very difficult to identify, collect and process the logs which could of System logs, Web server logs etc.

The one of the solution of above problem could be ELK stack.

ELK stack mainly composed of 3 components:

Elasticsearch: Store the logs collected from different servers
Logstash: Collect all types of logs at centralized location
Kibana: Runs the searchs and generate visual dashboard

How ELK works ?

Logstash is an open source tool for collecting, parsing, and storing logs for future use. Kibana is a web interface that can be used to search and view the logs that Logstash has indexed. Both of these tools are based on Elasticsearch. All these together are called ELK Stack.

Using Elasticsearch as a backend datastore, and kibana as a frontend reporting tool, logstash as pipeline for storing, querying and analyzing your logs.

ELK Stack Setup has mainly four components:

Logstash: Server component which collects all the incoming logs
Elasticsearch: stores all the logs
Kibana: Web interface for searching and analysing logs
Logstash Forwarder: Installed on server from which logs need to be collected. It acts as an agent uses lumberjack networking protocol to communicate with logstash.

First requirement in order to setup ELK stack is to have java installed on the system.

It is recommended to run a recent version of Java in order to ensure the greatest success in running Logstash.

It’s fine to run an open-source version such as OpenJDK:http://openjdk.java.net/
Or you can use the official Oracle version:http://www.oracle.com/technetwork/java/index.html

Install Elasticsearch

Run the below command to get repo from apt

 sudo wget -O - http://packages.elasticsearch.org/GPG-KEY-elasticsearch | sudo apt-key add -

Create the Elasticsearch source list

 sudo echo 'deb http://packages.elasticsearch.org/elasticsearch/1.1/debian stable main' | sudo tee /etc/apt/sources.list.d/elasticsearch.list

Update your apt package database:

 sudo apt-get update

Now, we have the source to download elasticsearch, give the below command to install it

 sudo apt-get -y install elasticsearch=1.1.1

Once, it is installed, we need to add below line to /etc/elasticsearch/elasticsearch.yml, to disable dynamic scripts.

script.disable_dynamic: true

In order to restrict the outside access to Elasticsearch instance(9200) by specifing the below line in configuration file.

network.host: localhost

If you want to access you Elasticsearch instance from clients on a different IP address via Javascript, add the following inside elasticsearch.yml

http.cors.enabled: true
http.cors.allow-origin: "*"

Once you are done with changes, save the file and restart the service

 sudo service elasticsearch restart

In order to boot up the Elasticsearch

 sudo update-rc.d elasticsearch defaults 95 10

Now your Elasticsearch is all set to store for your log from multiple servers.

Testing Elasticsearch:

Use the below commands to test the working of elasticsearch

 ps aux | grep elasticsearch  
 curl -X GET 'http://localhost:9200'  
 curl 'http://localhost:9200/_search?pretty'

In Browser: http://localhost:9200/

Elasticsearch Kopf Plugin

The kopf plugin provides an admin GUI for Elasticsearch. It helps in debugging and managing clusters and shards. It’s really easy to install:

 sudo /usr/share/elasticsearch/bin/plugin -install lmenezes/elasticsearch-kopf

Below is the screenshot for your understanding:

Install Kibana

Use the below link to download the build to install kibana

 sudo wget https://download.elasticsearch.org/kibana/kibana/kibana-3.0.1.tar.gz

Extract the build,

 sudo tar xvf kibana-3.0.1.tar.gz

Now, we need to open the kibana configuration to specify the port for elasticsearch from 9200 to 80, so we will later setup proxy server which could be nginx or squid etc. to redirect all request from port 80 to 9200. See below line in location ~/kibana/config.js

elasticsearch: "http://"+window.location.hostname+":80",

This is necessary as kibana will be running on 80 port.

Since, we are going to install nginx, we need to specify particular location for kibana say.

/opt/kibana3/

Copy all the contents to this location:

 cp -R ~/kibana/* /opt/kibana3/

Now, we hava setup the kibana, as discussed we need to install nginx, which is pretty easy.

Install Nginx

Use below command to install nginx

 sudo apt-get install nginx

Next, download the Nginx configuration from kibana's github repositories to your home dir.

 sudo wget https://gist.githubusercontent.com/thisismitch/2205786838a6a5d61f55/raw/f91e06198a7c455925f6e3099e3ea7c186d0b263/nginx.conf

In above configuration we need to specify the FQDN (Fully Qualified Domain Name), and Kibana's root directory.

server_name FQDN;
root /root/kibana3;

Once you are done with changes move the file to nginx configuration location

 sudo cp nginx.conf /etc/nginx/sites-available/default

In order to improve your security to access nginx, you can apache2-utils to use htpasswd to generate username and password.

 sudo apt-get install apache2-utils  
 sudo htpasswd -c /etc/nginx/conf.d/kibana.htpasswd user

Now, you can restart the nginx service for the changes to take effect.

Kibana is now accessible via your FQDN or the public IP address of your Logstash Server i.e. http://logstash_server_public_ip/. If you go there in a web browser, you should see a Kibana welcome page which will allow you to view dashboards but there will be no logs to view because Logstash has not been set up yet. Let's do that now.

Install Logstash

The Logstash package is available from the same repository as Elasticsearch. As public key is already setup, let's create the source list

 sudo echo 'deb http://packages.elasticsearch.org/logstash/1.4/debian stable main' | sudo tee /etc/apt/sources.list.d/logstash.list

Update your apt package database

 sudo apt-get update

Install the logstash using below command:

 sudo apt-get install logstash=1.4.2-1-2c0f5a1

Generate SSL certificates:

Since we are going to use Logstash Forwarder to ship logs from our Servers to our Logstash Server, we need to create an SSL certificate and key pair. The certificate is used by the Logstash Forwarder to verify the identity of Logstash Server. Create the directories that will store the certificate and private key with the following commands:

 sudo mkdir -p /etc/pki/tls/certs  
 sudo mkdir /etc/pki/tls/private

If you have a DNS setup with your private networking, you should create an A record that contains the Logstash Server's private IP address—this domain name will be used in the next command, to generate the SSL certificate. Use the below command to generate it:

 sudo cd /etc/pki/tls; sudo openssl req -subj '/CN=logstash_server_fqdn/' -x509 -days 3650 -batch -nodes -newkey rsa:2048 -keyout private/logstash-forwarder.key -out certs/logstash-forwarder.crt

Since, ssl certificate is generated, we need to transfer it to server from which we are going to ships logs to logstash.

Configure Logstash

Now, lets configure the logstash so that kibana can get the log from it.

Logstash configuration files are in the JSON-format, and reside in /etc/logstash/conf.d. The configuration consists of three sections: inputs, filters, and outputs.

Let's create a configuration file called 01-lumberjack-input.conf and set up our "lumberjack" input (the protocol that Logstash Forwarder uses):

Create a file at location /etc/logstash/conf.d/01-lumberjack-input.conf

which contains

input {
lumberjack {
port => 5000
type => "logs"
ssl_certificate => "/etc/pki/tls/certs/logstash-forwarder.crt"
ssl_key => "/etc/pki/tls/private/logstash-forwarder.key"
}
}

Now let's create a configuration file called 10-syslog.conf, where we will add a filter for syslog messages at location /etc/logstash/conf.d/10-syslog.conf

filter {
if [type] == "syslog" {
                                        grok {
                                                    match => { "message" => "%                         {SYSLOGTIMESTAMP:syslog_timestamp} %{SYSLOGHOST:syslog_hostname} %     {DATA:syslog_program}(?:\[%{POSINT:syslog_pid}\])?: %{GREEDYDATA:syslog_message}"                                                     }
                                            add_field => [ "received_at", "%{@timestamp}" ]
                                            add_field => [ "received_from", "%{host}" ]
                                            }
                                            syslog_pri { }
                                            date {
                                            match => [ "syslog_timestamp", "MMM d HH:mm:ss", "MMM dd HH:mm:ss" ]
                                                   }
                                        }
     }

This filter looks for logs that are labeled as "syslog" type (by a Logstash Forwarder), and it will try to use "grok" to parse incoming syslog logs to make it structured and query-able at location /etc/logstash/conf.d/30-lumberjack-output.conf

output {
elasticsearch { host => localhost }
stdout { codec => rubydebug }
}

This output basically configures Logstash to store the logs in Elasticsearch.

With this configuration, Logstash will also accept logs that do not match the filter, but the data will not be structured (e.g. unfiltered Nginx or Apache logs would appear as flat messages instead of categorizing messages by HTTP response codes, source IP addresses, served files, etc.).

Now Restart the logstash to make changes take effect:

 sudo service logstash restart

Setup Logstash Forwarder Package:

Get the SSL certificate which we generated previously to server from which we get the logs

 sudo scp /etc/pki/tls/certs/logstash-forwarder.crt user@server_private_IP:/tmp

Install Logstash-forwarder Package:

On Server, create the Logstash Forwarder source list:

 sudo echo 'deb http://packages.elasticsearch.org/logstashforwarder/debian stable main' | sudo tee /etc/apt/sources.list.d/logstashforwarder.list

It also uses the same GPG key as Elasticsearch, which can be installed with this command:

 sudo wget -O - http://packages.elasticsearch.org/GPG-KEY-elasticsearch | sudo apt-key add -

Then install the Logstash Forwarder package:

 sudo apt-get install logstash-forwarder

Next, you will want to install the Logstash Forwarder init script, so it starts on bootup:

 sudo cd /etc/init.d/; sudo wget https://raw.githubusercontent.com/elasticsearch/logstash-forwarder/a73e1cb7e43c6de97050912b5bb35910c0f8d0da/logstash-forwarder.init -O logstash-forwarder  
 sudo chmod +x logstash-forwarder  
 sudo update-rc.d logstash-forwarder defaults

Now copy the SSL certificate into the appropriate location (/etc/pki/tls/certs):

 sudo mkdir -p /etc/pki/tls/certs  
 sudo cp /tmp/logstash-forwarder.crt /etc/pki/tls/certs/

Configure Logstash Forwarder:

We need to specify in logstash forwarder configuration details of the logstash server so that it can send the details to server.

Now add the following lines into the file, substituting in your Logstash Server's private IP address for logstash_server_private_IP at location /etc/logstash-forwarder:

{
        "network": {
                            "servers": [ "logstash_server_private_IP:5000" ],
                            "timeout": 15,
                            "ssl ca": "/etc/pki/tls/certs/logstash-forwarder.crt"
                        },
        "files": [
                    {
                    "paths": [
                                    "/var/log/syslog",
                                    "/var/log/auth.log"
                                    ],
                    "fields": { "type": "syslog" }
                    }
                ]
}

Now, restart the logstash forwarder using below command

 sudo service logstash-forwarder restart

Now, we have setup ELK stack, we just need to check the kibana dashboard for more details.

Below are the useful screenshots which represents the data which we got from server.

Conclusion:-

The ELK stack is very useful in different manners as in this case you will find almost all the logs that could be application log, webserver log, system log etc. Using kibana, will have a visualize report which shows the analysis of the logs which is very helpful to extract the required information.

The ELK stack is easy to maintain on the large scale systems and and large scale infrastructure.

Configure S3 bucket to enable CORS configuration

2015-05-24T09:12:00.002-07:00

In order to configure s3 to allow cross-origin sharing, we need to create CORS configuration, xml document with rules that identify the origins that will allow to access your bucket, the operation(HTTP methods) will support for each origin according to configuration mentioned in S3.

In CORS configuration, you can specify following values for the AllowedMethod element.

GET
PUT
POST
DELETE
HEAD

While defining we must understand the following rules:

First we need to specify the AllowMethod (GET, PUT, DELETE Etc) request on the first origin . The rule also allows all headers in a preflight OPTIONS request through the Access-Control-Request-Headers header.
Same rules in applied on another origin
The third rule allows cross-origin GET requests from all origins. The '*' wildcard character refers to all origins.

Configuring S3 bucket:

Within the properties of the bucket we have to choose the option “Edit CORS configuration”:

In the window that appears, enter a configuration like this:

This will accept any GET, PUT, POST or DELETE request for any element in the bucket, as long as the origin of the request is an element stored in a subdomain of example.com.

Technically, the bucket will respond to these requests with the header “Access-Control-Allow-Origin: *.example.com” when they are performed including the header Origin.

This way you can configure the s3 to enable the CORS configuration.

CORS:- Cross Origin Resource Sharing

2015-05-10T00:29:00.001-07:00

Earlier, developers having the difficulty in order to make a request to a different domain from javascript. Everyone setup proxies on their websites, which was one of the onset of a new host of open redirect problems, as a way to get around the restriction. Although developers were working around this limitation using server-side proxies as well as number of techniques.

Almost all browser now support CORS (Includes IE 8+, Firefox 3.5+, Chrome)

Cross-Origin Resource Sharing (CORS)

* It is W3C Working draft that defines how the browser and server must communicate when accessing sources across origin. It is specification recommended by the Web Applications Working Group within the W3C.It provides a way for script running in clients browsers to use the XMLHttpRequest API object and make direct HTTP Requests to resources on domains other than from where the script was first loaded. say Zuora REST API.

* CORS provides following features:
Guarantees the data integrity of the API request- Nothing chenaged on its way from your server to customer.
Provides authentication - ensures that the person who generated the request is who they say they are.
The Basic idea behind CORS is to use custome HTTP headers to allow both the browser and the server to know enough about each otherin order to determine if the request or response should suceed or fail.

For a simple request, one that uses either GET or POST with no custom headers and whose body is text/plain, the request is sent with extra header called Origin, The Origin header contains the origin (protocol, domain name, and port) of the requesting page, in order to make the request to serve.

An example Origin header looks like:

 Origin: http://www.domainA.com

If the server decides that the request should be allowed, it sends a Access-Control-Allow-Origin header echoing back the same origin that was sent or "*" if it's a public resource. Say,

 Access-Control-Allow-Origin: http://www.domainB.net

This way we can do sharing of resources against different origin.

MongoDB: Installation on Ubuntu/Debian Machine

2014-08-17T02:27:00.001-07:00

Before making an installation of Mongodb on ubuntu we need to add sources list to local repository.
First of all, we need to add MongoDB Public GPG Key

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 7F0CEB10

Next, we need to update source list /etc/apt/source.list.d/mongodb.list file using following command

echo 'deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen' | sudo tee /etc/apt/sources.list.d/mongodb.list

Now, we need to update the repository...

sudo apt-get update

Now , we are ready to install our MongoDB installation

apt-get install mongodb-10gen=2.2.3

Now we had installed MongoDB , we need to start the service

service mongodb start

To login into mongodb prompt, we give command

mongo

If you need mongodb help, use command

db.help()

Jenkins: Installation on Ubuntu/Debian Machine

2014-07-06T07:48:00.000-07:00

Installing Jenkins on Ubuntu or Debian

* If you are installing Jenkins on Debian or Ubuntu, it is convenient to install the native binary package for these platforms. So. First of all, you need to add the key to your system as below:
$ wget -q -O - http://pkg.jenkins-ci.org/debian/jenkins-ci.org.key | apt-key add -

$ sudo echo "deb http://pkg.jenkins-ci.org/debian binary/" > /etc/apt/sources.list.d/jenkins.list

* Now, we update the Debian package repository, to check whether key is set and package are easily extracted.
$ sudo apt-get update -y

* Once this is done, you can install Jenkins using apt-get tool:
$ sudo apt-get install -y jenkins

This will install jenkins as a service, with a correclty configured script at /etc/init.d/jenkins and a corresponding system user called "jenkins".

* By default, you will find the jenkins WAR file in the /usr/share/jenkins directory, and the Jenkins home directory in /var/lib/jenkins.

* Now, you can start the Jenkins service:
$ sudo /etc/init.d/jenkins start
or
$ sudo service jenkins start
* You can see the Jenkins dashboard at http://localhost:8080/
If you can see the dashboard that means you have correct installation on Debain/Ubuntu

This is way to install to Jenkins on Debian/Ubuntu Machine. Other Machines (REDHAT, CentOS) will require some changes.

JAVA: How to install Java (JRE/JDK) on Ubuntu Machine

2014-07-06T07:28:00.001-07:00

Installing default JRE/JDK
This is recommended and will install OpenJDK 6 on Ubuntu 12.04 and earlier and on 12.10+ it will install OpenJDK7.

* Installing java with apt-get is easy. First update the package
sudo apt-get update -y

* Then, check Java is installed or not
java -version
If it returns "The program java can be found in the following packages" then you need to install it. For that you need to execute following command:
sudo apt-get install default-jre

This install Java Runtime Environment(JRE)

* Now you will also need Java Development Kit (JDK) needed to compile Java applications(say Apache Ant , Apache Maven, Eclipse).
Execute the following command:
sudo apt-get install default-jdk

This is everything need to install Java on Ubuntu Machine.

Chef solo: Chef Installation and create first cookbook

2014-07-03T11:03:00.000-07:00

Install curl for installing chef
apt-get install curl*

Installing chef using curl
curl -L https://www.opscode.com/chef/install.sh | bash
You can choose the chef install link from according to your OS.
http://www.getchef.com/chef/install/

Checking chef is installed or not or verifing the installation
chef-solo -v

Now you need to get the file structure of chef in order to organise the various cookbooks
wget http://github.com/opscode/chef-repo/tarball/master
tar zxf master
mv opscodee-chef-repo* chef-repo

Now to get to start writing cookbook for apache
cd chef-repo
mkdir .chef

We use knife cli tools to create cookbooks . First we need to tell knife where to fetch the cookbook
echo "cookbook_path [ '/root/chef-repo/cookbooks' ] " > .chef/knife.rb

Now we will create a phpapp cookbook
knife cookbook create phpapp
cd cookbooks

Now we download cookbook which acts a library for our cookbook
Apache2
knife cookbook site download apache2
tar zxf apache2*

Apt - which ensure that chef-solo mkaes a apt-get update before we install any packages.
knife cookbook site download apt
tar zxf apt*
Iptables

knife cookbook site download iptables
tar zxf iptables*

Logrotate -
knife cookbook site download logrotate
tar zxf logrotate*
Pacman
knife cookbook site download pacman
tar zxf pacman*

Now we configure these things
cd phpapp/

Now we need to make changes in different configuration files
open metadata.rb
add line
depends "apache2"

Open recipe/default.rb add lines

include_recipe "apache2"

         apache_site "default" do

              enable true

         end

cd ../..
create a file solo.rb and add lines
file_cache_path "/root/chef-solo"
cookbook_path "/root/chef-repo/cookbooks"

Again create a file name web.json
add lines

 {

         "run_list" :   ["recipe[apt]", "recipe[phpapp]"]

      }

Now finally execute below command to run the code
chef-solo -c solo.rb -j web.json

Note: using Ubuntu machine as OS in rackspace

Knife-solo: CLI tool for chef

2014-07-03T10:32:00.002-07:00

knife-solo adds a handful of Knife commands that aim to make working with chef-solo as powerful as chef-server.

Usage: Having the gem installed will add knife chef subcommands.

Run knife solo with no arguments to know all the commands.

Knife-solo is a command-line tool that provides an interface between a local chef-repo and chef-server.
It include 5 subcommands to knife tools:
* knife solo init myapp: This will create a chef standard directory (i.e. kitchen) structure which will be used for build and store recipes. It's like initialising
* knife solo prepare: Installs chef on a given host. It auto detect the targeted OS.
* knife solo cook: Uploads the kitchen to target host and run chef-solo.
* knife solo bootstrap: combines the two previous ones.
* knife solo clean: removes the uploaded kitchen from the target host.

This actually helps you create a directory structure of chef and also it integrates with Berkshelf and Libraian-Chef and bootstraps the process of the nodes.

Ruby On Rails Installation using RVM (Ubuntu)

2014-04-18T13:48:00.001-07:00

For the installation of ruby on rails follow below steps

* Ruby Version Manager: Firstly, we need to install ruby version manager.

$ apt-get install curl

$ \curl -sSL https://get.rvm.io | bash -s stable

$ source ~/.rvm/scripts/rvm

* Ruby: Next, Once you are using RVM , we need to install ruby

$ rvm install 2.1

you can make the recently installed ruby version as default as there may be more than one ruby installed.

$ rvm use ruby --default

* Rubygems: The next step is to install rubygems with current version/

$ rvm rubygems current

* Rails: Once everything is setup, it's time to install rails

$ gem install rails

This is how, the ruby on rails get installed on your ubuntu machine.

SSH Keygen: Is RSA or DSA Better

2014-01-19T01:50:00.006-08:00

Here are some of the points to be considered:

* DSA is faster for signature generation but slower for validation, slower when encrypting but faster when decrypting and security can be considered equivalent compared to an RSA key of equal key length.
* The Security of the RSA algorithm is based on the fact that factorization of large integers is known to be "difficult" whereas DSA security is based on the discrete logarithm problem.
* Today, Fastest known algorithm for factoring large integers is the General Number Field Sieve, also fastest algorithm to solve the discrete logarithm problem in finite fields modulo a large prime p as specified for DSA
* In RSA, we don't ever need a secure random number generator to create signatures whereas, DSA needs a value that has to be random, secret/unpredictable and can never be used.
* RSA keys can go up to 4096 bits, where DSA has to be exactly 1024 bits (although OpenSSL allows for more)

Things in favor of DSA

1. DSA can only be used with SSH protocol 2 while RSA can be used with protocols 1 and 2 (See “SSH 2″ Versus “OpenSSL and OpenSSH Release 2”). Protocol 1 has some significant design flaws and has been replaced by Protocol version 2. I see this as a reason to slightly favor using DSA keys, a sort of built in protection from using the older obsolete protocol.

Things in favor of RSA
1. A bad random number generator will leak DSA key bits
2. The openssh.org web site appears to be mute on the subject of which is better, but the newer versions of ssh-keygen create an RSA key if you do not specify the type
3. There seem to be more (and newer) RFCs referencing RSA keys than DSA keys.

Shebang

2013-07-07T01:50:00.002-07:00

In computing, a shebang, when it occurs as the initial two characters on the initial line of a script, is the character sequence consisting of the characters number sign and exclamation mark (“#!”).

Syntax:-

The form of a shebang interpreter directive is as follows:

#! Interpreter [optional - arg]

The interpreter must usually be an absolute path to a program that is not itself a script. The optional – arg should either not be included or it should be a string that is meant to be a single argument

Some typical shebang lines:

Ø #!/bin/sh – Execute the file using sh, the Bourne shell, or a compatible shell

Ø #!/bin/csh –f – Execute the file using csh, the C shell

Ø #!/usr/bin/perl –T – Execute using Perl with the option for taint checks[‘feature which increase security by preventing malicious users from executing commands on a host computers.’]

Ø #!/usr/bin/php – Execute the file using the PHP command line interpreter.

Ø #!/usr/bin/python –O – Execute using Python with optimizations to code

Ø #!/usr/bin/ruby – Execute using Ruby

Another and more preferred way is:

#!/usr/bin/env python

Python IDEs

2013-05-16T16:18:00.001-07:00

Eclipse and PyDev

Eclipse is an advanced open-source IDE GUI. Originally developed as a Java IDE. It also support python Development when PyDev plugin is installed. Eclipse is a powerful and popular option for Python development which includes support for code completion, syntax highlighting, syntax analysis, refactoring and debugging and more. Its downsides it that it is large system to install and may require shareware extensions for some features.

Komodo

A full-featured environment for Python development . it includes standard syntax-coloring, text-editing, debugging and other features. It also offers many features which includes project files, source-control integration, regular-expression debugging, and drag-and-drop GUI builder that generates Python/tkinter code to implement the GUIs you design interactively. It Is Multi-language IDE with support for Python 2.x and Python 3 and works on Windows/Linux/Mac OS X Platforms.

NetBeans IDE for Python

NetBeans is a powerful open-source development environment GUI with support for many advanced features say code completion, code refolding, refactoring, debugging, code coverage and testing, projects and more. It may be used for CPython and Jython code development. Platform: Linux, Mac, Solaris, Windows.

For more info:- http://wiki.netbeans.org/Python

Python Win

It is a free Windows-only IDE for python that ships as part of Active’s State Active Python distribution. It is roughly like IDLE with a handful of useful Window –specific extension added.

For more info:- http://sourceforge.net/projects/pywin32/

Wing IDE

Wing IDE is a powerful development environment for python programming language. It has a code browser, syntax coloring, code completion, call tips and other code intelligence features. There is also a full-featured editor with optional emacs key bindings and powerful debugging tools. Wing IDE allow you to debug CGI scripts. Python code running under Zope and Plone, embedded python code and stand-alone applications. It has two levels: -Wing IDE Pro and Wing IDE Personel.

For more info :- http://www.wingware.com/

2013-02-27T11:07:00.000-08:00

Event Report: An Introduction on Robotics and its application

A workshop was organised jointly by USIC and LMC on Robotics during 18^th-21^st February 2013

On First day, A quick inauguration session was organised led by J.R Bishnoi (USIC) and then there is lecture by Mr. K.R. Chowdhary on the introduction to Robotics and then there is lecture on Introduction on Electronics by Mrs. Veena Bhatia.

These two lecture gives us the quick revision of the basics of the robotics and Electronics.

On Second Day, there is 2 quick lecture. One of them is on Concept of microcontroller by Dr. Mukesh Upadhyay and then there is lecture by Mr. Alok singh gehlot who demonstrated the type of robots which he created and that can be created by others. Then there is some practicals organised by Mr Gunjan Mathur.

These lectures demonstrated of the kind the robots that can be created using microcontrollers and what are component will be need for them.

On the Third Day, there is 2 lecture based on the microcontroller and robotics with its application by Dr. Mukesh Upadhyay and Mr. Alok singh gehlot .

These lectures give us the complete knowledge microcontrollers and details of their components.

On the fourth day, there is last session by Mr. Rajesh Purohit who shows the classification of Robotics parts (Sensors, Actuators etc) and then there is closing ceremony which was led by Mr. R.L.Mathur (Principal LMC).

Thanks to the Organising committee for organising such an event..

Photo-set of the event is available here....

C# - How it's all about

2013-01-28T07:24:00.000-08:00

· C# is one of the languages used to create applications that rum in .NET CLR.

It is an evolution of the C and C++ languages and has been created by Microsoft to work with the .NET platform.

· Developing applications using C# is simpler than using C++, because the language syntax is simpler.

· C# is a powerful language, as those features of C# parallel the features of C++ such as directly accessing and manipulating system memory, can only be carried out using code marked as unsafe.

· C# code is slightly more verbose than C++. This is a consequence of C# being a type-safe language.

DOT NET: How it works:

2013-01-25T07:22:00.001-08:00

Application code is written using a .NET – compatible language language such as C#

T That code is compiled into MSIL, which is stored in an assembly.

When this code is executed (either in its own right if it is an executable or when it is used from other code), it must first be compiled into native code using a JIT compiler

The native code is executed in the context of the managed CLR, along with any other running applications or processes.

Release Coordinator in DevOps

2012-12-26T06:40:00.004-08:00

A relatively new role in enterprise IT which is primarily tasked with coordinating deployments of enterprise software to pre-production environments. The need for the release coordinator has been driven by:

· The need to fill the DevOps “gap”

· Increased infrastructure complexity - multiple layers and platforms which form web applications.

· Growth in rate of release – due to agile and iterative development.

· Distributed teams – globally deployed, outsourced and hybrid environment, testing and infrastructure teams.

The release co-ordinator role (referred to as a deployment or integration co-ordinator) has emerged from the release management or release engineering teams. This role is similar to an air traffic controller - performing real time co-ordination activities across diverse teams to achieve a group goal using shared resources .

Release co-ordination contrast with release management, which is often focused on planning and reporting on software changes, in order to control the release of specific application changes into production. Release engineering is concerned with the systematic and technical work related to building and deployment code into enviroments.

Characteristics of DevOps:

2012-12-26T06:19:00.001-08:00

1 Ability to write code beyond simple scripts.

2. Focus on stability and uptime.

3. Extra focus on moving between states :-

In dev land, I have situations when the end result of a particular feature was analysed on its ow merit, without taking into consideration how a system can be moved from its desired future state. DevOps pays extra attention to this problematic area.

4. Different angle on business revenue : -

While developers usually work on things that are meant to increase or sustain business revenues, devops often work on things that are meant to prevent or reduce loss of business revenues

5. In devops, we are users of our own software .

6. Architect, developers, tester, product manager, project manager – all in one.

7. Awareness of normal accidents.

8. Quality Assurance in production.

9. Manual First, then Automate

10. Almost always distributed or hyper-distributed.

DevOps: New face of software development.

2012-12-26T06:14:00.002-08:00

It is a software development method that stresses communication, collaboration and integration between software developers and information technology professionals.

Src:-http://en.wikipedia.org/wiki/DevOps

DevOps is a response to the growing awareness that there is disconnect between what is traditional considered development activity and what is traditional considered operations activity. This disconnect often manifests itself as conflict and inefficiency.

As there is a “Wall Of confusion ” between development and operations . This “Wall” is caused by a combination of conflicting motivations, processes, and tooling.

Src:-http://www.somic.org/2010/03/02/the-rise-of-devops/

Development-centric folks tend to come from a mindset where change is the thing that they are paid to accomplish. The business depends on them to respond to changing needs. Because of this relationship, they are often incentivized to create as much change as possible.

Operations folks tend to come from a mindset where change is the enemy. The business depends on them to keep the lights on and deliver the services that make the business money today. Operations is motivated to resist change as it undermines stability and reliability.

Pik: Ruby Version Management on Windows

2012-11-28T21:08:00.001-08:00

Pik:
http://rubyinstaller.org/add-ons/pik/

'via Blog this'

HTML Images:

2012-08-10T01:30:00.000-07:00

Insert image – The <img> Element:

You will insert any image in tour web page by using <img> tag. Following is the simple syntax to use this tag.

Image Attributes:

Following are most frequently used attributes for <img> tag.

· Width: sets width of the image. This will have a value like 10 pr 20% etc.

· Height: sets height of the image. This will have a value like 10 or 20% etc.

· Border: sets a border around the image. This will have a value like 1 or 2 etc.

· Src: specifies URL of the image file.

· Alt: this is an alternate text which will be displayed if image is missing.

· Align: this sets horizontal alignment of the image and takes value either left, right or center.

· Valign: this sets vertical alignment of the image and takes value either top, bottom or center.

· Hspace: horizontal space around the image. This will have a value like 10 or 20% etc.

· Vspace: Vertical space around the image. This will have a value like 10 or 20% etc.

· Name: name of the image with in the document.

· Id: id of the image within the document.

· Style: this will be used if you are using CSS.

· Title: specifies a text title. The browser, perhaps flashing the title when the mouse passes over the link.

· ismap and usemap: These attributes for the <img> tag tell the browser that the image is a special mouse-selectable visual map of one or more hyperlinks, commonly known as an image map.

HTML Marquees

2012-08-10T01:29:00.002-07:00

A HTML marquee is a scrolling piece of text displayed either horizontally across or vertically down your web site page depending on the settings. This is created by using HTML tag <marquee>.

Syntax:

A simple syntax to use marquee is as follows:

One or more lines or text message or image.

</marquee>

Attributes:

A HTML marquee can have following attributes:

· Width: how wide the marquee is. This will have a value like 10 or 20 % etc.

· Height: how tall the marquee is. This will have a value like 10 or 20%etc.

· Direction: which direction the marquee should scroll. This will have value either up, down, left or right.

· Behaviour: what type of scrolling. This will have value scroll, slid and alternate.

· Scrolldelay: how long to delay between each jump. This will have a value like 10 etc.

· Scrollamount: how far to jump. This will have a value like 10 etc.

· Loop: how many times to loop. The default value is INFINITE, which names that the marquee loops endlessely.

· Bgcolor: background color. This will have a value like 10 or 20% etc.

· Vspace: vertical space around the marquee. This will have a value like 10 or 20% etc.

· Hspace: horizontal space around the marquee. This will have a value like 10 or 20% etc.

HTML Comments

2012-08-10T01:29:00.000-07:00

Comments are piece of code which is ignored by an web browser. It is good practice to comment your code, especially in complex documents, to indicate sections of a document, and any other notes to anyone looking at the code.

HTML Comment lines are indicated by the special beginning tag <!—and ending tag --> placed at the beginning and end of EVERY line to be treated as a comment.

Comments do not nest, and the double-dash sequence “--” may not appear inside a comment except as part of the closing --> tag. You must also make sure that there are no spaces in the start-of-comment string.

For example: Given line is a valid comment in HTML.

But following line is not a valid comment and will be displayed by the browser. This is because there is a space between the left angle bracket and the exclamation mark.

Multiline Comments:

You have seen how to comment a single line in HTML. You can comment multiple lines by the special beginning tag  placed before the first line and end of the lastline to be treated as a comment.

For example:

<!--

This is a multiline comment <br />

And can span through as many as lines you like.

-->

Conditional Comments:

Conditional comments only work as follows:

<!—[if IE 6]>

Special instructions for IE 6 here

<![endif]-->

· Their basic structure is the same as an HTML comment (). Therefore all other browsers will see them as normal comments and will ignore them entirely.

· Explorer Windows, though, has been programmed to recognize the special <!—[if IE]> syntax, resolves the if and parses the content of the conditional comment as if it were normal page content.

· Since conditional comments use the HTML comment structure, they can only be included in HTML files.

Using Comment tag:

There are few browsers who supports <comment> tag to comment a part of code.

<p>This is <comment> not </comment> Internet Explorer. </p>

Commenting Scripts and Style Sheets:

If you are using Java script or VB in your HTML code then it is recommended to put that script code inside proper HTML Comments to make old browser works properly.

For example:

<!—

Document.write(“Hello World!”)

//-->

</script>

Similarly if you are using Casecading Style Sheet in your HTML code then it is recommended to put that style sheet code inside proper HTML Comments to make old browser works properly.

For example:

<style>

<!—

Img{

Border:0px;

}

</style>