Welcome to


Rohit Mehta : A Linux Follower

bangalore, Karnataka, India
hi! i m a person who is chill all time. Since jan 2008 i am working for Novell software. The word Impossible does not exist in my dictionary because Impossible says i m possible...hey guys have fun with linux...it begins but has no end......

Saturday, November 21, 2009

LDAP, Lightweight Directory Access Protocol


LDAP, Lightweight Directory Access Protocol, a directory service internet protocol runs over Transmission Control Protocol/internet Protocol (TCP/IP) that that email and other programs use to look up information from a server.
Every email program has a personal address book, but how do you look up an address for someone who’s never sent you email? How can an organization keep one centralized up-to-date phone book that everybody has access to?
That question led to development of a standard called DIRECTORY SERVICES which supports the capability to locate certain types of information easily, efficiently, and quickly.
A directory is a set of objects with attributes organized in a logical and hierarchical manner. A simple example is the telephone directory, which consists of a list of names (of either persons or organizations) organized alphabetically, with each name having an address and phone number associated with it.
For example, the entry for Rohit Mehta might have the following attributes:
cn: Rohit Mehta
mail: rohitmehta.linux@gmail.com
telephoneNumber: 9663399899
telephoneNumber: 080-40022300
roomNumber: 353

Lightweight Directory - Directories are kind of like a database but not really. A directory is a specialized
database that is optimized for lookups. Unlike a traditional RDBMS, LDAP is not designed to show
complex relationships between relations. Imagine if 99% of your actions on were going to be simple
"selects", and you wanted anyone, anywhere to be able to do these selects over the Internet. This is
where LDAP excels. Examples of directories are the TVGuide, the phone book, a library card
catalog, and DNS.

"Give me the phone number of John Smith."

"Give me all the tv shows that are on tonight on the Sci-Fi channel."

Access Protocol - LDAP is an outgrowth of the x.500 standard. LDAP is an open standard,
unlike many other proprietary directory solutions. Most of the directory-like solutions that were
out on the market are now very similar to LDAP. Some of these solution providers, Sun and
 Microsoft specifically, have designed JNDI and ADSI APIs so that you can connect with any
 kind of directory service. This is kind of like ODBC or JDBC is to an RDBMS.
Cool things you can do with LDAP
-Contact Management

-Users and Security

-Image storage

-Document Management

-Store business logic - actual code or SQL statements

Tuesday, November 17, 2009

The Future Is Here


What is a zombie process???

zombieZombie process is a process observed in Unix/Linux operating system. Zombie process are those process which has finished execution but still have an entry in the process table. This entry for the zombie process is used by the parent to know about the exit status of its child .

After the zombie is removed, its process id and entry in the process table can then be reused but until its entry is in the process table that value cannot be used for other process in case the parent spawns the new process. It will allocate a new pid different from that of zombie process to the new process created.
Zombies can be identified in the output from the ps command in Linux by the presence of a “Z” in the “STAT” column.
To remove zombies from a system, the SIGCHLD signal can be sent to the parent manually, using the kill command. If the parent process still refuses to reap the zombie, the next step would be to remove the parent process. When a process loses its parent, init becomes its new parent. Init periodically executes the wait system call to reap any zombies with init as parent.

How does SSH(Secure Shell) works

You must have done remote file sharing and remote logins. Have you ever thought that whether your communication over the channel  is   secure or not. If you are using tools/utilities like ftp , telnet then you are not secure. SSH acronym for Secure Shell enables you to have transfer over the network in the encrypted manner.
This is how SSH works:
When a user attempts for a remote login using SSH ,for the first time it prompts for the generation of keys. SSH uses asymmetric Encryption. Asymmetric encryption also allows for digital certificates.

Two types of key are generated:
Private key : This key is kept only with the user who generated the key and is used for encrypting the messages before sending them over the network.
Public key : This key is distributed to all the users with which you want to encrypt your communication .Remote system uses this key to decrypt the encrypted messsages which is sent by the user to the remote  machines.
This is how SSH actually works:
generate public/private key pair : P and S
 publish public key P .guard private key S
encrypt message M with private key S
 send recipient S(M)
decrypt with sender’s public key to recover M=P(S(M))
For making remote login through ssh :
At the hash prompt:
then type yes for the generation of the keys and then enter the password for the remote system and you are logged into the system
Enjoy the encrypted communication and stay away from network hacks.

Error message : device or resource busy


You may have encountered the error message:
Cannot open /dev/hda9 : device or resource busy
in linux many times..where /dev/hda9 is one of your partitions of your hard drive /dev/hda..and 9 is the partition number.
This can happen due to one of the following reasons:-
1.The device could be mounted somewhere.To fix this

Check /etc/fstab file.
#cat /etc/fstab
We can see that the last line contains /dev/hda9 mounted on /quota folder.
Comment out this line
Open /etc/fstab file with your favourite editor..we will use vi editor here.
#vi /etc/fstab
Go in insert mode by pressing ‘i’ and comment out the line.
Move out of the editor with [esc] and then :wq
#umount /dev/hda9
#mount –a
Now check with,
You will not see /dev/hda9 mounted.
2.Another reason may be that the device you are trying to access (or use) is supposedly busy (in use) or that a resource it needs (such as an IRQ) is supposedly being used by another device and can’t be shared. This message is easy to understand if it only means that the device is busy (in use). But it sometimes means that a needed resource is already in use (busy). What makes it even more confusing is that in some cases neither the device nor the resources that it needs are actually “busy”.

What Is A Gravatar And How To Setup Gravatar Account

gravatarIn times one was afraid of giving his/her e-mail address on some blogs , forums ,and sites as he was afraid of spamming.
Tom Werner discovered the solution and what is known as gravatar. So what is a gravatar???
Gravatar short  for GLOBALLY RECOGNIZED AVATAR is aservice for providing globally-unique avatars. Gravatar, users can register an account based on their email address, and upload an avatar to be associated with the account.
To eliminate spam, e-mail addresses in gravatar are hashed with the Md5 cryptographic hash function.
Setting up an gravatar account:
It all starts when you sign up for a free account (and yes you do have to give a working email address as confirmation for your account setup is sent to it). Once you account is set up, you can upload your first avatar. Avatars can be uploaded from a hard drive, web address and even a webcam device. Once your avatar is uploaded, you will be asked to crop it (gravatar’s cropping tool is very flexible and easy to use) so it will look nice. After cropping and clicking on the “crop and finish!” button, a “select avatar rating” page will be shown. There you will be required to rate the avatar as one of the following:
0rated gravatar is suitable for display on all websites with any audience type.
1.jpgrated gravatars may contain rude gestures, provocatively dressed individuals, the lesser swear words, or mild violence.
2rated gravatars may contain such things as harsh profanity, intense violence, nudity, or hard drug use.
3rated gravatars may contain hardcore sexual imagery or extremely disturbing violence.
After selecting the rating  the following screen will appear and then click on the link “check this avatar” to get your confirmation and encrypted email-address.
For me it showed my encypted email id like this:
Address: emailid@yahoo.co.in
Hash: 2b3f0a93a608e3eb869554e46b3d71ad
Why do we use gravatar????
Gravatar acts as a  personal representations (or pictures) which help to distinguish one user from the next. If every user had the same default image, chaos could result and everyone would blend into a one color oceaning softwares.
Gravatar plugins are built in most of the blogging softwares. Wordpress  above 2.5 holds it and Redmine web based project management application beginning  with 8.0
have inbuilt feature for this application
For lower versions of wordpress and readmine  we manually need to download and install plugins.

Interesting Things You Should Know About BING

bingMicrosoft unveiled its search engine Bing. The Bing unveiling can surely be termed as one of the biggest Microsoft launches of the recent times considering the huge stakes it has in the company’s success.There is so much hype on the net about the new search engine Bing by Microsoft on the net that almost every blog has been covering it. Though I doubt anyone can take over Googlejust like that.With Internet gaining importance in the technology landscape, it has become critical for Microsoft to come out with a formidable player which can challenge Google’s growing dominance in the space.

So here are some things you should know about BING.

The Bing can verify any IP address and can tell you the name of the websites hosted on a particular IP ADDRESS

. To do that simply type,
IP:[ IP Address ]
in the bing search box.

The search result will display the sites hosted on that IP address.
Example type:
and you will see sites hosted on this ip address.

2.Remove the background Image on the Bing site

If you are not one of those eye-candy freaks, you can remove the background image on the Bing homepage. Instead of typing bing.com, you can navigate to the site using the following URL,
3.Bing outstripped Yahoo! almost immediately after its launch to take the No. 2 search engine spot.
4.unlike Google, Bing is not a search engine. The software giant dubs Bing as a “decision” engine, rather than a search engine. According to Microsoft, Bing is not just another search engine, but a decision engine that will help people in making decisions.
5.Interestingly, Bing doesn’t return any result for one of the most searched terms from India: sex. However, if you tell the search engine that you’re from the USA, or any one of the European countries (users can easily change country without even logging in), and bing, several links are returned. If you say you are from China or an Arabian country, or Hong Kong or Singapore, again, no luck.
6.Bing offers several features that are not automatically available on Google such as instant excerpts that allow users to see the contents of a page without actually clicking on it and a sidebar detailing related searches.
7.Bing Video seems to have become an instant hit, courtesy its thumbnail video feature. Try searching for a video on Bing Video, once the results appear just hover your mouse over the one you are keen on. Yes, the video starts playing instantly.
8.Another not-so-talked about Bing feature is Save and Share. The feature not only saves your search history, but also allows a user to refine it. Users can delete searches, go back to them, and most importantly save and share them.
9.Everyday, Bing features a different background image.

Which web browser has the least memory utilization

web-browsersThere must have been time when your system resources gets exhausted and the system  gets struck or hangs up.
In order to solve this problem we need to close the running applications or sometimes needs to do an abrupt shutdown.
Have you ever tried to find out the reasons for this problem.
There are many reasons for this problem:
Modern Web browsers are one of them
Firstly what is a web browser?
A Web browser is a software application that interprets the coding language of the World Wide Web and allows for retrieving ,traversing and presenting the information.

Web browsers
 utilize a lot of memory which contributes to increased response time.
So what to do..we cannot stop using them ,and only what we can do is select the best out of the many market’s web browser , which includes internet explorer, firefox , opera,netscape and many more.
Some tests were carried out by using browsers in similar condition and checking their memory utilization in MB which helps you to choose the best web browser.
The results were plotted on the graph with memory utilization (MB) ox horizontal-axis and browsers on the vertical axis.
So it proves the sluggishness of internet explorer and reasons for why to use firefox and opera.
New Firefox 3.5 RC 3 is even better then opera and its other compilants.
But what surprising is that still the major part of the world follow internet explorer.
I hope this article might give them something to think and boost their system performance.

Web Based Operating Systems:Take Your Desktop Inside Your Browser


rp_proEver wondered your desktop inside your browser.A full fledged operating system inside the browser.What if you could work with your files and documents anywhere around the world.A beautiful concept called web-based operating systems makes this possible.you just need to sign up and you are done,and just access the desktop anywhere.Below are some of the most popular web based operating systems.
A good place to start in your discovery of Web-based operating systems is eyeOS  , which is free, open source, and very easy to sign up for. There’s no need to install anything to use eyeOS. Simply sign up with a user name and password to create anaccount, and from that point forward, you have an operating system on the Web, accessible from any browser. eyeOS creates space on its servers to store your operating system settings and any files you create
This is how it looks

G.ho.st is in some ways even more full-featured and certainly more colourful – than eyeOS. After you sign up, for free, G.ho.st carves out an impressive 5 gigabytes of file storage on its servers for you, and it creates your very own G.ho.st Mail e-Mail account, with 3 gigabytes of storage. Like eyeOS, there’s nothing to install. Once you sign up, you’ll receive a confirmation e-Mail message. Click the activation link inside, and you’re ready to go

Desktop Two is a java-based Web operating system that’s the quickest of all to set up and get going. After a brief sign-up routine, the desktop loads, and you’re ready to start exploring. Desktop Two offers more applications that allow users to create their own presence on the Web than the other major Web operating systems. Along with a word processor and e-mail program, Desktop Two provides a Web site editor and a blogging programme
cmyos.com offers a free online operating system/desktop for all users through its open source collaborative network: cmynetworks. Through the open source community, cmyosworks to produce rich applications that are enhance the online experience of developersand browsers alike
cmy os
  • AstraNOS – Picture Windows 98. Then picture an OS X dock. Then picture a night sky. Then throw them all together. You now have a pretty good picture of AstraNOS.
  • BeDesk – Basic wrapper for other online tools
  • DoxBoard – Slick WebOS with some basic features
  • GCOE X – Nice WebOS with a powerful terminal and support for the iPhone
  • Glide – Online operating system with support for BlackBerry, Palm, Windows Mobile, Symbian and iPhone users
  • goowy – Great webtop with your own email account (@goowy.com), IM, 1GB of space (via Box.net), and much more
  • jooce – Slick invite-only online OS
  • mybooo – Invite-only webtop with a ton of features
  • myGoya – Nice WebOS with PIM features, a media player, and much more
  • OOS – Basic online operating system that offers a personal webpage
  • Parakey – Not much is known about Blake Ross’s newest invention, but we do know thatFacebook liked it enough to purchase it for an undisclosed sum
  • Psych Desktop – GPLed webtop with a powerful UNIX-like console
  • Purefect Desktop – Web desktop with a powerful IDE
  • SSOE – Flash-based webtop a lot of features
  • StartForce – Powerful WebOS with tons of apps and features makes the descendant ofOrca Desktop a hit
  • Xindesk – File sync, a powerful API, and much more are included in this great WebOS
  • Webdesk – This Indian webtop includes 1GB of space, POP3 client, PIM, and a nice modules API
  • Webdows – We don’t know how long it will take Microsoft to sue these guys, but it’s a real enjoyment in the meantime. It has XP and Vista styles (including a few Vista effects), FTP, file sharing, IM, and much more
  • Widgets Gadgets – AJAX desktop with tons of apps and a working API
  • YouOS – File sharing, powerful shell, and 700+ applications are all available with this wildly popular operating system
  • ZimDesk – Slick WebOS with tons of apps.

How To Set A Password For Grub At Boot Time in linux

1Grub is the linux default bootloader.
Setting up a password in grub is quite an easy task.you can set the password just at boot time to prevent anyone from logging into the system in any mode.
here is how to do it.
Enter the command line and type

you will be prompted to enter the password..after entering the password twice you will be provided with a encrypted value as shown below..
grub pass
copy this encrypted value.
now open the grub.conf file.
#vi /boot/grub/grub.conf
and enter the line
passwd   –md5    $1$Tqro5/$pkEbG8f4igg0oZRCoWznb1
where the above encrpted value is the one generated at the time when you entered the password.
also enter
at the end of the red hat container as shown in the figure below.
come out of the editor and then reboot.
#init 6
now at startup you will be asked for the password.
press ‘p’ for password.
and enter the password.

Which Linux distribution has ease of use?