Unix Programming - What is Process?

Post 1

Today, we have so many programming languages and many software that have been created with those programming languages. It is surprising to see that an operating system design is still scaling from mini devices such as watches, washing machines to super computers and clusters. KISS, stands for Keep It Simple and Stupid, an acronymn given any piece of software that does one thing and does it well. It is not overstatement if I say Unix is a cornerstone in computing. There has been so many software that were produced but yet it is difficult to find one something like Unix. Unix is such a marvelous creation like the ones of Bethoven, Michaelanglo. The concept of Unix is simple - Process have life and files have space. Many operating systems have cloned the concept and design philosophies of Unix. If your Unix/Linux system is doing something, it should be combination of Processes and Files. In this post and few (not sure how many) subsequent posts, we will discussing more on Unix/Linux programming concepts  predominantly from user space and from kernel space as and when it is required. My intention is not cover the entire stuff in a single post, but rather I want to be consistent in posting short post. I feel, it is gives a sense of accomplishment to interested readers after reading few posts. It also gives better retaintivity as you can come back to short posts and quickly go through it which improves your short term memory. Without wasting much time, let us get into action.

What is a process? A process is a live entity, it is a program under execution. But when you generalize with such as definition, we tend to forget what really is a process. This may be an answer that you can give in an interview but not when you are trying to understand the system. It is the processes that move the system. Apart from being a program under execution, what is the process? A process is a black box that takes input, processes it and produces the output. It is an algorithm or group of algorithms that is running on the computer. When you say "taking input", what sort of inputs does it take? The input can be a data from a memory location, a stream of bytes from hard disk or network hosts, a signal from its fellow process or its parent and the input resources can be of any form. So, now you know that you need input. The next thing is how do you intend to operate on the input data. Apart from input resources, you also need a logic (code or machine instruction) that processes the data. Until now we have seen data received from input resources and code that processes the data both requiring some space. After you manipulate the data, you need store the data to a output resource or device. But generally, computing is not that simple. Before storing it to output device, you may need to have so many intermediate stages as a part of your algorithm. When you connect these things, you will get the process. A process is not just a program under execution but much more than that. A process is live entity that has address space, context, input resources (open files, database connection, sockets) and output resources (open files, database connection and sockets), state and so many other things in user space and as well as in kernel space. Not only user space, the process has also something in kernel space like per process area and data structures to access the input/output resources. Everything put togother is a process. It is not just code, it is much more than that.

Assume that you have given a billion dollar to answer this question. If you know "C" programming language or if you do not know "C" you can take any programming language. Can you give me a write up (you can to the comments section) on how the following program is executed in a Unix/Linux system. If you answer this question, I believe the size does not matter. You can work on super computers or high performance clusters. Here you go.

int main()

{

    char *str = "Hello, World";

    printf("%s", str);

    return 0;

}

In the next post, we will be discussing how this program is loaded into the memory and how the address space of this process is going to look like and then slowly move on to how this process is executed, how "Hello, World" is printed.

Catch you later.

Emma - Java Code Coverage Made Easy (Part 3)

Before reading this post, I would suggest the readers to go through the previous posts (Part 1and Part 2) for better understanding even though this post alone can be of use but when combined with other previous will help you to understand the whole context of code coverage. In the first post, we understood the importance of code coverage and the second post talked about Emma's on-the-fly instrumentation. Before dealing with other possible ways of using Emma, in this post, I would like to give an overview about Emma. The intention of having previous posts is to help someone to get off the ground and this post will help to understand Emma. This post will be predominantly theoretical (which is very much needed to understand how tools are written for Java in general and how Emma is implemented in particular). With the information given in this post, you will be able to come to decision on how to use Emma effectively.

In the world of Java, you can write tools in whichever way you want. However, Java gives you at least two standard way of writing tools. These are defined as specification. The first method is something to do with "monitoring and managing" runtime behavior. Java Platform Debug Architecture, Java Debug Wire Protocol, Java Virtual Machine Tool Interface and Java Debug Interface primarily do "runtime monitoring and managing". The concept can be put simply put as "watching what JVM does and taking actions based on JVM behavior". The tool should listen what JVM is doing through events and write logic - what the tool intended to do. The main disadvantage of this is approach is the overhead in receiving the events and processing the events.

Another standard way is to add the logic to the class files. Let us consider code coverage. The objective of any code coverage tool is to measure the coverage line by line. In order to do this, the coverage tool injects the code coverage logic in all class files. Whenever the class is loaded and executed, along with the application logic, the code coverage logic also runs and records the coverage metrics. This is called as bytecode instrumentation. Again, there are two ways of doing this. First is to modify the application class in the hard disk (or any secondary storage) and the second method is add the bytecode on-the-fly when the classes are loaded.

Emma exploits both the methods and hence it lets users to measure the code coverage both offline instrumentation and on-the-fly instrumentation. The caveat is that during the on-the-fly and offline, the way the application is measured for coverage is not going to vary. Only the method used to inject or instrument bytecodes is going to vary (which we described already).

Emma employs on-the-fly instrumentation if you have integrated Emma with IDEs. The command line version of Emma has the capability to run both in offline and on-the-fly instrumentation mode. Most of the times, the developers/testers use on-the-fly instrumentation since the risk of changing the application classes is not there as bytecode instrumentation happens on-the-fly. But the life is not easy as it seems. When you are using certain application servers or servlet container, you cannot use on-the-fly because the application servers/servlet containers have custom classloaders. Here offline instrumentation is the only option. So, before using Emma, you may need to study little bit about your application and use the suitable methods.

I have also come up with a little interactive presentation with flash using Wink on Emma. It can be accessed through this link

Hotswap Agent for Java Virtual Machine (Part 2)

This is the second post in the series of posts on writing Hotswap agent for Java Virtual Machine. In the previous post, we saw an higher level overview about the requirements and specification on how it can be done. In this post, we will drill down to the details. I am also planning to write few more posts on implementing this agent using Java Debug Interface. Also, once you understand this Hotswap agent, you can write a lot of tools using Java Debug Interface. The rest of the post gives the details of how to write an agent using JDI.

Java Debug Interface is a programming interface which lets us to write agents that interact with a live JVM. The interaction is of two types. First, JDI gives infrastructure to receive events from the JVM. For example, whenever an exception is thrown, JVM publishes an event. With the help of JDI an in-process agent or an agent running as different process in the same or different system can consume the event. Secondly, with the help of infrastruture given by JDI, the agent can also control JVM. The events together with controlling of JVM helps developers to write tools such as debuggers and profilers.

When you are going to write an agent (a program that monitors and managers remote JVM) using JDI, the first thing that you have to do is to know how are you going to connect to JVM. There are mutiple connectors available. Each connector differ in the way on how they interact with the JVM. For example, LaunchingConnector helps you to launch a JVM before connecting to it but ListeningConnector simply listens to a running JVM. Next thing is the transport mechanism, the method of communication between JVM and the agent.

After deciding both of these, you need connect to JVM. If the connection is successful, you will get an instance of JVM. With the remote JVM object, you can subscribe for specific event by through JDI request. Apart from this, using classes and methods in JDI, the agent can also control JVM such as stopping a thread, running garbage collection, redefine and reload classes etc. The following is the list of events that an agent can subscribe for.

AccessWatchpointEvent
BreakpointEvent
ClassPrepareEvent
ClassUnloadEvent
Event
EventIterator
EventQueue
EventSet
ExceptionEvent
LocatableEvent
MethodEntryEvent
MethodExitEvent
ModificationWatchpointEvent
StepEvent
ThreadDeathEvent
ThreadStartEvent
VMDeathEvent
VMDisconnectEvent
VMStartEvent
WatchpointEvent

If you want to write a simple tool to reload classes on the fly, you have to identify Connector, Transport, subscribe for events like JVM Start, JVM End. You have to use redefineClasses method and then reload the classes into the JVM. I believe, this post would have given you some idea on how to write a Hotswap agent. In the next post, we will see the implementation of Hotswap agent with the help of code.

Emma - Java Code Coverage Made Easy (Part 2)

This is the second post on Java code coverage with Emma. In previous post, we discussed about Code Coverage and introduction to Emma. In this post, we will discuss about how to install Emma and do the basic code coverage with an example and screenshots. After you complete the reading of this post and previous post, you should be able to download Emma, install it and run Emma from command line. Towards the end, we will also discuss about how to get HTML report and interpret simple Emma report. It will be good if you can download Emma from here and use it side by side as you read this post. Please make sure that you download the binary of Emma and not the source version. The binary version of Emma should be sufficient to do this. Along with this, you need to have Java compiler and Java Runtime Environment to compile your Java classes. In order to give a picture of how Emma works and process involved, let us take the toughest approach of running Emma from command line rather than integrating with IDE. In later posts, we will discuss about IDE integration (Eclipse/Netbeans) to make developers life easier.

Downloading and Installing Emma
Emma comes in three different versions - binaries with examples, source and libraries. In order to do this example, we need to download "binaries with examples and documentation". You can directly download it form Sourceforge.net or you can access Sourceforge project via Emma home page. Irrespective of the way you choose, please make sure that you download Emma binaries with example version. After downloading emma..zip, unzip in a directory. You find three directories "docs", "examples" and "libs". Inside the directory "lib", you will find two JAR files emma.jar and emma_ant.jar. For time being, we will not be requiring emma_ant.jar as it is used to integrate with "ant" which we will cover in subsequent posts. The JAR "emma.jar" is the tool that we will be using throughout this example. Apart from the examples given in this post, you can also try to play with the examples that comes with Emma. Take "emma.jar" from the extracted directory and copy it to the directory where we have our examples. The following picture shows my setup.

Emma.jar and Examples

Java Program Example
Consider the following Java classes. Greater.java is the main class that we are going to test and measure coverage with the help of GreaterTestDriver.java. The class "GreaterTestDriver.java" mimics the testing of the class "Greater.java".

GreaterTestDriver.java

Greater.java

Greater.java has compare method and it prints out the largest of two numbers. GreaterTestDriver.java creates an object of "Greater.java" and invokes compare method passing values 10 and 5 respectively. For values 10 and 5, if block in the method compare is executed and else part will not be executed which our coverage has to pin point.

Running Emma
Running Emma is simple and you only need to specify emma.jar in the classpath and run your application using "emmarun" command. In our case, it is running the test driver "GreaterTestDriver" class. Once you run Emma and after you application exits, Emma prints the coverage results in a text file "converage.txt".

Running Emma and Getting output in text file

If you look at the report "coverage.txt", it gives the coverage data at package, block, method, class and line level.

You can also run Emma and get report in HTML format. Again it is very simple and you need to specify that in command line options (refer the last boxitem to know more about command line options used in this post).

Emma with HTML Reporting

So far you have run Emma and got the HTML report. But the data given by Emma shows the coverage results but the information is not sufficient. It will be helpful to merge the results with source code. Emma can also pin point which lines are executed and which lines are not executed. Yet again, the step is simple and following example is self explanatory.

Emma Reporting with Source Code

In the above report, the lines that are highlighted in green color are the ones that are tested at least once and the lines that are in pink color are not tested. In ideal case, you need to improve your test suite to cover the lines that are highlighted in pink color. As an exercise, can you achieve 100% coverage in Greater.java?

Command options used in this example

# In order to run Emma from command line and to get report in test file

java -cp emma.jar emmarun -cp . example.GreaterTestDriver

# In order to run Emma from command line and get report in HTML but without Source Code

java -cp emma.jar emmarun -r html -cp . example.GreaterTestDriver

# In order to run Emma from command line, get report in HTML and merge the result with Source Code

java -cp emma.jar emmarun -sp . -r html -cp . example.GreaterTestDrive

In this post we saw only on-the-fly instrumentation and in upcoming posts we will discuss other features of Emma such as Eclipse (and Netbeans) integration, off-line instrumentation, integrating with ant and merging data of multiple sessions, integrating with Tomcat.

I have also come up with a little interactive presentation with flash using Wink on Emma. It can be accessed through this link

Hotswap Agent for Java Virtual Machine (Part 1)

Before joining my company and in fact until two years after I joined my company, C, 8085/8086 ALP and Perl are the programming languages I knew. I learned C and ALP at college and Perl at my office to write a simple CGI utility. Two years later, I started to learn Java as I was moved to development team and I started to learn Java with certain amount of dislike. After a short period of time, I started to read about Java Virtual Machine specification and writing tools with the help of JPDA. Writing tools using JDI/JPDA is relatively simple as JPDA gives you enough infrastructure. This post contains specification/requirements for writing a small and powerful agent to reload classes of live JVM. As you may know, Java source code is compiled and bytecodes are produced. These bytecodes (generally .class files) are loaded into JVM and are much like machine instruction but the fact is that only JVM can understand it. These bytecodes are your program and decides how your application is executed.

If you are a developer, your daily job might be writing code or fixing bugs or both. During development, you may need to change the logic of your program, recompile the source and restart the application. Restarting the application is stopping the running JVM and starting a new JVM process. This is a very lengthly process if your work involves changes to source code multiple times. Sun HotSpot VM comes with a feature called HotSwap. Using this feature one can replace the classes that are loaded in the JVM. Once reloaded, the objects that are already created also takes effect with new changes. This tool will improve the productivity of developers when frequent restart of the applications is required. Here is the specification.

Specification

Write a simple tool which let you to reload classes in a running JVM without restarting your application. Also provide a simple user interface (probably using SWING).

Steps

1. Use Java Debug Interface API to connect to remote JVM. In order to connect to remote JVM, you the hostname/ip address of the remote box and port number on which your JVM runs. In order to hotswap the classes, you need start JVM in debug mode and if you start JVM using "socket" debugger.

2. Also subscribe for few important events such as JVM Exit, Disconnect Event. (for more info refer Java Debug Interface API Spec).

3. If the connection is successful, you get an instance of the remote JVM and you can once again use JDI to replace classes.

4. You have to write the logic of reading the class file (flat file) from the file system and give to JDI. JDI pumps the class file to remote JVM which reloads the class after making lot of checks.

In next couple of days, I m planning to write a post on how to do this with a small example (thanks to Veeru for pointing this out).

Emma - Java Code Coverage Made Easy (Part 1)

Irrespective of the number of lines of code you write and if you are a good (and honest) tester or developer, you accept the fact that it is impossible to test the entire software. I am not talking about those simple programs like printing "Hello, World". I am talking about software that is decent in size. Testing software is brain intensive. I would like to give you a simple scenario how I used to think when I was in testing team (of course, that was 6 years back when I was fresher). When I was executing a test case or writing a test case, I generally used to get few parallel thoughts about what are the other related test cases. It never ceases there. It went on and on until I felt comfortable. If I did not cover some corner cases, something would pinch me from inside to do more, to spawn many parallel thoughts and eventually I would end up writing more test cases. While this approach is good, but this is very subjective and depends on the person who is testing. It depends on the knowledge level and expertise of the person who is doing the testing. The testing should be much more and also driven by data. Even if we take that most of the testers of are effective, how are we going to convince and be sure that the test cases are effective?

As a tester, we generally used to get requirements, design documents (?) and finally code in binary format. If you apply general system thinking, tester is above developer simply because he supervises developers' work and validates it. The confidence level of the tester has to impeccable so that the project managers, product managers can have sound sleep and sound sleep every night. This confidence comes with thoroughness of testing and this ability is only possible if you eat, sleep, think with testing in your head and practice testing as art. You might be watching YouTube, but yet you will think like a tester. You might be doing test strategy, test planning, test plan, sophisticated test case design. All these comes in the following ways - requirements, design document, your understanding about how the code will look like and ad hoc testing. But is that sufficient. We are living in the world of doing more and wanting more, testing effectiveness is no exception. Is there a mechanism by which I can measure my test suite effectiveness. Yes, it is there. The rest of the post deals with doing code coverage for Java applications using Emma, an open source code coverage tool.

First, what is code coverage? The process of measuring or seeing which part of code that are tested and the areas that are not at all tested is called code coverage. Second, why is it important? The answer is read the definition again. Period. If you are unit testing you code, it helps you to see the coverage immediately and hence you can fix it "then and there" and butterflies will not fly in your stomach when the product goes to testing team. If you are a tester, it helps you to measure - first your test plan and then the code. Naturally, you will write more test cases or change the existing test cases to cover more. The point is "more coverage". So, no more butterflies in your stomach too when your product goes out to production.

Emma is an open source software which is simple, powerful and flexible. Emma uses bytecode instrumentation technique and measures the code coverage. It has the ability to instrument the classes on-the-fly and also supports offline instrumentation. In on-the-fly instrumentation, you just give the location of your Jar file or class files, Java Virtual Machine when it loads the classes it instruments the logic for code coverage. In offline mode, you need to do an additional step of adding the logic to Jar/class files and copy it in your hard disk and load the instrumented classes to Java Virtual Machine. But irrespective the method you choose, the code coverage will be same. The offline mode is particularly helpful when you have custom classloaders like application servers or servlet container.

You can run Emma directly from command line and you can also integrate with nightly build as a part of continous improvement strategy. Ideally, in nightly build, code coverage works hand in hand with Unit Testing Framework like JUnit. After instrumentation, you have carry out your testing. When you are testing, Emma does the code coverage. Once you are done with the testing, you can safely stop the application. Emma also comes with reporting and it can produce reports in HTML and XML. The report can also be merged along with source code and by just looking at this report, you can identify the lines that not covered.

Apart from running Emma from command line and including with ant, it can also be used at developer's desktop. Emma has plugins for famous IDEs - Eclipse and Netbeans. With this, the developer's can run their unit test cases with Emma immediately after implementing a unit of code. Based on the coverage, they can work on their unit test cases to achieve better coverage. Better coverage, better quality and improved confidence. With this, we come to an end on introducing Emma - Open Source Java Code Coverage Solution.

In the next post, we will be discussing how to install Emma and use it.

Have a Great Day

I have also come up with a little interactive presentation with flash using Wink on Emma. It can be accessed through this link

Speaking Experience @ ILUG Chennai Monthly Meet

This is the first time that I am speaking in Indian Linux User Group, Chennai. ILUG is most active LUGs in India. The meeting generally happens in IIT Madras (the place I wanted to study). Again, I want to reiterate the fact that speaking about Open Source in Open Source meeting gives me enough motivation and abundance of energy. I registered the topics with Mr. Bharathi Subramainan and he gave be slot immediately. Today, I also noticed what happens when people with passion sign up to do something. Unlike other meetings, the members were very punctual and I could see considerable number of people waiting in the hall and some people working in computers in another room. Today's incident enlightened me about valuing others time and I will never forget this in my life. Apart from that we also had good knowledge sharing session.

The talks started at 3.15pm and the first talk was hosted by Selvakumar K from NRC-FOSS on KTechLab, an Open Source IDE for Electronics and PIC Micro Controller Circuit Design and Simulation. He talked about analog and digital simulation tools in Linux. I feel that the tool will help any electronics student to do experiment in his/her laptop/computer. The colleges should seriously consider to have this tool in their department and encourage students to use when they are doing practicals or learning theory.

Next, I started my talk on Java Code coverage and explained about need for code coverage and features of Emma. I talked about various ways of using Emma such as with IDE, nightly build, from command line, online instrumentation and off-line instrumentation. Towards the end, I gave a quick demo on using Emma with Eclipse, on-the-fly instrumentation from command and HTML reporting.

Towards the end, Prof Dr C N Krishnan talked about NRC-FOSS and its Phase 2 initiatives. He requested the help from ILUG-Chennai. He also expressed his concerns on giving feedback to NRC-FOSS.

We have also been given some stickers, pens and Fedora CDs sponsored by Ubuntu and the speakers have been given caps (so, I got one) from Ubuntu. This Saturday was fulfilling and exciting as well. Looking forward for more such knowledge sharing session.

Creating Virtual Machine in VirtualBox - Screenshots

For more than four years, I have been using VMWare workstation and from last year I started to use Virtual Box. Virtual Box is a virtualization product by Sun which virtualize X86 platform and supports Windows, Linux, Solaris and Open Solaris as guest operation system. It is good that Virtual Box is released under open source license and it is available for free of cost. You can download Virtual Box from here. Installing Virtual Box should not take more time and it is very simple like installing any software. Just double click the binary executable and answer few usual questions. You are done. I captured the screenshots of creation of Ubuntu Virtual Machine. One feature, I like about Virtual Box is you can reuse Virtual Disk. We will see this in another post. I am presenting the screenshots that I captured. By following this post, you should be able to create a virtual machine and start installing operating system of your choice.

1. Create New Virtual Machine

2. Click Next in "New VM Wizard"

3. Specify Operating system, distribution and give a name to this VM

4. Specify the virtual RAM size (leave at default)

5. Create a new VM and new virtual disk

6. Click next in "Virtual Disk" Wizard. This is the sub-wizard in the main wizard. If you already created virtual disk, you can skip this setup by choosing virtual disk from available list.

7. Choose virtual disk storage type (leave at default)

8. Specify a name for Virtual Disk and size

9. Click "Finish" to create virtual disk

10. Click "Finish" to create VM. After this step, a new VM should have been created.

11. Open settings and choose either CDROM or ISO file location. So that VM will use CD/ISO for OS installation

12. And finally start the VM. Now VM is ready to install Operating system. From here, VM is as good as physical machine.

In this post, we saw how to create virtual machine. The steps are same irrespective the guest operating system. Virtual Machine behaves much like a physical X86 based system and as of now many flavors are Linux, Windows, BSDs can be installed as guest operating system. Guest operating is the operating system that gets installed in the virtual machine. For example, in a Windows XP system, we can virtualize many virtual machines. The operating that gets installed in the virtual machine is generally called as guest operating system.

Creating a WoW

We, as a human being are like goats. By and large, we go with majority. When so many people in a room say that "world revolves around me", we will also agree with it. If they say, they want to create a wow, all of a sudden and without understanding the science and art of innovation, we will jump in and say "yes, we will". Up to this, it is quite good. At least you have the curiosity. But the worst things is many of us tend to stay in the same place without taking any initiative. We just want to build a marvelous building at this moment without any foundations/hard work. Creating a wow or innovation is easy. But it is not so easy and does not come just like that. I am not a innovator and I have distantly worked with some innovators. Here is my point of view.

Many of us are working on creating wow for others. I don't question the willingness and focus to create wow for the others (mainly customers). But I do like to ask you a question. Have anyone did something for you that impressed you. Otherwise, did anyone in your life created a wow for you. How does a wow smells, what do you feel about it, does it speak to you? When someone did it, did you feel that you were in heaven. Without understanding what a wow is and without even experiencing something, how can you create a wow. Even if you create a wow, how can you say that it is "wow". Creating a wow once or twice is easy and may be gotten due to luck. Do you know how to do it consistently? Do you have the magic of converting the air as wonderful music like a flute.

First of all, may it be innovation or quality or productivity, it sucks without daily improvements. The daily improvements are the foundation. Here my point is not the final product (the big idea) but it is what we do to bring that big idea. The knowledge we gather, the type of people we interact, the number of minutes, hours we think and so on. Without focusing these foundations, creating a wow is just a lip service and I am sure that it is never going to happen. Innovation is a chemical reaction, the reaction that takes place in your brain and you really need to work hard and be consistent in fusing your neural circuit.

Creating wow is not an one time event. We need to come up with techniques where we can create wows like an engine. The customer may not like to stop with just one idea. She wants two, three, and infinite. The ideas are going to give an impression , and it is also true, that you care for her (though it is not the only way to impress). So, if you are consistent, you will be in the game. Else the customer is going to say that you are outdated.

Another thing that we are doing is "ritualize" wow creation rather than internalizing it. When you practice as a ritual, you do it but without involvement, passion and halfheartedly. After internalizing and comprehending it, you do it more with involvement and wholeheartedly. This is another key thing that we need to watch out for.

The final thing is give people the resources and freedom. The resources can be in terms of time and environment that is suitable for creating wow. You cannot expect an idea when people are squeeched and used to maximum possible extent. If you ask a stressed guy, he can only give mediocre ideas. Give them time to think and then expect sparkling ideas.

The above discussed things are my viewpoint. I look forward for your response/comments to learn more on this.

Economic Slowdown - When are going to hit the ground?

It is a trillion dollar question that when are we going to hit the bottom before making a recovery. This is a very hot news and it is minutes after US Fed released minutes. In summary, Fed sees that the economy is deteriorating and downside risk is high. And another point here is the economy is deteriorating more than expected and it is likely that the customers will hold back the spending which again lead to production cuts which leads to lay-offs. This is going to be cyclic and will take sometime to break the cycle and to go in counter direction. In summary, there is lot of downside risk in short term before something happens in a long term

Hold your breath and read through these pages.

Google News
Yahoo News
CNN
Bloomberg

Again, in another two months, the markets are going to see another bottom, may it be capital markets or job market. Now, we should believe someone who says the recovery is going to take three years :-(. Hard truth, but it is truth, we have to digest and move forward.

How to Mount Windows Partition from Linux

I have dual boot in my laptop with Windows XP and my favorite Ubuntu. Windows XP is factory default. Two years back, I installed Fedora and after trying the recent version of Ubuntu, I wanted to install Ubuntu and it has become my favorite in no time. I simply like it. Since I backed up some important Ebooks and documents into Windows partition, I wanted to access those both from Windows XP and Ubuntu. After doing some searching in Internet, I found a mechanism to mount windows partition to Linux.

First, you need to identify the number of Windows partition and locate the partition that you want to mount. "df -k" will help you to identify all the partition/disk in your system. Then, use the "mount" command to mount. For example, here is the sequence of steps to be followed. Run "sudo fdisk -l" and identify windows partition and then mount it using script given after fdisk output.

lnarasim@lnarasim-laptop:~/scripts$ sudo fdisk -l

Disk /dev/sda: 78.5 GB, 78518522880 bytes
255 heads, 63 sectors/track, 9546 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xd0f4738c

Device Boot Start End Blocks Id System
/dev/sda1 * 1 1958 15727603+ 7 HPFS/NTFS
/dev/sda2 1959 9546 60950610 f W95 Ext'd (LBA)
/dev/sda5 1959 4569 20972826 7 HPFS/NTFS
/dev/sda6 4570 4736 1341396 7 HPFS/NTFS
/dev/sda7 4737 4985 2000061 82 Linux swap / Solaris
/dev/sda8 4986 9546 36636201 83 Linux
lnarasim@lnarasim-laptop:~/scripts$

lnarasim@lnarasim-laptop:~/scripts$ cat win_mount.bash
#! /bin/bash

sudo mkdir -p /media/c
sudo mkdir -p /media/d

sudo mount -t ntfs -o nls=utf8,umask=0222 /dev/sda5 /media/c
sudo mount -t ntfs -o nls=utf8,umask=0222 /dev/sda6 /media/d

I have also come up with a simple shell script to do that. If you want, you can also add this in startup scripts so that Windows partition is mounted automatically after startup. With simple use of Linux commands, we are able to access Windows partition.