Linux people like to claim that directories are really just another type of file. This statement can be misleading. We saw in a previous article that you create a file using a file editor. We will see later in this article how to create a directory.

So just what is a Linux directory? A directory is a collection that may include one or more directories, one or more files, or in fact be empty. You may think of a directory as a computerized file folder or loose-leaf notebook that contains dividers (themselves directories) and pages (files.) Just like a notebook page may not contain a divider, a Linux file may not contain a directory.

Up to now our comments about Linux directories hold for Windows directories as well. Now let’s take a look at some differences between these two systems. First come the naming conventions. Linux always distinguishes between lower-case and upper-case characters in directory names. Microsoft Windows does not. For example, Linux treats pay12june and Pay12june are as two different directories, as different as the directories pay12june and heighho. These directory names were used as file names in the previous article. While Linux does have some reserved directory and file names, in general one cannot tell by the name whether it is a file name or a directory name. So be careful. Linux helps you out here ‘ the ls command that lists the contents of a given directory usually displays files and directories in different colors.

Directories are hierarchical. They resemble a tree or a family tree. But unlike a tree (or Microsoft Windows) Linux has only one root. The root, designated as / lies at the top, rather than at the bottom, of the hierarchy. Right underneath the root directory you will find several subdirectories. For example, the /home directory is a child of / the root directory. The number and names of the first-level subdirectories vary from one version of Linux to another. For example, some Linux distributions include a /root directory while others do not. The /root directory (or subdirectory, both terms are used) is a child of /, the actual root directory.

The /home directory is an important directory. It is divided into subdirectories, one for each user. We like to work with Damn Small Linux, a free version of Linux that runs on the Windows desktop and requires only 50 Megabytes of disk space. Damn Small Linux automatically creates a user called dsl whose home directory is /home/dsl ; a working area essentially reserved for this user. All Linux versions subdivide the /home directory into user subdirectories according to this simple naming convention.

Linux provides several commands to process directories. For example, the mkdir command creates a directory. The rmdir command removes a directory, but in the simplest case only when it is empty. The cd command changes the working directory, the directory in which you are positioned. The pwd (print working directory) command displays (not prints) the working directory. Beginners should run this command often to reduce errors. For example, if you, the dsl user, think that you are positioned in the /home/dsl directory but in fact are positioned in the / directory you won’t be able save your files with a simple command. Why? Because you lack the requisite permission, the subject of our next article.

By: Levi Reiss

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Linux is the most popular operating system so far as security and performance is concerned .It is a Unix-like operating system and is the best example of open source development and free software; generally all underlying Linux source code can be modified, redistributed and used freely by anyone. Red Hat Enterprise Linux 5.2 is the latest version of Linux operating system.

As we all know every operating system has its demerits or failures and can give errors at any time with out any prior information. There are some common error messages faced by Linux users while using this operating system. Some of the most common ones are the following:

• Unknown terminal type Linux.

• Unrecognized option ‘-m486′.

• bdflush not running

• cannot read table of mounted file systems

• Unknown terminal type Linux.

• Cannot initialize drive XYZ?

• EPERM Operation not permitted.

• Unrecognized option ‘-m486′.

• Modprobe can’t locate module, “XXX,” and similar messages.

• Mounting unchecked file system.

• EINTR Interrupted system call.

In most the situations given above a user faces any of the mentioned problems, it becomes difficult for him/her to access or manage his data. He/she won’t be able to do normal tasks which can otherwise be performed effortlessly. If the data which has been rendered inaccessible is important then it becomes essential to recover that data as soon as possible. In this case, he/she would need the help of Linux data recovery software.

Linux Data Recovery Software is an ultimate way out for all Linux related data recovery problems. It also recovers data from formatted hard drives also where file systems have been changed. It recovers lost logical drives and data from physical disk or any removable media.

Stellar Phoenix Linux Recovery software provides data recovery from Ext2, Ext2 and Reiser FS file systems of Linux operating system.

By: allen

Lora Bentley spoke with Amanda McPherson, marketing and developer programs VP at the Linux Foundation. She and two colleagues recently released a new paper, “Estimating the Total Development Cost of a Linux Distribution.”

Bentley: Your study found that it would cost $1.4 billion for a company to build the Linux kernel from scratch today, and $10.8 billion to build an entire Linux distribution similar to Fedora 9. Can you explain how you reached those figures?

McPherson: The conclusions were reached by using David Wheeler’s well-known SLOC tool, SLOCCount, which makes use of the industry standard COnstructive COst MOdel (COCOMO). This methodology takes into account lines of code written, the appropriate number of labor years, and salary adjustments for inflation. We wanted to come up with a real number based on the one thing you can quantify in open source — code. We used a well-regarded methodology and tool that had been used before. Instead of making random projects, we thought this was the best way to approach it.

Bentley: Why the Fedora community distribution and not another?

McPherson: Fedora is the basis for Red Hat Enterprise Linux, which represents a large percentage of the Linux market. This provided us with a very relevant model to assess. Also, David A. Wheeler had used Red Hat for his study in 2002. OpenSuse and Debian/Ubuntu would, of course, also be great targets for this study. We may do that at a later date. We also would like to use an embedded distribution.

Bentley: What do or should these findings mean to proprietary software vendors?

McPherson: I think it means the future of software development is collaborative. These systems have grown so powerful and so important that for any one company to fund the development on its own would be a foolish and possibly financially untenable decision. Software development today actually requires collaboration in order to innovate at the pace the market demands. Consider devices like the Kindle and Gphone. They wouldn’t likely be available today were it not for the billions of dollars worth of R&D that they can use from the Linux kernel. You see companies like Intel using Linux and open source components in the Moblin project to expand the use of netbooks running its products. Intel could instead develop proprietary software in-house to meet this need, but why would they when they can make use of billions of dollars of free R&D? Things have changed since the desktop computer revolution.

Bentley: Don’t many proprietary software vendors recognize the value of open source now given that so many use open source in some way or another?

McPherson: Absolutely! You can also look at our “Who Writes Linux” report to see that hundreds of companies support Linux development directly. This study shows that those companies (such as IBM, Intel, Red Hat, Novell and HP) have made a very smart decision. They can fully participate in a large ecosystem and make use of free R&D without having to shoulder the burden all alone.

Bentley: So why is a study like this one helpful?

McPherson: Sometimes it’s easy to take a ubiquitous piece of technology for granted, especially one you can use for free. I think it’s not just Linux we take for granted: Just imagine the R&D value of the Internet itself and what that means for our economy. Compared to that, Linux seems small, yet when you think about all the innovation it’s powered or is powering, you start to get the idea. I honestly can’t imagine where we would be if Google had had to pay a company a per-server fee for its servers. I do not believe the economics would have been there to build out the powerful search network that we all use everyday. This study makes us appreciate the sometimes-unheralded piece of software and the license that has powered this innovation.

Bentley: Do the findings have added significance in light of the current economic climate?

McPherson: I think so. Linux has always been a lower-cost alternative to Windows, but this report illustrates its economic impact on technology innovation. It’s exciting to see how the collaborative development model is fueling a new category of devices and technologies that would be at least a decade into the future if it weren’t for Linux. Let’s remember that in software, time is money; oftentimes time is more important than money. For a company like Google or Intel to be able to make use of this code that has taken years to develop, drives innovation and keeps costs low for consumers.

By: Lora Bentley