Linux source code is available to

Operating System — Linux

Linux is one of popular version of UNIX operating System. It is open source as its source code is freely available. It is free to use. Linux was designed considering UNIX compatibility. Its functionality list is quite similar to that of UNIX.

Components of Linux System

Linux Operating System has primarily three components

Kernel − Kernel is the core part of Linux. It is responsible for all major activities of this operating system. It consists of various modules and it interacts directly with the underlying hardware. Kernel provides the required abstraction to hide low level hardware details to system or application programs.

System Library − System libraries are special functions or programs using which application programs or system utilities accesses Kernel’s features. These libraries implement most of the functionalities of the operating system and do not requires kernel module’s code access rights.

System Utility − System Utility programs are responsible to do specialized, individual level tasks.

Kernel Mode vs User Mode

Kernel component code executes in a special privileged mode called kernel mode with full access to all resources of the computer. This code represents a single process, executes in single address space and do not require any context switch and hence is very efficient and fast. Kernel runs each processes and provides system services to processes, provides protected access to hardware to processes.

Support code which is not required to run in kernel mode is in System Library. User programs and other system programs works in User Mode which has no access to system hardware and kernel code. User programs/ utilities use System libraries to access Kernel functions to get system’s low level tasks.

Basic Features

Following are some of the important features of Linux Operating System.

Portable − Portability means software can works on different types of hardware in same way. Linux kernel and application programs supports their installation on any kind of hardware platform.

Open Source − Linux source code is freely available and it is community based development project. Multiple teams work in collaboration to enhance the capability of Linux operating system and it is continuously evolving.

Multi-User − Linux is a multiuser system means multiple users can access system resources like memory/ ram/ application programs at same time.

Multiprogramming − Linux is a multiprogramming system means multiple applications can run at same time.

Hierarchical File System − Linux provides a standard file structure in which system files/ user files are arranged.

Shell − Linux provides a special interpreter program which can be used to execute commands of the operating system. It can be used to do various types of operations, call application programs. etc.

Security − Linux provides user security using authentication features like password protection/ controlled access to specific files/ encryption of data.

Architecture

The following illustration shows the architecture of a Linux system −

The architecture of a Linux System consists of the following layers −

Hardware layer − Hardware consists of all peripheral devices (RAM/ HDD/ CPU etc).

Kernel − It is the core component of Operating System, interacts directly with hardware, provides low level services to upper layer components.

Shell − An interface to kernel, hiding complexity of kernel’s functions from users. The shell takes commands from the user and executes kernel’s functions.

Utilities − Utility programs that provide the user most of the functionalities of an operating systems.

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Linux source code is available to

Advantages

1. Open Source
2. Freedom to modify
3. Low resource requirements
4. The best security
5. Virtually immune to viruses
6. Exceptional stability
7. The best technical support
8. Bugs are fixed quickly
9. No vendor lock-in
10. Extensive hardware support
11. Many free tools and applications
12. Ultimate product continuity
13. Broad interoperability
14. Strong remote access
15. Low Total Cost of Ownership

Disadvantages

1. Fewer business applications
2. Incompatible distributions
3. Knowledgeable administators required

Other issues

1. User interface
2. Migration
3. No one company is responsible

What is Linux?

GNU/Linux is an operating system that has, among other things, become an alternative to Microsoft Windows. It’s a free or very low-cost Unix-like system that has a reputation for being secure, efficient and extremely stable. The Linux kernel was first developed in 1991 by Linus Torvalds while he was studying computer technology at the University of Helsinki. The operating system was completed when Torvalds and other team members combined the Linux kernel with system components developed by members of the Free Software Foundation for the GNU Project. It is therefore often referred to as GNU/Linux, which is a more accurate description of the complete system.

Tux, the Linux mascot (Torvald’s Unix).

GNU/Linux is a remarkably complete operating system that includes a huge collection of tools, an X Window System graphical user interface, many major applications, as well as support for just about any networking protocol and file system you can think of. Versions of Linux are available for virtually every hardware platform available, from PDAs (such as the PalmPilot) to PCs to supercomputers.

Unlike Windows and other proprietary operating systems, GNU/Linux source code is completely open to the public (Open Source); everyone is invited to modify and build upon it, i.e. contribute. Although copyrights are held by the individuals who developed the system’s components, Linux is distributed under the Free Software Foundation’s copyleft stipulations. Copyleft entails that, if any such code is used or modified to produce new applications that are redistributed, that source code must also be free.

From a business point of view, if you’re currently using Microsoft Windows systems for everything, you will probably want to use Linux for one or more of the following reasons:

It dramatically decreases IT costs.
Using Linux can, for instance, reduce the cost of software by anything up to 100%. It also allows organizations to avoid upgrading their hardware every time they need to upgrade their software.

It dramatically increases IT quality.
Using Linux can, for example, lower maintenance and administration costs. It always increases efficiency and availability.

It’s a system you can trust.
Linux is guaranteed not to come with any backdoors, tracking systems or similar security risks.

For a more complete set of reasons to use Linux, we’ve compiled the following overview of the advantages and disadvantages of moving to and using this alternative operating system:

Advantages of using Linux:

Open Source. Linux source code is freely distributed. This allows many programmers to collaborate on software projects of all sizes in order to offset the cost of development. Quite often, the source code has been reviewed by literally thousands of programmers, vastly improving it. No other operating system has ever been subjected to this level of review. This is a huge advantage, especially when projects are large and complex. The concept of Open Source is directly responsible for many of the advantages that follow.

Freedom to modify. Open Source code is free not only for all to view, but also to modify. Because of this, it is not only possible for it to be made to suit the needs of the many, but also for it to be tailored to suit the needs of the few. Open Source software allows companies to align their IT strategy to their own business objectives, instead of to those of their software provider.

Low resource requirements. Thanks to the contributions of so many, Linux has become a very efficient operating system. In other words, it requires far fewer resources to achieve results comparable to those of Windows. That’s not to say that Linux developers haven’t been working to take advantage of the amazing speed and capacity that the latest computers have to offer. It’s just that there are also Linux solutions available for those who would like to squeeze a few more miles out of their old hardware.

The best security. The principles of Open Source have added greatly to the security of Linux systems. For those with a basic understanding of the rules involved, it’s easy to produce systems that are almost impossible to breach. From an administrative point of view, this makes Linux computers very easy to manage: users can be allowed to do what they need to do, but cannot get themselves into trouble.
As a case in point, it’s an open secret in the defense and intelligence communities around the world that Open Source is the preferred software for secure systems. Due to concerns over bugs, «spyware,» and other security hazards, these people are naturally distrustful of software that they can’t study and compile themselves. Therefore, they would rather use Open Source software for all of their sensitive and classified systems. (Ref: News.com)

Virtually immune to viruses. As a result of its excellent security, Linux systems are as good as immune to virus attacks. Generally, anti-virus software is not considered necessary. This doesn’t mean that Linux viruses don’t exist − of course they do. But, because of the way Linux file system security works, it’s much harder for any virus or worm to infect the system. The only way for this to happen is for an administrator to install an infected program while logged in as the all-powerful root user. However, this need never happen if a system is maintained with caution and common sense.

Exceptional stability. Once again, thanks to Open Source and the burning desire of thousands contributers to create a stable computing platform, Linux has become a rock solid operating system. When configured properly, a Linux system will generally run until its hardware fails or it is shut down; up-times of more than a year are not uncommon. One of the main reasons for this is that, unlike Windows, applications that misbehave or fail have little or no influence on the stability of the operating system.
As an example, in 1999 ZDnet published an article about a 10-month reliability test to compare Caldera Systems OpenLinux, Red Hat Linux, and Microsoft’s Windows NT Server 4.0 with Service Pack 3. All three used identical hardware, and network requests were sent to each server in parallel for standard Internet, file, and print services. The result was that Windows NT crashed an average of once every six weeks, each time taking about 30 minutes to fix; not bad, until you consider that neither of the Linux servers ever went down. (Ref: ZDnet)

The best technical support. Linux is supported by commercial distributors, consultants, and by a very large and active community of users and developers. In 1997, the Linux community was awarded InfoWorld’s Product of the Year Award for Best Technical Support over all commercial software vendors.

Bugs are fixed quickly. Programmers all over the world collaborate constantly to make Linux a better and more stable system. When bugs are reported, nobody tries to explain them away or tell you to wait a few months for a fix. Instead, with so many developers involved, bugs are fixed quickly − sometimes within a matter of hours. Often, those who report the bugs will end up corresponding with the people who actually write the programs!

No vendor lock-in. Since there are no secrets in the world of Open Source, there are no operating systems or applications that customers can get locked into. This gives customers a stronger bargaining position when shopping for new IT solutions. The availability of the source code also means that every user and support provider is empowered to get to the root of technical problems quickly and effectively − even making changes if necessary. This contrasts sharply with closed source, proprietary operating systems, where even top-tier support providers must rely on the OS vendor for technical information and bug fixes.

Extensive hardware support. First of all, Linux has support for many different computing platforms. Standard PC hardware is the most commonly used, but there is also support for a wide range of other computing platforms, including Alpha, Power PC, 680×0, SPARC and Strong Arm processors, and system sizes ranging from PDAs (such as the PalmPilot) to supercomputers made up of clusters of systems (Beowulf clusters). Second, Linux has support for a very long list of peripheral hardware components, such as keyboards, mice, video cards, printers, sound cards, scanners, digital cameras, SCSI cards, and tape devices. Where older hardware is concerned, you’ll often find that Windows has dropped its support while Linux has not.

Many free tools and applications. Most Linux distributions come with a wide range of additional Open Source applications. These include the market leading Apache web server and the powerful GIMP graphics editor. Not to mention a huge collection of tools for system administration and development. On top of that, many commercial applications are also available for Linux.

Ultimate product continuity. Every years, products that many companies depend on are discontinued, or the businesses that produce and support them go bust. This means that, whether they like it or not, the companies that rely on those products will end up paying for expensive migrations to alternative products. With Linux and other Open Source solutions, that need never happen. Since the source code is open to everyone, any organization can elect to maintain the source code for as long as they want, even if nobody else wants to.

Broad interoperability. Linux works together with many different computer systems. It can communicate using the native networking protocols for Unix, Microsoft Windows, IBM OS/2, Novell NetWare, and Macintosh, and can also read and write the disks and partitions used by these and many other operating systems.

Strong remote access. Remote access is a great way to saving money on maintenance and support. Like its relatives in the Unix world, Linux was designed from the ground up with remote access in mind. Using the standard tools available to all, remote access on Linux platforms is fast and efficient, reliable and completely secure − even via the Internet.

Low Total Cost of Ownership (TCO). Due to all of the advantages listed above, together with the fact that Linux and all other Open Source solutions know no licensing costs, the TCO for Linux-based systems is as low as you can get. Productivity can remain high, investments low and expenditures for maintenance and support can be kept to a minimum. To many, this is welcome news in our difficult economic times and it is why a growing number of organizations and governments are using Linux wherever they can.

Disadvantages of using Linux:

1. Fewer business applications. Although most Linux distributions come with an impressive array of tools and applications, there still aren’t nearly as many specialised business applications available for Linux as there are for Windows. This is undoubtedly one of the most important hurdles that will have to be cleared by the Linux community before Linux can become a common desktop solution.

   Incompatible distributions. One of the main headaches for developers, but also for users, is that not all Linux distributions are the same: an application developed for one distribution may not work on another. Sometimes, an application may not even work on a different version of the same distribution. Luckily, the major distributions include all of the most important applications; it’s the more obscure applications that are more likely to be a problem.

2. Knowledgeable administators required. As opposed to the latest generation of Windows administrators, who are generally little more than normal users capable of creating and deleting accounts, an effective Linux administrator has to know a lot more. Such knowledgeable individuals are not as easy to come by, but luckily, once found and employed, they tend to represent much better value for money.

Other Linux issues:

1. User interface. It is often said that Linux is quite different from Windows and that for those wanting to make the switch, the learning curve is steep. Well, Linux is different, so there is an element of truth in this statement, but how much this affects you really depends on where you stand as a user. Here are three different scenarios:
   For home users. As an operating system for the average home user, Linux isn’t the easiest system to set up and expand. The installation process isn’t as automated as that of Windows, and for those who run into problems, the only way to fix things is from the command line. There, knowledge of all kinds of arcane instructions is required. This is okay for dedicated hobbists, but it’s usually too much for the casual user.

   For administrators. The learning curve is the steepest for support personnel that have previously only had experience with Windows. There are many differences to get used to, new concepts to absorb and old habits to unlearn; it can seem like a mountain to climb. However, for those who persist, the rewards are great: levels of control far beyond what they’ve been used to.

2. For business users. With a well-managed Linux desktop machine, the average business user shouldn’t have anything to worry about. They have the best deal because they get all the good stuff, such as the rich graphical user environments now available, but don’t have to worry about about any of the hard stuff; the administrators take care of that. Maintenance, installations, upgrades, troubleshooting and support can all be accomplished through remote access. On-site intervention is only necessary when hardware problems occur.
3. Migration. Any business that considers making a switch from one data management system to another, which is referred to as migration, must consider the cost thereof. Generally speaking, it can be said that the greater the dissimilarities are between the new and the old systems, the greater the cost of migration will be. This is just as true when migrating to Linux as it would be when migrating to any other system. And since Linux is not Windows, there are a few extra things to consider. For instance, a migration to Linux can include, but is not limited to:
   Conversion of data, such as mail files, databases, documents and spreadsheets, to a new format may not always be that easy. With database migrations in particular, it is quite common for at least some data to be lost due to differences in database structure. Remember also that vendors of proprietary software are very good at making it difficult for their customers to export their data to other systems.

   Training of personnel. The average user will probably require some training to use the new applications, although probably not much more than for any new application introduced previously. The support staff, on the other hand, will need considerably more training to be brought up to speed, especially if they have no previous experience with Linux.

4. Developing new policies. Many larger organizations have developed policies for maintaing their software that is based on their experience with commercial products. As things are quite different in the world of Linux, many of these policies will have to be reconsidered.
5. No one company is responsible. This is true: if something about a Linux system doesn’t work properly, there is no particular company that anyone can complain to or ask for technical support. On the other hand, this is typically the kind of argument that is brought forward by commercial software companies. For instance, there are all kinds of drawbacks when only one company is responsible for a software package: support can still be a nightmare, bug fixes usually take longer, and upgrades are often too expensive. And on top of that, companies like Microsoft do everything they can to escape responsibility when bugs are found in their software (just read one of their license agreements).
   With Linux, things are certainly done differently. Users must turn to documentation and user communities for support, reporting the bugs to package managers and developers. However, if most everybody’s questions and bug reports are usually addressed within days instead of months, there’s no reason to complain. In addition, some large companies, such as Dell, HP and IBM, are now guaranteeing the same service-level agreements for Linux that they do for proprietary operating systems.

Last modified: 2017-08-02, 17:31

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