Features of Linux
The Linux operating system provides various features, such as multitasking, shared libraries, POSIX
compliance and virtual memory. Some of these features are as follows:
Î Multiprogramming - Allows programs to be executed simultaneously using the same set of
computing resource. In Linux, multiprogramming is made possible by using the concept of timesharing.
The operating system has to manage various programs to be executed. These programs
run in a queue and CPU time is shared among them. The active program gets the CPU time for a
specific period. After that is again lined up in the queue to wait for its turn again. In the meantime,
the CPU attends the next program in the queue.
Multitasking - Is the ability of any operating system to handle the execution of multiple tasks.
When a task is waiting for the completion of an activity, the CPU begins with the execution of the
next task. When a task is waiting for the user to provide inputs, another task can be uninstalling
any program/application. An example of multitasking could be a scenario where a person can
have breakfast, watch TV and talk to someone on the phone simultaneously. Here, the person are
performing more than one task simultaneously. However, at a given point in time, the person
would be taking a bite, watching the TV or speaking on the phone. The time among all the tasks
was divided. Similarly, the CPU divides the time among all the active tasks. The kernel is
responsible for scheduling the tasks.
Î Virtual Memory - Is an additional memory that an application can use when the physical memory
is already consumed. Some part of the hard disk is made available for the application, to be used
as the virtual memory. This is because to run large applications or run multiple applications at a
time, the amount of physical memory is not always be sufficient. Therefore, the system places
infrequently required programs and data in the virtual memory. The system loads the programs in
the memory, whenever required.
Î Shared Libraries - Are sets of functions or subroutines that are maintained as a set of files. With
the help of this feature, multiple applications are not required to individually maintain their code
for any function. They can access the required functions from the shared library files. This saves
hard disk space and memory.
Î POSIX Compliance - Supports most of the standards set for all UNIX systems.
Î Samba - Is derived from the Server Message Block (SMB) protocol of the Microsoft operating
systems. This feature is used to share file and print services. With the help of Samba, the user can
share a Linux file system with the Windows operating system. Alternatively it also helps users to
share the Windows file system with Linux operating system.
Note - A protocol is a set of rules that states the communication standards for data transfer
between two applications.
The term file system refers to a mechanism used by an operating system to store and manage files
and directories on a storage medium.
A partition is a logical portion of the hard disk, which is created using either the operating systembased
utility or any third-party utility.
Î Network Information Service (NIS) - Allows the creation of user accounts that can be shared
across multiple computers in a network. It is a client and server database system that acts as a
central database of account information used for account authentication.
Î Office Suites - Are supported by Linux. Basically, Linux supports OpenOffice.org, which is a set of
programs that has many built-in tools. OpenOffice.org enables a user to create documents, presentations and illustrations and also analyze data. OpenOffice.org provides a set of
applications just like Microsoft Office Application for Windows.
Î Data Archiving Utilities - Are the utilities provided by Linux for basic data backup (archiving), such
as tar, cpio and dd. Advanced Maryland Automatic Network Disk Archiver (AMANDA) is a backup
system supported by Linux. It enables the LAN administrator in setting up a master backup server
and make backup for multiple hosts in a large capacity tape drive.
Î Web Server - Linux comes with the Apache Web server, one of the most popular Web servers in
use today. In addition, Apache supports the Squid proxy server. It helps in improving the
performance for accessing the Internet.
Î Licensing - Licensing implies that anyone can download, install or use the software and any
updates to the software, regardless of the delivery mechanism. Linux is a copyright under the GNU
GPL.
Î Additional Features - Include useful and free software, such as text editors, browsers and
scientific applications.
1.6 Red Hat Operating System Distributions
Red Hat Inc. provides different variants for various types of users. It has divided its users into the following
two categories and they are as follows:
Î Business Users - The first category includes the business users requiring an operating system that
requires fewer updates. Red Hat provides the Red Hat Enterprise Linux product suite for these
users. These users require to pay a license fee for the software. The changes in the operating
system are made at a low pace so that business users are not required to upgrade the operating
system at frequent intervals.
Î Other Users - The second category includes the users who use Linux for experimental purpose
and make use of its new and advanced features. These users use the software without paying any
license fee. They can download the software from the Internet and use it free of charge. For
example, Fedora is a freely downloadable operating system.
The various Linux variants provided by Red Hat Inc. are as follows:
Î Red Hat Enterprise Linux Suite - Runs on multiple hardware architecture such as IBM PowerPC,
AMD64, Intel EM64T and Intel x86/x64. The operating systems of the Red Hat Enterprise Linux
suite are as follows:
Red Hat Enterprise Linux AS - Used for large servers and supports up to 16 CPUs. This
operating system supports databases, Enterprise Resource Planning (ERP) and Customer
Relationship Management (CRM) applications.
Red Hat Enterprise Linux ES - Used for small and middle range servers and supports up to
two CPUs. It is used for business applications, such as printing, mailing and networking
applications.
y Red Hat Enterprise Linux WS - Used as desktop operating system and supports up to two
CPUs. This operating system is compatible with Red Hat Enterprise Linux AS and Red Hat
Enterprise Linux ES. This operating system is suitable for client applications, such as
document processing and software development applications.
Î Red Hat Desktop - Is used for small and medium business groups, supporting a single CPU. It is
compatible with Red Hat Enterprise Linux AS, Red Hat Enterprise Linux ES and Red Hat Enterprise
Linux WS. This operating system is suitable for document processing, Web browsing, software
development and instant messaging.
Î Fedora Core - Represents a general-purpose operating system with capabilities comparable to
other operating systems, such as Windows NT and Macintosh. Fedora Core is a Red Hatsponsored
project but Red Hat Inc. does not support it. An individual can download Fedora free of
charge from various Web sites. The official Web site for Red Hat is http://www.redhat.com Red
Hat Enterprise Linux versions released so far are as follows:
Î Red Hat Enterprise Linux 2.1 (Panama)
Î Red Hat Enterprise Linux 3 (Taroon)
Î Red Hat Enterprise Linux 4 (Nahant)
Î Red Hat Enterprise Linux 5 (Tikanga)
Î Red Hat Enterprise Linux 6 (Santiago)
Red Hat Enterprise Linux is closely related to the Fedora Linux community project sponsored by Red Hat.
Each Red Hat Enterprise Linux version takes technologies from Fedora after considerable stabilization and
quality assurance effort. While Fedora core has a six months release cycle, RHEL has a more conservative
release cycle of two years.
Even earlier, RHEL versions were also based on Red Hat’s open source Red Hat Linux operating system. But
afterwards, Red Hat Linux split into community-based Fedora project and commercial Red Hat Enterprise
Linux. The latest RHEL 6 has many features of Fedora 13 and Fedora 14.
However, Fedora is a community project that serves as an upstream version for RHEL. RHEL serves as a
commercial enterprise operating system that is released as alpha and beta versions before final release.
As RHEL is an open source operating system and its source code can be accessed by anyone, there are
certain operating systems that use RHEL source code. Users compile their own versions of RHEL. One
such popular operating system is CentOS. These rebuilds provide free updates from non-Red Hat servers. However, these operating systems do not get any support from Red Hat.
