Linux was first released into an unsuspecting world in the summer of 1991.Linux refers only to an operating system kernel originally written by Linus Torvalds. The Linux kernel provides a variety of core system facilities required for any system based upon Linux to operate correctly. Application software relies upon specific features of the Linux kernel, such as its handling of hardware devices and its provision of a variety of fundamental abstractions, such as virtual memory, tasks (known to users as processes), sockets, files, and the like. The Linux kernel is typically started by a bootloader or system firmware.
The term “Linux” has become somewhat overloaded in everyday commu-nication. In large part, this is due to its growing popularity—people might not know what an operating system kernel is or does, but they will have perhaps heard of the term Linux. In fact, Linux is often used interchangeably in reference to the Linux kernel itself, a Linux system, or an entire prebuilt (or source) software distribution built upon the Linux kernel and related software. Such widely varying usage can lead to difficulties when providing technical explanations. For example, if you were to say, “Linux pro-vides TCP/IP networking,” do you mean the TCP/IP stack implementation in the Linux kernel itself, or the TCP/IP utilities provided by a Linux distribution using the Linux kernel, or all of the above?
The broadness of the usage of the term has led to calls for a greater distinction between uses of the term “Linux.” For example, Richard Stallman and the Free Software Foun-dation often prefix “GNU/” (as in “GNU/Linux”) in order to refer to a complete system running a Linux kernel and a wide variety of GNU software. But even terms such as these can be misleading—it’s theoretically possible to build a complete Linux-based system without GNU software (albeit with great difficulty), and most practical Linux systems make use of a variety of both GNU and non-GNU software.
Despite the con-fusion, as more people continue to hear of Linux, the trend is toward a generalization of the term as a reference to a complete system or distribution, running both GNU and non-GNU software on a Linux kernel. The most famous desktop linux distributions are Red Hat Enterprise Linux (RHEL), SuSE Linux Enterprise Server (SLES), Ubuntu Linux, or Debian GNU/Linux.And all of these provide the user with a pre-packaged, shrinkwrapped set of files and an installation procedure to get the kernel and various overlaid software installed on a certain type of hardware for a certain pur-pose.
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