什么是 Linux ？
Linux 是自由／开源软件吗？
从哪里获取 Linux?
Linux 内核是自由／开源软件，在 GNU 一般公共许可（GNU General Public License, GPL）下发布。但是，不同的 Linux 发行版本包含着不同的组件，其中一些可能不是自由／开源软件。例如，德国的 SuSE Linux 版本就包含有非自由／开源的 YaST （Yet another Setup Tool）安装程序。
Debian GNU/Linux [87] 是少数几个承诺在核心系统中只包括自由／开源软件组件（根据 OSI 的定义）的发行版本之一。
The Linux kernel is FOSS, licensed under the GNU General Public License. However, different distributions of Linux contain different components, some of which are not FOSS. For example, the German SuSE Linux distribution includes the non-FOSS YaST (Yet another Setup Tool) installation program.
The Debian GNU/Linuxi distribution is one of the few distributions that are committed to including only FOSS components (as defined by the Open Source Initiative) in its core distribution.
Linux 是当今大众媒体中关于自由／开源软件最热门的字眼。但是 Linux 这个词在被广泛使用的同时其含义也越来越宽泛。在关于自由／开源软件的讨论中，了解 Linux 的不同定义是非常重要的。
=作为内核的 Linux=
Linux 最初是 Linus Torvalds 开发的操作系统内核的名字。内核是操作系统的核心部分，它控制中央处理器，管理内存和硬件设备。操作系统内运行的不同程序也需要内核来协调和通信。一些 BSD 版本使用的 Mach 内核也是自由／开源核心中的一种。
核心在某种程度上是可以更换的。大多数自由／开源应用很容易就可以在 Mach 内核，Linux 内核甚至实验性的 GNU Hurd 内核上运行。但是，内核的类型对性能和自由／开源系统硬件平台的兼容性有很大影响。例如，尚不成熟的 GNU Hurd 内核只能在 x86 （PC）架构上运行。Linux 内核已被移植到几乎所有的计算架构上，包括 PlayStation 2 [85]，大型机和嵌入式设备。
=作为发行版的 Linux =
Linux 如今更普遍地用于指称一个内容远不止于内核的 Linux 发行版本。Linux 发行版本（有时被称为 GNU/Linux 以强调 GNU 项目的巨大贡献）包括作为心脏的 Linux 核心以及所有用于实现完整操作系统功能的自由／开源软件组件，包括系统函数库，图形用户界面，各种数据库，网页服务器，email 程序，等等。同样的组件也包含在其他自由／开源的甚至是私有的操作系统中。例如 Linux 和 BSD 缺省的图形服务器 XFree86 也被用于私有的 Unix 系统，如 Solaris，HP-UX 和 IBM 的 AIX 系统。
新闻报道“慕尼黑最终倾向于 Linux”[86] 中的 Linux 是指包括字处理、绘图和 email 软件的发行版本。虽然 Linux 内核二进制文件的长度只占整个 Linux 发行版本的 0.25％，其重要性足以让整个发行版本被称为 Linux。
世界上没有统一的 Linux 发行版本。虽然所有的发行版本都包含 Linux 内核，但它们包括的自由／开源应用软件和配置都各有不同。Linux 有许多商业发行版本，其中一些可以免费获取，还有大量的定制发行版本满足不同用户的独特需求。虽然不同 Linux 发行版本的自由／开源内容大都相同，它们也对从高端服务器到桌面系统甚至嵌入式系统等不同的用途进行了优化。本地化的发行版本至少包括字体、输入法和必要的地区语言菜单翻译。
Linux is the most frequently heard FOSS buzzword in the mass media today. However, because of its common usage, the term Linux has been used to refer to broader and broader definitions. It is important to understand the different definitions of Linux to be able to follow the discussions on FOSS.
Linux as the kernel
Linux was originally the name of the kernel created by Linus Torvalds. A kernel is the critical center point of an operating system that controls CPU usage, memory management and hardware devices. It also mediates communication between the different programs running within the operating system. There are other FOSS kernels, including the Mach kernel that is the core of some of the BSD distributions.
Kernels are to a certain extent interchangeable. Most FOSS applications will run on a Mach kernel, Linux kernel or even the experimental GNU Hurd kernel, without too much difficulty. However, the kernel type greatly influences performance and the hardware platforms that the FOSS system can run on. For instance, the less mature GNU Hurd kernel can run only on the x86 (PC) architecture. The Linux kernel has been ported to run on almost any computing architecture, including the Playstation 2i, mainframes and embedded devices.
Linux as a distribution
The more common usage of Linux today refers to a Linux distribution, which includes far more than the kernel. The Linux distribution (sometimes referred to as the GNU/Linux distribution in recognition of the GNU Project’s significant contribution) contains the Linux kernel at its heart and all the FOSS components required to produce full operating system functionality. This includes the system libraries, GUI, various databases, web servers, email utilities, and others. These same components are also often found on other FOSS and even on proprietary operating systems. For instance, XFree86 is the default GUI foundation in Linux and BSD. XFree86 is also used on proprietary Unix systems such as Solaris, HP-UX and IBM’s AIX system.
Reports that say “Munich May Opt for Linux After All”ii refer to the Linux distribution, including word processing, printing and email software. Even though the Linux kernel forms less than 0.25 percent (binary file size) of a Linux distribution, its functionality is critical enough to allow the entire distribution to be called Linux.
There is no single Linux distribution. While all distributions contain the Linux kernel at its heart, the FOSS applications included and the configurationssupported vary. There are multiple commercial distributions, several freely available, and numerous customized distributions that are targeted to the unique needs of different users. While the FOSS contents of different Linux distributions are mostly identical, they are optimized for different uses such as for high-end servers, user-friendly desktops or even embedded systems. Localized distributions at a minimum include the fonts, input methods and menu translations necessary to use the software in the regional language.
二进制和源代码形式的自由／开源软件都可以从因特网免费下载。Linux 核心可以从 http://www.kernel.org/ 下载，其它应用程序也有各自的站点。但是，大部分用户倾向于获取整套 Linux 发行版本。下表列出了一些最知名的 Linux 发行者：
| 知名 Linux 发行者 | |
|---|---|
| Debian | www.debian.org |
| Redhat | www.redhat.com |
| SuSe | www.suse.com |
| Mandrake | www.mandrakelinux.com |
| SlackWare | www.slackware.com |
| TurboLinux | www.turbolinux.com |
从供应商处获取 Linux 成套发行版本的好处有很多。成套的 Linux 相对于“组装”的 Linux 最大的好处是节省了用户的时间：
FOSS, in binary and source code format, is free and downloadable from the Internet. The Linux kernel itself can be downloaded from http://www.kernel.org and other applications from their respective websites. However, most users tend to obtain distributions of Linux. The following is a table of some of the most popular distributors of Linux:
Popular Linux Distributors
Debian
www.debian.org
Redhat
www.redhat.com
SuSe
www.suse.com
Mandrake
www.mandrakelinux.com
SlackWare
www.slackware.com
TurboLinux
www.turbolinux.com
The advantages of going with distributions of Linux are many. The single most important advantage of vendor Linux over “stock” Linux is that it saves users time:
Download time: The Linux operating system and complementary software involve large files and long download times. A standard 56kbps modem would take at least 45 days to download a standard 3 CD distribution. Vendors also provide bundled software—browsers, server applications, office suite, etc.—that saves the users from the tedious work of hunting and downloading individual software packages.
Installation and compiling time: Many FOSS packages are downloadable only as source code. Users are required to compile and install the software themselves, assuming they are competent enough to do so. On a slow computer, compilation of source code may take days or even weeks. Vendor distributions of Linux often come precompiled and packaged with an easy installation system that takes less than an hour to install on most modern systems.
Quality assurance: Vendors typically perform extensive testing to ensure that all of the components work well together. Since FOSS projects are developed independently, there is always the chance that changes in one package have outdated another package. Vendors resolve these dependencies for the user, supplying an integrated package that works “out of the box”.
Learning time: Vendors provide manuals and publish reference material (for sale) for their products, making Linux much easier for the average user to learn.