UNIX/Linux 系统管理技术手册阅读（四）

UNIX/Linux 系统管理技术手册阅读（四）

2016.8.14 21:40-22:101.3 FRICTION BETWEEN UNIX AND LINUX1.3 UNIX和Linux之间的摩擦  Because they are similar, this book covers both UNIX and Linux systems. Unfortunately, mentioning UNIX and Linux together in the same sentence can sometimes be like stepping into a political minefield, or perhaps blundering into a large patch of quicksand. But since the relationship between UNIX and Linux seems to engender some confusion as well as animosity, it’s hard to avoid staking out a position. Here is our perspective and our short version of the facts.  因为UNIX和Linux系统颇为相似，所以本书会同时讲解这两种系统的管理。遗憾的是，在一句话里同时用UNIX和Linux这两个称谓，就仿佛一脚踏入了政治漩涡，或许也像是陷入了一大片泥潭。不过，既然UNIX和Linux之间的关系似乎呈现出某些混淆和冲突，所以要避开不谈我们的立场也比较困难。下面是我们的观点，还有我们对事实的简要说明。  Linux is a reimplementation and elaboration of the UNIX kernel. It conforms to the POSIX standard, runs on several hardware platforms, and is compatible with most existing UNIX software. It differs from many—but not all—variants of UNIX in that it is free, open source, and cooperatively developed. Linux includes technical advances that did not exist in UNIX, so it is more than just a UNIX clone. At the same time, traditional UNIX vendors have continued to refine their systems, so there are certainly areas in which commercial UNIX systems are superior to Linux.  Linux重新实现并优化了UNIX内核。Linux遵循POSIX标准，能够在几种硬件平台上运行，兼容现有的大多数UNIX软件。它同大多数（但不是全部）别的UNIX变体不一样，区别之处在于，它是自由的，开放源代码的，而且是由成百上千不同的个人和组织无私奉献协同开发出来的。与此同时，传统的UNIX厂商则继续改善自己的系统，所以肯定存在一些领域，在这些领域内，商业UNIX系统比Linux强。  Whatever the relative merits of the systems, Linux is a legally, developmentally, and historically distinct entity that cannot properly be referred to as “UNIX” or as a “version of UNIX.” To do so is to slight the work and innovation of the Linux community. At the same time, it’s somewhat misleading to insist that Linux is “not UNIX.” If your creation walks like a duck and quacks like a duck, you may have invented a duck.  无论两种系统有什么相对而言的优缺点，Linux从法律上、从开发上以及从历史上看，都和UNIX有着明显的区别，因此不能把Linux称为UNIX，或者UNIX的一种版本。这样做会忽视Linux社区所做的工作和创新。同时坚持认为Linux不是UNIX的话，又会有点误导性。如果做出来的东西走路像鸭子，叫起来也像鸭子，那或许可以说，造的就是鸭子！这是的意思是，不能因为Linux像UNIX，就把Linux当成UNIX。

2016.8.15 15:20-16:20  Schisms exist even within the Linux camp. It has been argued, with some justification, that referring to Linux distributions simply as “Linux” fails to acknowledge the work that went into the software that runs outside the kernel (which in fact constitutes the vast majority of software on an average system). Unfortunately, the most commonly suggested alternative, GNU/Linux, has its own political baggage and has been officially endorsed only by the Debian distribution. The Wikipedia entry for “GNU/Linux naming controversy” outlines the arguments on both sides.1 Interestingly, the use of open source software is now predominant even on most UNIX systems, but no one seems to be pushing for a GNU/UNIX designation just yet.  即便在Linux阵营里也存在分歧。有人举证说，把Linux发行版简称为“Linux”，那么开发人员在内核这外运行的那些软件（在一般系统上实际是很大一部分软件）上投入工作，就没得到承认。偏偏不巧，最常推荐的替代称谓“GNU/Linux”也有其自己的政治包袱，所以只有Debian这个发行版才正式采用它。维基百科上有关“GNU/Linux命名争议”的条目列举出了争执双方的论点。有意思的是，现如今，甚至在大多数UNIX系统上，也是开源软件的使用占据主导，但还没有人提“GNU/Linux”这样的说法。  Linux software is UNIX software. Thanks largely to the GNU Project, most of the important software that gives UNIX systems their value has been developed under some form of open source model The same code runs on Linux and nonLinux systems. The Apache web server, for example, doesn’t much care whether it’s running on Linux or Solaris. From the standpoint of applications and most administrative software, Linux is simply one of the best-supported and most widely available varieties of UNIX.  Linux软件就是UNIX软件。多亏了GNU计划，使UNIX系统更富价值的重要软件大多都以某种开源源代码的形式被开发出来。在Linux和非Linux系统上运行的代码是相同的。比如说：Web服务器Apache俨然不在意它是在Linux上还是在HP-UX上运行。从应用软件的角色来看，Linux只不过是得到最好支持的UNIX变体之一罢了。  It’s also worth noting that Linux is not the only free UNIX-like operating system in the world. OpenSolaris is free and open source, although its exact licensing terms have earned suspicious looks from some open source purists. FreeBSD, NetBSD, and OpenBSD—all offshoots of the Berkeley Software Distribution from UC Berkeley—have ardent followers of their own. These OSes are generally comparable to Linux in their features and reliability, although they enjoy somewhat less support from third-party software vendors.  另外还值得一提的是，Linux不是现今世界唯一的自由UNIX版本。OpenSolaris系统也是自由和开源的，虽然在某些讲求纯开源的人眼里来看，它的许可证条款存有疑点。FreeBSD、NetBSD和OpenBSD--都是从UC Berkeley（加州大学伯克利分校）的BSD（伯克利软件发布，即Berkeley Software Distribution）发展而来的分支--都有其各自的热诚追随者。虽然这些操作系统从第三方软件厂商得到的支持有点少，但它们在功能和可靠性上却往往可以同Linux相媲美。  UNIX and Linux systems have both been used in production environments for many years, and they both work well At this point, the choice between them has more to do with packaging, support, and institutional inertia than any real difference in quality or modernity.  UNIX和Linux系统用于生产环境已经有许多年了，而且它们都表现不错。现在要在它们之间做出选择，更多考虑的是软件打包机制、能获得的支持以及使用习惯的惰性，而不是品质或者成熟度实际有什么样的差别。  In this book, comments about “Linux” generally apply to Linux distributions but not to traditional UNIX variants. The meaning of “UNIX” is a bit more fluid, as we occasionally apply it to attributes shared by all UNIX derivatives, including Linux (e.g., “UNIX file permissions”). To avoid ambiguity, we usually say “UNIX and Linux” when we mean both.  本书对“Linux”的评论一般也都适用于各种Linux发行版本，但不适用于传统的UNIX变体。“UNIX”的含义稍有点儿多变，因为我们偶尔也会用在包括Linux在内的所有UNIX变体所共有的属性上（例如，“UNIX文件权限”）。为了避免混淆，在想表达二者都有的情况下，我们通常说“UNIX和Linux”。

2016.8.16 16:50-17:20

1.4 LINUX DISTRIBUTIONS

1.4 Linux的发行版本

All Linux distributions share the same kernel lineage, but the ancillary materials

that go along with that kernel can vary quite a bit. Distributions vary in their

focus, support, and popularity. There continue to be hundreds of independent Linux distributions, but our sense is that distributions based on the Debian, Red Hat, and SUSE lineages will continue to predominate in production environments over the next five years.

所有的Linux发行版本共享相同的内核源，但是和内核一起的辅助软件则随着发行版本的不同而有很大不同。各发行版本在其侧重点、支持和流行程度上有所不同。独立的Linux发行版本在数据上仍然有数百种之多，但是我们觉得，未来5年内，基于Debian,Red Hat和SUSE源的那些发行版本将在生产环境中占据优势地位。

The differences among Linux distributions are not cosmically significant. In fact,

it is something of a mystery why there are so many different distributions, each

claiming “easy installation” and “a massive software library” as its distinguishing features. It’s hard to avoid the conclusion that people just like to make new Linux distributions.

各种Linux发行版本之间存在差别，但是差别没有大到远隔千山万水的地步。实际上，为什么会有这么多不同的发行版本，而每种发行版本都把“易于安装”和“海量软件库”作为其特色来宣传，这就挺难解释的。于是难免会得出这样的结论，人们只是喜欢“做”出新的Linux发行版而已。

Many smaller distributions are surprisingly competitive in terms of fit and finish.

All major distributions, including the second tier, include a relatively painless installation procedure, a well-tuned desktop environment, and some form of package management. Most distributions also allow you to boot from the distribution DVD, which can be handy for debugging and is also a nice way to take a quick look at a new distribution you are considering.

许多较小的发行版本在成熟度和完善性方面极具竞争力。所有的主流发行版本，包括二线的发行版本，都有相当简便的安装步骤、调配良好的桌面环境，以及某种形式的软件包管理机制。大多数发行版还可以让用户从DVD光盘上直接启动，这对于调试来说很方便，而且还是一种对关注的新发行版很快了解的好办法。

Since our focus in this book is the management of large-scale installations, we’re

partial to distributions such as Red Hat Enterprise Linux that take into account

the management of networks of machines. Some distributions are designed with

production environments in mind, and others are not. The extra crumbs of assistance that the production-oriented systems toss out can make a significant difference in ease of administration.

既然我们在本书中所关注的是大规模安装的管理问题，那么我们就会侧重考虑像RHEL（Red Hat Enterprise Linux）这样用于管理计算机网络的发行版本。有些发行版本的设计考虑到了生产环境，其他的发行版则没有。面向生产环境的系统所提供的额外支持功能，对于方便系统管理工作来说，带来了巨大的不同。

When you adopt a distribution, you are making an investment in a particular vendor’s way of doing things. Instead of looking only at the features of the installed software, it’s wise to consider how your organization and that vendor are going to work with each other in the years to come.

当用户采用了一种发行版之后，就是在某个特定发行商的做事方式上进行投资。不要只看到软件安装以后的功能，而是要明知地考虑到，自己的单位和那家发行商要在未来的数据年里共事。

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