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UNIX/Linux 系统管理技术手册阅读(四)


2016.8.14 21:40-22:10
1.3 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.
  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.
  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.

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.
  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.
  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.
  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.

2016.8.16 16:50-17:20


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.


  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.


  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.


      本文转自cix123  51CTO博客,原文链接:http://blog.51cto.com/zhaodongwei/1837888,如需转载请自行联系原作者


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stat 显示指定文件的相关信息  cd /home/itcast  stat familyA who、w 显示在线登录用户  who whoami 显示用户自己的身份 hostname 显示主机名称  hostname  hostname -i 显示主机IP uname 显示系统信息  uname -a 显示全部信息 top 显示当前系统中耗费资源最
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