UNIX/Linux 系統管理技術手冊閱讀（四）

2016.8.14 21:40-22:10
1.3 FRICTION BETWEEN UNIX AND LINUX
1.3 UNIX和Linux之間的摩擦
  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.
  因為UNIX和Linux系統頗為相似，所以本書會同時講解這兩種系統的管理。遺憾的是，在一句話里同時用UNIX和Linux這兩個稱謂，就仿佛一腳踏入了政治漩渦，或許也像是陷入了一大片泥潭。不過，既然UNIX和Linux之間的關系似乎呈現出某些混淆和沖突，所以要避開不談我們的立場也比較困難。下面是我們的觀點，還有我們對事實的簡要說明。
  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重新實現并優化了UNIX內核。Linux遵循POSIX標準，能夠在幾種硬件平臺上運行，兼容現有的大多數UNIX軟件。它同大多數（但不是全部）別的UNIX變體不一樣，區別之處在于，它是自由的，開放源代碼的，而且是由成百上千不同的個人和組織無私奉獻協同開發出來的。與此同時，傳統的UNIX廠商則繼續改善自己的系統，所以肯定存在一些領域，在這些領域內，商業UNIX系統比Linux強。
  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.
  無論兩種系統有什么相對而言的優缺點，Linux從法律上、從開發上以及從歷史上看，都和UNIX有著明顯的區別，因此不能把Linux稱為UNIX，或者UNIX的一種版本。這樣做會忽視Linux社區所做的工作和創新。同時堅持認為Linux不是UNIX的話，又會有點誤導性。如果做出來的東西走路像鴨子，叫起來也像鴨子，那或許可以說，造的就是鴨子！這是的意思是，不能因為Linux像UNIX，就把Linux當成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陣營里也存在分歧。有人舉證說，把Linux發行版簡稱為“Linux”，那么開發人員在內核這外運行的那些軟件（在一般系統上實際是很大一部分軟件）上投入工作，就沒得到承認。偏偏不巧，最常推薦的替代稱謂“GNU/Linux”也有其自己的政治包袱，所以只有Debian這個發行版才正式采用它。維基百科上有關“GNU/Linux命名爭議”的條目列舉出了爭執雙方的論點。有意思的是，現如今，甚至在大多數UNIX系統上，也是開源軟件的使用占據主導，但還沒有人提“GNU/Linux”這樣的說法。
  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軟件就是UNIX軟件。多虧了GNU計劃，使UNIX系統更富價值的重要軟件大多都以某種開源源代碼的形式被開發出來。在Linux和非Linux系統上運行的代碼是相同的。比如說：Web服務器Apache儼然不在意它是在Linux上還是在HP-UX上運行。從應用軟件的角色來看，Linux只不過是得到最好支持的UNIX變體之一罷了。
  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.
  另外還值得一提的是，Linux不是現今世界唯一的自由UNIX版本。OpenSolaris系統也是自由和開源的，雖然在某些講求純開源的人眼里來看，它的許可證條款存有疑點。FreeBSD、NetBSD和OpenBSD--都是從UC Berkeley（加州大學伯克利分校）的BSD（伯克利軟件發布，即Berkeley Software Distribution）發展而來的分支--都有其各自的熱誠追隨者。雖然這些操作系統從第三方軟件廠商得到的支持有點少，但它們在功能和可靠性上卻往往可以同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系統用于生產環境已經有許多年了，而且它們都表現不錯。現在要在它們之間做出選擇，更多考慮的是軟件打包機制、能獲得的支持以及使用習慣的惰性，而不是品質或者成熟度實際有什么樣的差別。
  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.
  本書對“Linux”的評論一般也都適用于各種Linux發行版本，但不適用于傳統的UNIX變體。“UNIX”的含義稍有點兒多變，因為我們偶爾也會用在包括Linux在內的所有UNIX變體所共有的屬性上（例如，“UNIX文件權限”）。為了避免混淆，在想表達二者都有的情況下，我們通常說“UNIX和Linux”。

2016.8.16 16:50-17:20

1.4 LINUX DISTRIBUTIONS

1.4 Linux的發行版本

  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發行版本共享相同的內核源，但是和內核一起的輔助軟件則隨著發行版本的不同而有很大不同。各發行版本在其側重點、支持和流行程度上有所不同。獨立的Linux發行版本在數據上仍然有數百種之多，但是我們覺得，未來5年內，基于Debian,Red Hat和SUSE源的那些發行版本將在生產環境中占據優勢地位。

  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.

  各種Linux發行版本之間存在差別，但是差別沒有大到遠隔千山萬水的地步。實際上，為什么會有這么多不同的發行版本，而每種發行版本都把“易于安裝”和“海量軟件庫”作為其特色來宣傳，這就挺難解釋的。于是難免會得出這樣的結論，人們只是喜歡“做”出新的Linux發行版而已。

  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.

  許多較小的發行版本在成熟度和完善性方面極具競爭力。所有的主流發行版本，包括二線的發行版本，都有相當簡便的安裝步驟、調配良好的桌面環境，以及某種形式的軟件包管理機制。大多數發行版還可以讓用戶從DVD光盤上直接啟動，這對于調試來說很方便，而且還是一種對關注的新發行版很快了解的好辦法。

  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.

  既然我們在本書中所關注的是大規模安裝的管理問題，那么我們就會側重考慮像RHEL（Red Hat Enterprise Linux）這樣用于管理計算機網絡的發行版本。有些發行版本的設計考慮到了生產環境，其他的發行版則沒有。面向生產環境的系統所提供的額外支持功能，對于方便系統管理工作來說，帶來了巨大的不同。

  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.

  當用戶采用了一種發行版之后，就是在某個特定發行商的做事方式上進行投資。不要只看到軟件安裝以后的功能，而是要明知地考慮到，自己的單位和那家發行商要在未來的數據年里共事。