2016.8.31 10:00-10:30

1.12 WAYS TO FIND AND INSTALL SOFTWARE

Chapter 12, Software Installation and Management, addresses software provisioning in detail. But for the impatient, here’s a quick primer on how to find out what’s installed on your system and how to obtain and install new software.

1.12 查找和安装软件的途径

  第12章详细讲述了软件方面的知识。但是对于没有耐性的读者来说，这一节是个初级速成教材，教给读者怎样知道自己系统上已经安装好的软件有哪些，以及怎样获得和安装新软件。

Modern operating systems divide their contents into packages that can be installed independently of one another. The default installation includes a range of starter packages that you can expand according to your needs.

  现代操作系统把自己分成多个软件包，软件包可以逐个独立安装。默认安装的只包括一定范围的起步软件包，用户可以根据需要再扩充。

Add-on software is often provided in the form of precompiled packages as well, although the degree to which this is a mainstream approach varies widely among systems. Most software is developed by independent groups that release the software in the form of source code. Package repositories then pick up the source code, compile it appropriately for the conventions in use on the systems they serve, and package the resulting binaries. It’s usually easier to install a systemspecific binary package than to fetch and compile the original source code. However, packagers are sometimes a release or two behind the current version.

  附加软件常常也以预先编译好的软件包形式提供，这是一种主流的方式，各个系统间的区别仅仅在于程序不同。大多数软件都是由独立的小组开发，且以源代码的形式发布出来。接下来，软件库收集这些源代码，然后根据软件库为之服务的系统上的使用习惯，对其进行编译，再把编译结果打成软件包。安装针对特定系统的二进制软件包通常要比取得并编译原来的源代码更容易。不过，打包软件有时候要比当前版本落后一两个版本号。

The fact that two systems use the same package format doesn’t necessarily mean that packages for the two systems are interchangeable. Red Hat and SUSE both use RPM, for example, but their filesystem layouts are somewhat different. It’s best to use packages designed for your particular system if they are available.

  两种系统使用相同的软件打包系统不一定意味着两个系统的软件包能互换使用。例如，Red Hat和SUSE都使用RPM，但是它们的文件系统布局却稍有不同。如果能找到专为自己系统做的软件包，那就用它们，这是最好的做法。

Major Linux distributions provide excellent package management systems that include tools for accessing and searching Internet software repositories. Distributors aggressively maintain these repositories on behalf of the community, so there is rarely a need for Linux administrators to step outside the bounds of their systems’ default package manager. Life is good.

  主流的Linux发行版本都提供优异的软件包管理体系，里面包括能够访问和搜索Internet上软件库的工具。发行商替社区积极维护这些软件库，所以Linux系统管理员很少需要跳出自己系统上的默认软件包管理器。生活真美好。

UNIX systems show more ambivalence about package management. Solaris, HPUX, and AIX all provide packaging software that works at the level of individual machines. However, the vendors of these systems don’t maintain repositories of open source software, so the user communities are mostly left to fend for themselves.9 Unfortunately, one of the main pieces of glue that holds a packaging universe together is a way for packages to reliably refer to other packages in order to express dependency or compatibility information. Without some central coordination, the whole ecosystem can quickly fall apart.

  UNIX系统在软件包管理方面显得畏手畏尾。Solaris、HP-UX和AIX都提供打包软件，在单机的层次上使用没问题。但是，这些系统的厂商却没有维护开源软件库，而让用户群大多进行自我维护。遗憾的是，维系一个打包软件环境所依赖的纽带之一，是有一条途径可以让软件包可靠地检索其他软件包，从而掌握依赖性和兼容性方面的信息。没有某种中心作为协调，整个体系就会很快分崩离析。

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UNIX/Linux 系统管理技术手册阅读（九）