4.2 安裝軟體的各種方式介紹

通常要在 UNIX® 系統上安裝軟體時，有幾個步驟要作：

如果一切順利的話，就這麼簡單。如果在安裝非專門設計(移植)給 FreeBSD 的軟體時出問題， 那可能需要修改一下它的程式碼，才能正常使用。

當然，我們可以在 FreeBSD 上使用上述的傳統方式來安裝軟體，但是，我們還有更簡單的選擇。 FreeBSD 提供了兩種省事的軟體管理機制： packages 和 ports。就在寫這篇文章的時候， 已經有超過 16,000 個 port 軟體可以使用。

所謂的 FreeBSD package 就是別人把該應用程式編譯、打包完畢。 該 package 會包括該應用程式的所有執行檔、設定檔、文件等。 而下載到硬碟上的 package 都可透過 FreeBSD 套件管理指令來進行管理，比如： pkg_add(1)、pkg_delete(1)、pkg_info(1)等指令。 所以，只需簡單打個指令就可輕鬆安裝新的應用程式了。

而 FreeBSD port 則是用一些檔案，來自動處理應用程式的安裝流程。

請記住：如果打算自己來編譯的話，需要執行很多操作步驟(下載、解壓、patch、編譯、安裝)。 而 port 呢，則是涵蓋所有需要完成這些工作的必備步驟， 所以只需打一些簡單的指令，那些原始程式碼就會自動下載、解壓、patch、編譯，直至安裝完畢。

事實上，ports 機制還可以用來產生 packages，以便他人可以用 pkg_add 來安裝，或是稍後會介紹到的其他套件管理指令。

而 packages 以及 ports 它們都是一樣會認 dependencies(軟體相依關係)。 假設：您想安裝某程式，但它有相依另一個已裝的函式庫(library)， 而在 FreeBSD 的 port 以及 package 都有這程式以及該函式庫了。 所以無論是用 pkg_add 指令或者 port 方式來裝該程式， 這兩者(package、port)都會先檢查有沒有裝該函式庫，若沒有就會自動先裝該函式庫了。

這兩種技術都很相似，您可能會好奇為什麼 FreeBSD 會弄出這兩種技術來呢。 其實，packages 和 ports 都有它們各自的長處，使用哪一種完全取決於您自己的喜好。

Package 好處在於：

• A compressed package tarball is typically smaller than the compressed tarball containing the source code for the application.

• Packages do not require any additional compilation. For large applications, such as Mozilla, KDE, or GNOME this can be important, particularly if you are on a slow system.

• Packages do not require any understanding of the process involved in compiling software on FreeBSD.

Ports 好處在於：

• Packages are normally compiled with conservative options, because they have to run on the maximum number of systems. By installing from the port, you can tweak the compilation options to (for example) generate code that is specific to a Pentium IV or Athlon processor.

• Some applications have compile time options relating to what they can and cannot do. For example, Apache can be configured with a wide variety of different built-in options. By building from the port you do not have to accept the default options, and can set them yourself.

  In some cases, multiple packages will exist for the same application to specify certain settings. For example, Ghostscript is available as a ghostscript package and a ghostscript-nox11 package, depending on whether or not you have installed an X11 server. This sort of rough tweaking is possible with packages, but rapidly becomes impossible if an application has more than one or two different compile time options.

• The licensing conditions of some software distributions forbid binary distribution. They must be distributed as source code.

• Some people do not trust binary distributions. At least with source code, you can (in theory) read through it and look for potential problems yourself.

• If you have local patches, you will need the source in order to apply them.

• Some people like having code around, so they can read it if they get bored, hack it, borrow from it (license permitting, of course), and so on.

To keep track of updated ports, subscribe to the FreeBSD ports mailing list and the FreeBSD ports bugs mailing list.

The remainder of this chapter will explain how to use packages and ports to install and manage third party software on FreeBSD.