Yocto - 使用Yocto开发嵌入式Linux系统_07 构建使用的临时文件夹

Detailing the Temporary Build Directory

在本章中，我们将尝试了解映像生成后临时构建目录的内容，并了解 BitBake 如何在烘焙过程中使用它。此外，我们还将了解这些目录中的某些内容如何在出现问题时作为有价值的信息来源来帮助我们。

In this chapter, we will try to understand the contents of the temporary build directory after image generation and see how BitBake uses it in the baking process. In addition, we will learn how some of these directories can assist us by acting as a valuable source of information when things do not work as expected.

1，Detailing the build directory 

构建目录是每个 Poky 用户的中心信息和工件源。其主要目录如下

The build directory is a central information and artifact source for every Poky user. Its main directories are as follows:

* conf： 这里包含我们用来控制 Poky 和 BitBake 的配置文件。我们在第 2 章 “构建基于 Poky 的系统 ”中首次使用了该目录。它存储了一些配置文件，如 build/conf/local.conf 和 build/conf/bblayers.conf。

* downloads：存储所有下载的工件。它起到下载缓存的作用。我们曾在第 5 章 “掌握 BitBake 工具 ”中详细介绍它。

* sstate-cache： 它包含打包数据的快照。它主要用于加速未来的编译过程，因为它被用作编译过程的缓存。该文件夹在第 7 章 “理解打包支持”中有详细介绍。

* tmp：这是临时构建目录，也是本章的重点。

* conf: This contains the configuration files we use to control Poky and BitBake. We first used this directory in Chapter 2, Baking Our Poky-Based System. It stores configuration files, such as build/conf/local.conf and build/conf/bblayers.conf.

* downloads: This stores all the downloaded artifacts. It works as a download cache. We talked about it in detail in Chapter 5, Grasping the BitBake Tool.

* sstate-cache: This contains the snapshots of the packaged data. It is a cache mainly used to speed up the future build process, as it is used as a cache for the building process. This folder is detailed in Chapter 7, Assimilating Packaging Support.

* tmp: This is the temporary build directory and the main focus of this chapter.

2，Constructing the build directory

在前几章中，我们从抽象的概要上详细了解了 Poky 的输入和输出。我们已经知道，BitBake 使用元数据生成不同类型的人工制品，包括映像。除了生成的工件，BitBake 还会在此过程中创建其他内容，这些内容可根据我们的目标以多种方式使用。

In the previous chapters, we learned about Poky’s inputs and outputs in abstract high-level detail. We already know that BitBake uses metadata to generate different types of artifacts, including images. Besides the generated artifacts, BitBake creates other content during this process, which may be used in several ways, dependent on our goals.

在编译过程中，BitBake 会执行多项任务并不断修改编译目录。因此，我们可以按照通常的 BitBake 执行流程更好地理解它，如下所示：

BitBake performs several tasks and continuously modifies the build