
Mastering Embedded Linux Programming
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The idea of a build system is to automate all the steps I have described up to this point. A build system should be able to build, from upstream source code, some or all of the following:
The toolchain
The bootloader
The kernel
The root filesystem
Building from an upstream source is important for a number of reasons. It means that you have peace of mind that you can rebuild at any time, without external dependencies. It also means that you have the source code for debugging and that you can meet your license requirements to distribute that to users where necessary.
Therefore to do its job, a build system has to be able to do the following:
Download a source from upstream, either directly from the source code control system or as an archive, and cache it locally
Apply patches to enable cross compilation, fix architecture-dependent bugs, apply local configuration policies, and so on
Build the various components
Create a staging area and assemble a root filesystem
Create image files in various...