8.3. Understanding how to rebuild packages
One of the most common questions asked by Buildroot users is how to rebuild a given package or how to remove a package without rebuilding everything from scratch.
Removing a package is unsupported by Buildroot without rebuilding from scratch. This is because Buildroot doesn’t keep track of which package installs what files in the output/staging and output/target directories, or which package would be compiled differently depending on the availability of another package.
The easiest way to rebuild a single package from scratch is to remove its build directory in output/build. Buildroot will then re-extract, re-configure, re-compile and re-install this package from scratch. You can ask buildroot to do this with the make < package >-dirclean command.
On the other hand, if you only want to restart the build process of a package from its compilation step, you can run make < package >-rebuild, followed by make or make . It will restart the compilation and installation of the package, but not from scratch: it basically re-executes make and make install inside the package, so it will only rebuild files that changed.
If you want to restart the build process of a package from its configuration step, you can run make < package >-reconfigure, followed by make or make < package >. It will restart the configuration, compilation and installation of the package.
Internally, Buildroot creates so-called stamp files to keep track of which build steps have been completed for each package. They are stored in the package build directory, output/build/< package >-< version >/ and are named .stamp_< step-name >. The commands detailed above simply manipulate these stamp files to force Buildroot to restart a specific set of steps of a package build process.
Further details about package special make targets are explained in Section 8.12.5, “Package-specific make targets”.
上面提到说 Buildroot 这个工具会创建 stamp 文件来追踪某个包编译过程进行到了哪一步，上面那些命令就是修改了 stamp 文件来强制对特定包的编译重新开始。
同理，删除 stamp 文件应该可能会导致相应的模块被重新编译。
