The BitBake metadata has thousands of variables, but the scope where these variables are available depends on where it is defined. Basically, there are two kinds of variables as follows:

• Variables defined in configuration files are global to every recipe. The parsing order of the main configuration files is shown as follows:
  • build/conf/local.conf
  • <layer>/conf/machines/<machine>.conf
  • <layer>/conf/distro/<distro>.conf
• Variables defined within recipe files are local to the specific recipe only during the execution of its tasks