title: How to use grub2-extra-lua module
body: <p>I googled for grub2-lua, but found very few information on it.
  I can't find an official website for grub2-lua (i.e official source code tarball download link), except for a git clone link.</p>
  
  <p>Moreover, I can't find any documentation about grub lua. So I don't know how to use it.</p>
  
  <p>I managed to compile grub2 along with lua module, then I boot into grub and type "help lua" to try to get some help info. But it only says that I can use command "lua script_file.lua" to execute the lua script. So I just want to learn the details on how to use lua module. For example, how to execute lua commands in grub.cfg file, how to return the lua execution result to the grub.cfg file, and what APIs does grub provide to the lua module.</p>
  
  <p>The reason why I use lua module is that I have the need of file system operations in grub (i.e. mv, cp, cd, pwd, mkdir, rm, nano commands). grub2 itself doesn't provide this functionality. Some posts said grub-extra-lua module may provide this feature.</p>
  
  <p>So I just want to know how to use grub lua module to operate on files and directories.</p>