Building a root file system from scratch is definitively a complex task because several well known directories must be created and populated with a lot of files that must follow some standard rules. Usually, it's a good idea to start with a pre-packaged root file system, in order to skip the actual ''creation'' step, and letting you to work on the ''customization'' of the file system.You have two options:

# start from a big file system and remove all the components (packages, libraries, application binaries, ..) that you don't need# start from a small file system and add all the components (packages, libraries, application binaries, ..) that you need  If you want prefer to build a the entire root file system, there are several possibilities that are described in the following sections.