As we discussed previously, Linux has a hierarchical filesystem. The files and directories form a tree structure, in accordance with the Filesystem Hierarchy Standard (FHS). The topmost directory is the root directory / and all directories are contained within or below this directory in the hierarchy. There are several directories within the root directory – called subdirectories – that are generated upon installation of a Linux distribution. Many of these are used exclusively by the system. There are also some generated for use by users, where subdirectories can be created without elevated permissions.

The FHS includes descriptions of the core directories in the hierarchy, causing this structure to be relatively standard across Linux systems. The table provides a list of the major subdirectories of the root directory /. There is no need to remember the purpose of every directory unless you are working at a lower level within a Linux system. Rather, this table should give you an idea of the basic layout of a Linux filesystem and possibly serve as a useful reference in the future.

Most of the work you do will likely be performed in your home directory while on a Linux system, while programs you use will reside in other locations, as explained above. You may want to familiarize yourself with the Stampede3 Filesystem as well as how to navigate it if you are planning on doing work there. Also feel free to peruse Optional Topics in a later section for more information on the root user and mounts.