The Filesystem Hierarchy Standard is a document that specifies the layout of directories on a Linux system. The FHS was devised to provide a common layout to simplify distribution-independent software development. The FHS specifies the following directories (taken directly from the FHS specification):

• / (the root directory)
• /boot (static files of the boot loader)
• /dev (device files)
• /etc (host-specific system configuration)
• /lib (essential shared libraries and kernel modules)
• /mnt (mount point for mounting a filesystem temporarily)
• /opt (add-on application software packages)
• /sbin (essential system binaries)
• /tmp (temporary files)
• /usr (secondary hierarchy)
• /var (variable data)