Operation Manual

The directories visible on the default Debian distribution are as follows:
• boot—This contains the Linux kernel and other packages needed to start the Pi.
• bin—Operating system-related binary files, like those required to run the GUI, are stored here.
• dev—This is a virtual directory, which doesn’t actually exist on the SD card. All the devices connected to the system—
including storage devices, the sound card and the HDMI port—can be accessed from here.
• etc—This stores miscellaneous configuration files, including the list of users and their encrypted passwords.
• home—Each user gets a subdirectory beneath this directory to store all their personal files.
• lib—This is a storage space for libraries, which are shared bits of code required by numerous different applications.
• lost+found—This is a special directory where file fragments are stored if the system crashes.
• media—This is a special directory for removable storage devices, like USB memory sticks or external CD drives.
• mnt—This folder is used to manually mount storage devices, such as external hard drives.
• opt—This stores optional software that is not part of the operating system itself. If you install new software to your Pi, it will
usually go here.
• proc—This is another virtual directory, containing information about running programs which are known in Linux as
processes.
• selinux—Files related to Security Enhanced Linux, a suite of security utilities originally developed by the US National
Security Agency.
• sbin—This stores special binary files, primarily used by the root (superuser) account for system maintenance.
• sys—This directory is where special operating system files are stored.
• tmp—Temporary files are stored here automatically.
• usr—This directory provides storage for user-accessible programs.
• var—This is a virtual directory that programs use to store changing values or variables.
Physical Layout
Although the preceding list is how the file system appears to the Linux operating system, it’s not how it’s laid out on the SD card
itself. For the default Debian distribution, the SD card is organised into two main sections, known as partitions because they split
the device into different areas in much the same way as the chapters of this book help to organise its contents.
The first partition on the disk is a small (75 MB) partition formatted as VFAT, the same partition format used by Microsoft
Windows for removable drives. This is mounted, or made accessible, by Linux in the /boot directory and contains all the files
required to configure the Raspberry Pi and to load Linux itself.