15.2 Structure of File System
Here, we will take a look at the basic structure of file system in the Raspberry Pi system. The Raspberry Pi system has a built-in file system that is created by default when the system is installed, and users manage their own data within these file systems.
15.1.4 Review of Special Device
15.1.4.1 Booting SD Card
The default Debian distribution consists of two partitions on the SD card. The first partition is 75 MB in VFAT format, a format for Microsoft’s removable devices. It has the files needed to configure Raspberry Pi and files to load Linux itself, and is mounted as “/boot” after booting. The second partition is much larger in the EXT4 format, the default format for fast access and data reliability in Linux. All other programs, user-installed programs, and user data are all stored here. It occupies most of the SD card.
15.1.3 Mounting Device
15.1.3.1 Meaning of Mount
On Linux systems, all files used on the system are supposed to belong to a file hierarchy, one large tree type with root (/) at the top. These files may appear to be in one hierarchy, but may actually be scattered across a variety of devices.
15.1.2 Formatting Disk
15.1.2.1 What Is Formatting Disk?
After a partition is created for a disk, the partition must be initialized to a specific file-system, and this initializing process is format. When you format a partition, a specific file-system is determined for that partition, and a master directory is created that manages all the directorys and files that will be stored on that partition.
15.1 Management of Logical Storage Device
15.1.1 Partition Management
A disk can be divided into partitions that are spaces managed independently and divided logically. Partitions are also called “disk slices” or “disklabel”. The result of partitioning is managed by partition table in sector 0 of disk.
Chapter 15 Storage Device and Filesystem
Chapter’s Main Topics
This chapter describes the basic concepts of storage devices used to store data and how to manage storage devices by partitions, and explains how the structure of the file system provided by the Raspbian operating system basically is configured.
It includes descriptions on the following topics:
■ Logical storage device
■ Partition management
■ Format disk
■ Mount devic
■ Structure of file system
14.2.2 USB Device and Device File
14.2.2.1 USB Device and “/dev” File
A USB device is a bus type device. In Raspberry Pi system, USB device is managed by “/dev/bus/usb” folder. If you look inside the 001 folder, you will see the following files. File names are in the form of 001 ~ 016, which means the device number of USB device. You can see that you have a one-to-one correspondence with the USB device that you inquired before with the “lsusb” command.
14.2 USB Device
14.2.1 “lsusb” Command – Confirm USB Device
You can use the “lsusb” command to see what USB devices are installed in Raspberry Pi system.
14.1.4 Network Device
14.1.4.1 Characteristics of Network Device
In Linux, a network device is thought of as an entity that sends and receives data packets. A network device is usually a physical device, such as an Ethernet card. However, there are some network devices defined with only software, such as loopback device that is used to send data to itself.
14.1.3 Block Device
14.1.3.1 Block Device Characteristics
The block device inputs and outputs data in unit of block when processing data in the device, and increases the processing performance by placing a intermediate buffer.