Things always have a core, complex things can always be modular and hierarchical, as well as embedded Linux. The difficulty of learning embedded Linux is mainly due to the fact that there are too many knowledge and concepts involved, that is, it is more complicated. Therefore, learning embedded Linux needs to find the core, it needs to be modular, and it needs to be divided into layers.
The modular processing of embedded Linux system can be divided into Bootloader, Kernel, fs, Shell, Gui, and Embeded Sql . The above is the seven important modules of the embedded Linux system, through which you can develop a variety of applications (applications). For example, a web browser for surfing the Internet, an audio player for playing a song, a video player for playing a movie, various games (such as Lianliankan), and the like.
Embedded Linux System - The boot program, that is, the bootloader and PC's BIOS programs are some types, the biggest is used to install the system, just like the PC you just bought if you do not have to install the operating system, you need to install the operating system, PC installation Windows operation The system usually starts from the optical drive, press Fn key to enter the installation mode to read the disc and start the installation process. Embedded Linux is similar to this, Bootoader presses any key (U-boot) to enter the installation mode during startup, except that the installation does not read the system from the optical drive, but reads the system from the serial port (UART) or network port. In addition, there is a different PC installation file system included in the system, the embedded Linux system operating system and file system are separate and need to be installed separately.
Embedded Linux system - Kernel, or Kernel, is the core of a Linux system. Kernel contains drivers, network protocols, memory management, file systems, and process management modules. These concepts are relatively abstract and will be developed in the Windows operating system. Having encountered similar module partitioning, if only the Windows operating system users rarely need to have these concepts, but you are using these things in your use. If the external expansion device needs to install additional drivers, you need to use the driver program. When you open the office, you use the file system. You use the Internet protocol to access the Internet. At the same time, you can open the TTP and the calculator. Use process management. These concepts of the original embedded Linux system have long existed in the Windows operating system. It is like encountering a familiar person who wanted to ask "We seem to have seen it there."
Embedded Linux system - file system, fs, is an important part of the Linux system, the file system is mainly implemented by the folder and file operations (such as create, delete, open, close, read and write, etc.), which and Windows operations The system's file system is similar. The file system module in the embedded Linux system usually needs Kernel support, and contains the Shell command package, which means that the embedded Linux file system not only provides support for file operations, but also provides support for the Shell package. You may have doubts about what is Shell, please look down.
Embedded Linux system - The command line, that is, the shell is an important part of the operating system, of course, also includes embedded Linux system. In the Windows operating system, open "Start", click "Run", enter "cmd" and press "Enter". You will enter a window interface of "Comparative Soil". This interface is just a shell. Enter "ipconfig" You can see the IP information of this PC. Embedded Linux system also has a similar shell, but not mapped to the machine (such as ARM hardware board), but mapped to the serial port terminal of the PC (here concept is more, it is recommended to remember "map" "ARM board", "PC machine", "serial terminal" these keywords), that is, through the serial port terminal of the PC can operate embedded Linux shell, such as input "ifconfig" you can view the ARM hardware board IP information, this and the above "ipconfig" has the same effect.
Embedded Linux system - graphics library, Gui is used to support the graphics surface of the library. For example, the "desktop" and "desktop" icons under the Windows system are all implemented using a graphics library. The background picture of your mobile phone display, the phone number shown, and the text message are all based on the graphic library. Embedded Linux system does not necessarily use the graphics library, so the graphics library is one of the modules that can be tailored to the embedded Linux system. The current popular graphics library is QT/miniGUI/GTK+2/MFC, which can be used in addition to MFC. Linux system.
The embedded Linux system-embedded database, Embeded Sql, is another important module of the embedded Linux system. It means that some embedded Linux system products may be used, some may not be used, and the most popular embedding is currently. The database is Sqlite. So what does an embedded database do? If you know about a database, you can think of an embedded database as a small, lightweight database. If you do not understand, please consider the transcripts (tables) of a class. Each student’s grades are viewed and ranked. If you do a transcript, you will be equivalent to depositing a database. The viewing process is equivalent to searching (retrieving) the database. The result of the review is like when searching (searching), ranking is equivalent to indexing the database members by order. The point of simplicity - "The database is the operation of tables and tables."