Linux is a free-to-use and freely distributed Unix-like operating system. It is a multi-user, multi-tasking, multi-threaded and multi-CPU based operating system based on POSIX and UNIX. It runs major UNIX tools, applications, and network protocols. It supports both 32-bit and 64-bit hardware. Linux inherits Unix's network-centric design philosophy and is a stable multi-user network operating system. The Linux operating system was born on October 5, 1991 (this is the first official release time). There are many different Linux distributions for Linux, but they all use the Linux kernel. Linux can be installed on a variety of computer hardware devices, such as mobile phones, tablets, routers, video game consoles, desktop computers, mainframes, and supercomputers. Strictly speaking, the word Linux itself only refers to the Linux kernel, but in fact people have become accustomed to using Linux to describe the entire operating system based on the Linux kernel and using GNU engineering tools and databases.

Linux is a free-to-use and freely distributed Unix-like operating system. It is a multi-user, multi-tasking, multi-threaded and multi-CPU based operating system based on POSIX and UNIX. It runs major UNIX tools, applications, and network protocols. It supports both 32-bit and 64-bit hardware. Linux inherits Unix's network-centric design philosophy and is a stable multi-user network operating system. The Linux operating system was born on October 5, 1991 (this is the first official release time). There are many different Linux distributions for Linux, but they all use the Linux kernel. Linux can be installed on a variety of computer hardware devices, such as mobile phones, tablets, routers, video game consoles, desktop computers, mainframes, and supercomputers. Strictly speaking, the word Linux itself only refers to the Linux kernel, but in fact people have become accustomed to using Linux to describe the entire operating system based on the Linux kernel and using GNU engineering tools and databases.

There are two operating systems: MMU and MMU. The MMU is Windows, MacOS, Linux, Android, and the MMU is FreeRTOS VxWorks ucOS. There are two kinds of CPUs: with MMU and without MMU, with MMU with Cortex-A series ARM9, ARM11 series, without MMU with Cortex-M series. STM32 is an M series, which is a low-cost design. Without an MMU controller, it is impossible to run Linuxuc. μClinux is not Linux.

Therefore, based on the STM platform and meeting the real-time control requirements of the operating system, only the following five options are available for porting. They are μClinux, μC/OS-II, eCos, FreeRTOS and rt-thread.

Seeing this may have friends wonder why μClinux does not belong to Linux? Let me briefly explain the difference between the two:

In terms of hardware support, since μClinux inherits most of the performance of Linux, it requires at least 512KB of RAM space and 1MB of ROM/Flash space.

In the porting of μClinux, μClinux is an improvement of Linux for embedded systems, and its structure is more complicated. To port μClinux, the target processor needs to have enough external ROM and RAM in addition to the processor-related code.

The biggest feature of μClinux is that it is designed for non-MMU processor. This is suitable for stm32f without MMU function, but porting this system requires at least 512KB of RAM space, 1MB of ROM/FLASH space, and stmf103 has 256K of FLASH. External memory, which increases the cost of hardware design. μClinux is complex in structure, relatively difficult to port, and has a large kernel. Its real-time performance is also poor. If the embedded products developed are focused on file systems and network applications, μClinux is a good choice.

Standard Linux is designed for processors with MMUs. On this processor, the virtual address is sent to the MMU, which maps the virtual address to a physical address. Supports protection between different tasks by giving different virtual-to-physical address translation mappings for each task.

uClinux is an embedded Linux operating system for control. It derives from the Linux 2.0/2.4 kernel and follows most of the features of mainstream Linux. Suitable for microprocessors/microcontrollers that do not have a memory management unit (MMU). No MMU support is the basic difference between uClinux and mainstream Linux.

uClinux has a very small kernel and user software space. Developers familiar with mainstream Linux will notice small differences in working under uClinux, but they can also quickly become familiar with some of the features of uclinux. For developers who design kernel or system space applications, pay special attention to uClinux's neither memory protection nor virtual memory model. In addition, some kernel system calls are different.

For uCLinux, it is designed for processors without an MMU and cannot use the processor's virtual memory management technology. uCLinux still uses memory paging management, and the system pages the actual memory at startup. The program is paged when the application is loaded. However, since there is no MMU management, uCLinux actually uses a real memory management strategy. The uCLinux system's access to memory is straightforward, and the addresses accessed in all programs are the actual physical addresses. The operating system has no protection for memory space, and each process actually shares a running space. Before a process is executed, the system must allocate enough contiguous address space for the process and then load it into the contiguous space of main memory.

Can stm32 run linux?

　　
Therefore, μClinux does not belong to Linux, so STM32 cannot run linu.

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