Basic model of a nix operating system

We can abstract the Linux OS into three operational levels or tiers, from the bottom up:

User processes: user space
The running programs that the kernel manages. Also known as the user space which is the memory that the kernal assigns for user processes. Comprising:
  • Graphical user interface
  • Servers
  • Shell
Kernel: kernel space
The core of the operating system. Software residing in memory that tells the CPU where to look for its next task. Acts as a mediator and primary interface between the hardware and the user processes. Known as kernel space: the memory that the kernel allocates for itself. Comprising:
  • System calls
  • Process management
  • Memory management
  • Device drivers
Hardware
The base: one or more CPUs and RAM memory performing computations and writing to memory. Comprising:
  • Processor (CPU)
  • Main memory (RAM)
  • Disks
  • Network ports

!! Add info on kernel mode and user mode https://www.geeksforgeeks.org/user-mode-and-kernel-mode-switching/

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