Introduction to linux [Reading Notes], Introduction to linux

Introduction to linux [Reading Notes], Introduction to linux

Linux is one of the Unix-like operating systems; it is not a commercial operating system; its source code is open under the GUN Public License.

Linux Kernel features:

Monolithic kernel)

Compiled and statically connected traditional Unix kernels (for module Support)

Kernel thread

Multi-thread application support (a standard thread consists of thread ID, current Instruction Pointer (PC), register set and stack)

Preemptible Kernel

Multi-processor support

File System

STREAMS

The operating system is a collection of basic programs, the most important of which is called the kernel. When the operating system is started, the kernel is loaded into RAM, and the kernel contains many core processes necessary for system operation.

The operating system must fulfill two main objectives:

Interacts with hardware to provide services for all underlying programmable components on the hardware platform

Provides an execution environment for applications (so-called User Programs) running on computer systems

The hardware introduces at least two different execution modes for the CPU: the user program's non-privileged access mode and the kernel's privileged mode. Unix divides them into user and kernel states.

Multi-user system

It is a computer that can concurrently and independently execute several applications belonging to two or more users ." Concurrency "thinks these applications can be active at the same time and compete for various resources ." "Being independent" means that each application can execute its own tasks without considering what other applications are doing.

Multi-user operating systems must have the following features:

Authentication mechanism for verifying user identity

Protection mechanisms that prevent erroneous user programs from interfering with the running of other applications in the system

Protection mechanisms to prevent malicious user programs from interfering with or spying on activities of other users

The billing mechanism that limits the number of resources allocated to each user

It is very important to distinguish between programs and processes: several processes can concurrently execute the same program, while the same process can smoothly execute several programs.

Because the explicit message transmission between different layers of the operating system takes a certain cost, such an operating system is generally less efficient than a single kernel.

Single Kernel: Each kernel layer is integrated into the entire kernel program.

The Linux Kernel provides modules. Advantages:

Modular Approach ---- platform independence ---- saving memory usage ---- No performance loss

 

 

 

 

 

 

 

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