1.2 Operating system principles and common commands

Operating system principles and common commands

Operating system principle
Overview of the operating system:
Definition: The operating system is the system software that controls and manages computer hardware and software resources, and provides applications and user access.
Functions: process management, memory management, file system, device management, security, etc.
Role: coordinate and optimize computer resources, and provide a unified interface to applications.
Role: The central role of the operating system in a computer system.
Process management:
The concept of a process: an instance of a running program that has its own memory space and execution environment.
Process status: new, ready, running, blocked, terminated.
Process scheduling algorithm: first come first serve, shortest job first, priority scheduling, time slice rotation, etc.
Process communication: Mechanisms for information exchange between processes, such as shared memory, message queues, pipelines, etc.
Process synchronization: Avoid conflicts when multiple processes access shared resources, such as mutexes and semaphores.

Memory management:
The concept of memory: the main storage medium of a computer, used to store running programs and data.
Memory allocation: The operating system is responsible for allocating and reclaiming memory space to meet the needs of different programs.
Memory protection: Ensure that the memory space of each program will not be illegally accessed by other programs, improving system stability and security.
Virtual memory: The combination of physical memory and disk space enables programs to access a larger address space than physical memory.
Page replacement algorithm: used to manage the swapping in and out of pages in virtual memory. Common algorithms include LRU (least recently used) and FIFO (first in first out).

File system:
The concept of a file: a logical organization of data for storing and managing user data.
File structure: the way the operating system manages files, which can be hierarchical, flat, etc.
File operations: including operations such as creating, reading, writing, deleting, and renaming files.
Directory management: The operating system maintains the directory structure of files and supports creating, deleting, moving and searching files.
File protection: Control the access rights of files to ensure that only authorized users can access files.

Device management:
The concept of devices: various hardware devices in the computer, such as disks, printers, keyboards, etc.
Device driver: The interface through which the operating system communicates with the device and is responsible for controlling the operation of the device.
Device Allocation: Manages concurrent access to devices by multiple processes to avoid conflicts.
Interrupt handling: Handle interrupt signals generated by devices so that the operating system can respond to device state changes.

Security:
User Authentication: Ensuring that only legitimate users have access to the system, usually through username and password verification.
Access control: Control the access permissions of different users to files and resources to prevent data leakage and illegal access.
Data encryption: Protect the security of sensitive data and prevent it from being obtained by unauthorized users.
Vulnerability patching: Regularly update the operating system to patch known security holes and improve the system's resistance.

As one of the core software of the computer, the operating system plays an important role as a resource manager and an application program interface provider. Through effective process management, memory management, file system and device management, the operating system can provide a stable, efficient and safe computing environment, and provide support for the running of various applications and user operations. At the same time, with the development of computer technology, the operating system is also constantly evolving to adapt to new hardware architecture and application requirements.

Common Commands and Operations

Basic commands:
ls: List directory contents.
cd: Change directory.
pwd: Displays the current working directory.
cp: Copy a file or directory.
mv: Move a file or directory.
rm: delete a file or directory.
File and directory operations:
file creation and editing: touch, nano, vi.
File copying and moving: cp, mv.
File removal: rm.
Directory creation and management: mkdir, rmdir.
Process management command:
view process: ps, top.
Kill the process: kill.
Background execution: &.
Process priority: nice.
Network command:
Network configuration: ifconfig, ip.
View network status: netstat.
Network connection test: ping, traceroute.
System status and information:
View system information: uname, hostname.
Hardware information: lshw, lscpu.
System performance: top, htop.
Log viewing: tail, cat.
Rights management:
user and group management: useradd, userdel, groupadd.
Permission settings: chmod, chown.
File ownership: chown.

operating system principle

An overview of the operating system

The operating system is one of the core software in the computer system. Its main function is to control and manage computer hardware and software resources, and provide an operating environment for application programs. The operating system not only coordinates the work of various hardware devices, but also provides a series of system calls and interfaces, enabling applications to easily access underlying resources, shielding hardware complexity, and providing a unified user interface. The functions of the operating system include aspects such as process management, memory management, file system, device management, and security.

process management

A process is an instance of a program that is running, and each process has its own memory space, program counter, registers, etc. The operating system is responsible for the management of processes, ensuring that they can run in an orderly manner, and providing communication and synchronization mechanisms between processes. Processes have different states, including new, ready, running, blocked, and terminated. The operating system uses various scheduling algorithms to decide which process can execute, such as first come first served, shortest job first, priority scheduling, time slice round robin, etc.

Process communication is a mechanism for information exchange between multiple processes, which is especially important in multitasking and distributed systems. Common process communication methods include shared memory, message queues, pipelines, etc. The process synchronization mechanism is used to avoid conflicts when multiple processes access shared resources and ensure data consistency. Common process synchronization methods include mutexes, semaphores, and condition variables.

memory management

Memory is the main storage medium of a computer and is used to store running programs and data. The operating system is responsible for the allocation and recovery of memory to meet the memory needs of different programs. The choice of memory allocation algorithm can affect the performance and efficiency of the system. In addition, the operating system also protects the memory space of each program to prevent illegal access by other programs. Virtual memory is a common memory management technology that combines physical memory and disk space to enable programs to access a larger address space than physical memory.

The page replacement algorithm is the mechanism that manages the swapping in and swapping out of pages in virtual memory. When the physical memory is insufficient, the operating system will swap out some pages from the memory to the disk according to the page replacement algorithm to make room for new pages. Common page replacement algorithms include LRU (least recently used), FIFO (first in, first out), and OPT (optimal replacement).

File system

A file is a logical organization of data used to store and manage user data. The operating system maintains the file system and provides operations such as creating, reading, writing, deleting, and renaming files. File systems have different structures, which can be hierarchical, flat, etc. File operation is an important function in a computer system, and users and applications access data through the file system. The operating system also supports directory management, which allows files to be created, deleted, moved, and searched for better organization and management of files.

File protection is an important function of the operating system. It controls the access rights of files and ensures that only authorized users can access files. The operating system implements file protection through mechanisms such as user authentication and access control lists. Data encryption is another way to keep files secure by encrypting files to prevent unauthorized users from accessing sensitive data.

device management

Device management is another key function of the operating system, which is responsible for managing various hardware devices in the computer, such as disks, printers, keyboards, etc. Device management includes the development and maintenance of device drivers, as well as device allocation and interrupt handling. The device driver is the interface between the operating system and the device. It is responsible for controlling the operation of the device and converting the request of the operating system into hardware operation.

Device allocation is the mechanism for managing concurrent access to devices by multiple processes to avoid conflicts. Interrupt handling is the response of the operating system to the interrupt signal generated by the device, so that the operating system can process the change of the device state in time. Device management is especially important in multitasking and multi-user environments. It ensures the normal work of each device and provides reliable hardware support for applications.

safety

Security is an important feature of an operating system that protects computer systems from malware and unauthorized access. Operating systems implement security in a variety of ways, including user authentication, access control, data encryption, and vulnerability patching. User authentication is the way to ensure that only legitimate users can access the system, usually by way of username and password. Access control is to control the access rights of different users to files and resources to prevent data leakage and illegal access. Data encryption is to protect the security of sensitive data and prevent it from being obtained by unauthorized users. Vulnerability patching is to regularly update the operating system to patch known security holes and improve the system's resistance.

The security of the operating system is an important consideration in computer systems, especially in network environments. Malware and network attacks threaten the security of computer systems, and operating systems must provide multi-layered security mechanisms to protect system and user data security.

The role of the operating system

Operating system plays an important role in computer system, it is the bridge between computer hardware and application programs. The operating system coordinates and manages computer resources, provides a unified interface for application programs, shields the complexity of hardware, and makes application programs run more conveniently. The roles of the operating system include:

• Resource manager: The operating system manages various resources of the computer, including processor, memory, hard disk, network, etc. It allocates and reclaims resources, ensuring efficient use of resources.

• Task scheduler: The operating system decides which process can be executed, and uses scheduling algorithms to allocate processor time slices to ensure fairness and efficiency among multiple processes.

• Memory manager: The operating system is responsible for the allocation and recovery of memory to meet the memory needs of different programs. It also protects each program's memory space against illegal access.

• File manager: The operating system maintains the file system and supports operations such as creating, reading, writing, deleting, and renaming files. It also provides directory management to help users better organize and manage files.

• Device Manager: The operating system manages various hardware devices of the computer, including disks, printers, keyboards, etc. It is responsible for the development and maintenance of device drivers, as well as device allocation and interrupt handling.

• Security guarantor: The operating system provides a variety of security mechanisms to protect the computer system from malware and illegal access threats. It ensures that only legitimate users can access the system, controls access to files, and prevents data leakage.

The operating system plays an important role in the computer system. It provides a stable, efficient and safe computing environment, and provides support for the running of various applications and user operations. With the continuous development of computer technology, the operating system is also evolving to adapt to new hardware architecture and application requirements. Different types of operating systems have different characteristics and application fields, and choosing a suitable operating system is crucial to improving system performance and functions.

Common commands and operations in the operating system

In the field of computer science and system management, the importance of the operating system is self-evident. The operating system is a core system software that controls and manages computer hardware and software resources, and provides a unified interface for applications and users, so that the computer can work efficiently. In the operating system, we often need to use some basic commands to complete various tasks. These commands cover file and directory operations, process management, network configuration, system status viewing, and rights management. Let's take a look at some common operating system commands and what they do.

• ls (List):

The ls command is a powerful tool for listing the contents of directories. When we need to view the files and subdirectories in the current directory, the ls command is an indispensable tool. For example, if we want to see what files are in a directory, we can use the ls command to display the list of files in the directory.

Example:

ls

• cd (Change Directory):

The cd command is used to change the working directory. The cd command is very useful when we need to enter a specific directory to perform an operation. It allows us to freely switch between different directories.

Example:

cd /home/user/documents

pwd (Print Working Directory): The pwd command is used to display the full path of the current working directory. The pwd command can help us when we need to know the location of the directory we are currently working on.

Example:

pwd

• cp (Copy):

The cp command is used to copy files or directories. The cp command is indispensable if we want to copy a file or directory from one location to another.

Example:

cp source_file.txt destination/

• mv (Move):

The mv command is used to move files or directories, and can also be used to rename files or directories. When we need to move a file to another location or rename the file, the mv command is essential.

Example:

mv source_file.txt destination/
mv old_name.txt new_name.txt

• rm (Remove):

The rm command is used to delete files or directories. The rm command is a powerful tool when we need to remove files or directories that are no longer needed. But be aware that the rm command permanently deletes files, so use it with caution.

Example:

rm unwanted_file.txt

• touch:

The touch command is used to create an empty file. Sometimes we need to create an empty file as a placeholder or for other purposes, the touch command can meet this requirement.

Example:

touch new_file.txt

• nano sum vi:

nano and vi are two commonly used terminal text editors. They allow us to edit text files in the command line interface. nano is a relatively simple and easy-to-use editor, suitable for beginners. vi, on the other hand, is more powerful and flexible, but has a slightly higher learning curve.

Example:

nano my_text_file.txt
vi another_file.txt

• ps (Process Status):

The ps command is used to view the list of processes currently running on the system. We can get information about active processes in the system through the ps command.

Example:

ps

• top:

The top command is a utility for viewing processes dynamically. It will display the process status of the system in real time, including the CPU usage and memory usage of the process.

Example:

top

• kill:

The kill command is used to terminate the specified process. The kill command is a powerful tool when something goes wrong with a process or when a process needs to be stopped.

Example:

kill process_id

• ping:

The ping command is used to test the network connection with the specified host. We can use the ping command to check whether the network with other hosts is smooth.

Example:

ping google.com

• traceroute:

The traceroute command is used to trace the path of packets from the local machine to the target host. It can display the network nodes through which the data packets pass.

Example:

traceroute google.com

ifconfig and ip:

• The ifconfig and ip commands are used to view and configure network interfaces. They allow us to view the current system's network configuration as well as manipulate network interfaces.

Example:

ifconfig
ip addr show

• netstat:

The netstat command is used to display information such as network connection status and routing tables. It helps us review network activity.

Example:

netstat -a

• uname:

The uname command is used to display basic information of the system, such as operating system type, kernel version, etc.

Example:

uname -a

• hostname:

The hostname command is used to display the hostname of the current host.

Example:

hostname

• chmod:

The chmod command is used to modify the permissions of a file or directory. It helps us control access to files.

Example:

chmod 755 my_script.sh

• chown:

The chown command is used to change the owner of a file or directory. It allows us to change the owner of the file.

Example:

chown user_name my_file.txt

These commands are basic tools in the operating system, proficiency in them can improve work efficiency, and are the basis of system management and maintenance. At the same time, understanding these commands also helps to understand the working principle of the operating system and the structure of the file system. In actual work, we may frequently use these commands to perform various tasks, whether it is managing files, viewing system status or processing processes, these commands are essential. Mastering these basic commands is a necessary step for those who wish to gain an in-depth understanding of computer operating systems and system administration.

By mastering operating system principles and common commands, operation and maintenance engineers can better understand the internal mechanism of the operating system, effectively manage and maintain computer systems, and improve system stability and performance. At the same time, proficient use of common commands can improve the efficiency and accuracy of operation and maintenance work, and speed up troubleshooting and problem solving.