1. A brief history of computer development
1.1 The concept of
computer Computer is the abbreviation of electronic digital computer, which is an automatic, high-speed electronic device for numerical calculation and information processing. It is mainly composed of some mechanical and electronic devices, together with appropriate programs and data. Programs and data can be automatically executed after input to solve some practical problems. Each physical entity in a computer is computer hardware; programs and data are called computer software.
A computer is a machine that can store programs and data and automatically execute programs. It is a tool that can process various digital information and assist people in acquiring, processing, storing and transmitting information.
1.2 The development history of the
computer 1.2.1 The generation of the computer
In 1822, the Englishman Charles Babbage proposed the concept of "automatic computer". In 1834, he designed the difference engine and analysis and has the basic components of modern computers. 
1.2.2 The world's first electronic computer
weighed 30 tons at the University of Pennsylvania in February 1946. It used 18,000 tubes, 70,000 resistors, and 10,000 capacitors. The power consumption was 150KW, and the operation speed was 5,000 times/second.
Tubes:
resistance:
capacitance:
1.2.3 According to the main components used, it is divided into five generations.
The first generation 1946-1958 electronic tube 5000-40000 times/second
machine language---compiling principle---assembly language for scientific computing---
second generation of advanced mathematical operation 1958-1964 Transistors Hundreds of thousands to millions of
transistors:
High-level language--vb is used for automatic control of data processing
--------- Bare metal processing
of the third generation 1964-1970 Small and medium-scale integrated circuits Millions-several millions
with operating system xp windows2000 98 95 Unix dos linux for Enterprise management and aided design
integrated circuits:
The fourth generation of large-scale and ultra-large-scale integrated circuits in the 1971-90s Millions - hundreds of millions
with software and networks used in various fields - traditional fields (Finance Government University)
The fifth generation of modern computers
combines information collection, storage, processing, communication and artificial intelligence AI with formal reasoning, association, learning and interpretation capabilities. His system structure will break through the traditional concept of von Neumann machines and achieve highly parallel processing.
1.3 Volume Classification of Computers
Microcomputers and portable computers---personal computers, PCs, etc.
Minicomputers ---processing multi-user tasks (IBM minicomputers---large hundreds of thousands of millions)
China's Internet industry has completed the IOE Environment (I--IBM minicomputer O--Oracle database E--EMC storage) openstack --- foreign core--chip (bug loophole) --- Ali Jingdong state-owned enterprise --- imitating openstack --- developing zstack
IBM Minicomputer:
Mainframe---strong operation ability but requires multiple people to handle---equivalent to the size of a cabinet (refrigerator)
Supercomputer --- used for weather forecast, nuclear test calculation --- huge amount of data processing --- coordinated by several people
1.4 Computer application field
Scientific computing
data processing
automatic control
computer aided system
logic relationship processing and artificial intelligence After learning Linux ----> artificial intelligence can also be developed based on Linux
SDN (software is scheduled for network dedicated line) ----> neural network (Part of artificial intelligence)
Computer network---Linux must be a network foundation
1.5 The development trend of computer
intelligence
is to require computers to simulate human thinking functions and senses, to have the ability to recognize sounds and images, and to have the functions of reasoning and associative learning.
Networking ---- Rarely use router servers enough to simulate routers, switches, firewalls, etc.
Baidu --- Public network IP really exposes the server to the public network iptables firewalld Policy routing
refers to the use of communication technology and computer technology to disperse different Computers at the location are interconnected and communicate with each other according to network protocols, so that all users can share software, hardware and data resources.
Megaization
refers to a computer system with a storage capacity of hundreds of megabytes or more, a computing speed of more than trillions per second, and complete peripheral equipment. Megaization is mainly used for research and development of cutting-edge science and technology and military defense systems.
The miniaturized
computer is further developed towards the direction of high-speed integration, that is, the computer physical devices are getting smaller and smaller, and the computing speed of the computer is faster and the function is stronger.
Multimedia
Multimedia computer is the product of the combination of computer technology and television audio-visual technology. It integrates various media and is widely used in entertainment, auxiliary teaching and engineering simulation.
Second, the hardware basic
computer --- notebook desktop
Server---1U 4U---dell server (U means thickness, 1U=4.445cm) The company usually uses 1-2U 
for a computer/server, which is composed of many parts. Only when these parts work together in coordination, is it called for the computer. Mainly include: motherboard, CPU, memory, hard disk, sound card, graphics card and so on.
2.1 Computer components
2.1.1 Power supply --- The power supply of the heart
protection computer The
server generally provides dual power supply for
personal computer power supply:
Server Power:
2.1.2 Mainboard---
All the boards of the skeleton must function through the mainboard. The
mainboard is composed of different architecture standards and various main components and interfaces. The
interface type---IDE eliminates the SATA interface for personal computers and is used by enterprises. SAS SCSI iSCSI
2.1.3CPU central processing unit---brain mainstream cpu i7----virtualization version 7 and above is the best Apple ultrabook office U low-voltage
control center responsible for computing and control, the most critical part of the computer is
more capable than any component Determines the working speed and efficiency of the computer. It is
called a great engineer and a great device. It also needs a thinkpad.
2.1.4CPU fan----Choose the fan---Copper and aluminum
to cool down the CPU, the computer crashes and restarts is the CPU temperature is too high
2.1.5 The motherboard chipset
is the most important component on the motherboard, responsible for managing the CPU and memory, various bus expansions, and peripheral support
2.1.6 The BIOS chip
is responsible for the self-inspection, setting, and saving of each component after the motherboard is powered on, and the operating system can only be started when everything is normal. It records the most basic information of the computer and is the most basic bridge between software and hardware. Without it, the computer cannot work.
Three common BIOSes: Award, AMI, Phoenix
2.1.7 Bus expansion slots
are divided into memory slots, graphics card slots, etc. according to their functions.
Various I/O interfaces: tape--hard disk, keyboard, mouse, printer, USB ( Universal Serial Bus), etc.
2.1.8 Hard Disk ---- Disk management classification SCSI SATA IDE SSD Operation and maintenance 128GSSD 500 or so
large-capacity storage --- LVM RAID card in enterprises,
especially in server optimization scenarios, the performance of the hard disk is the decision Important factors for website performance
SSD hard disk: 
2.1.9 The memory stick
is a temporary storage, which is only responsible for the transfer of computer data and cannot be permanently saved. Capacity and processing speed directly determine the speed of computer data transmission. Together with CPU and hard disk, they are called the three major components of a computer.
Memory is generally 4G 8G 16G
2.1.10 Other
sound cards, optical drives, graphics cards, etc.
3. Overview of operating systems and Unix systems
3.1 What is an operating system In
simple terms, an operating system is a tool or program that communicates information between users and hardware. For example, the XP
operating system (OS, Operationg System) is the basic system software in the electronic computer system that is responsible for supporting the application program operating environment and the user operating environment, and is also the core of the computer system.
The operating system is the interface between the user and the computer, as well as the interface between the computer hardware and other software. The functions of the operating system include managing the hardware, software and data resources of the computer system, controlling the operation of the program, improving the human-machine interface, providing support for other application software, making all the resources of the computer system work to the greatest extent, and providing various forms of user interface.
Application software provides support to maximize the use of all resources of the computer system, provide various forms of user interfaces, enable users to have a good working environment, and provide necessary services and corresponding interfaces for the development of other software. In fact, the user does not need to touch the operating system. The operating system manages the computer hardware resources, and at the same time allocates resources according to the resource request of the application, such as dividing CPU time, opening up memory space, calling printers, etc. 
At present, the more common operating systems on the microcomputer (PC server) are DOS, Windows, Unix, Linux, etc.
3.2 What is Unix=====> The earliest use of charges is used in enterprises to develop according to their own environment ----> external Vend
is a powerful multi-user, multi-tasking operating system that supports multiple processor architectures, first developed at AT&T's Bell Labs in 1969 by Ken Thompson, Dennis Ritchie, and Douglas McIlroy.
After long-term development and night, it has now become the mainstream operating system. Because Unix has the characteristics of mature technology, high reliability, strong network and database functions, outstanding scalability and good openness, it can meet the actual needs of all walks of life and was once the first choice of operating system.
3.3 History of Unix Development
IV. Introduction to Linux
4.1 Linux Introduction and History
Linux is a set of free-to-use and open-source Unix-like operating systems that can be distributed freely.
Linux is known for its efficiency and flexibility. It can realize all the Unix features on the PC computer, and has the ability of multi-tasking and multi-user. Linux is freely available under the GNU Public License.
Linux is loved for two main reasons:
One is that it is free software, and users can get it and its source code without paying anything. And you can make necessary modifications to him according to your own needs, use it free of charge, and spread it without restrictions
Another reason, with all the features of Unix, anyone who uses Unix operating system or wants to learn Unix operating system can get
4.2GNU and GPL knowledge from Linux
Free Software Foundation (FSF) ---> GNU Project (purpose is to make software and systems free) --->
The main project of GPL agreement FSF is GNU, the goal is to establish a freely distributed and portable Unix-like operating system; GNU project software includes: Emacs editing software (similar to Vim editor) , gcc compiled software, bash command interpreter and programming language, etc.;
the core idea of GPL license is to ensure the freedom to share and modify free software, and anyone has the right to obtain, modify and redistribute the source code of free software, but requires Can't post specific changes.
4.3 Linux advantages
1) Unix system clone on PC system, imitating Unix kernel construction, backward compatible with Unix instruction set
2) Perfect multi-user, multi-task, multi-process system
3) High system stability and reliability
4) High system security
5) Perfect network services: HTTP, FTP, SMTP, POP, SAMBA, SNMP, DNS, DHCP, SSH, TELNET, etc.
6) GNU open system
7) A large number of third-party free applications
8 ) Supported by many industry manufacturers: IBM, ORACLE, INTEL, HP, Google, etc.
9) Complete large-scale database platform: ORACLE, DB/2, MySQL and other
Internet companies are dominated by MySQL in traditional industries (Finance Government University---Oracle)
10) Complete GUI: GNOME, KDE---software (graphical software)
11) Perfect development platform: C/C++ embedded, java-tomcat/resin, Perl/shell python
4.4 Linux version https://www.kernel.org/
1) Linux operating system = kernel + system software + application
2 ) Linux kernel (kernel) version cat /etc/redhat-release
3) Linux distributors: Redhat, Debian, Fedora, CentOS, Ubuntu, SUSE, OpenSUSE, red flag, etc...
4) Redhat no longer follows from 9.0 GPL, is a paid product, but still open source (open source code)
for companies and enterprises. 6.5 6.8--stable version
7.3 is mainly
4.4 Graphical desktop support
1) X Windows system
2) GNOME
3) KDE
general production scene operation and maintenance, Neither use the desktop environment, nor even install the desktop package, except for some special software requirements (ORACLE requires VNC)
4.5 Linux system current application field
1) IT server Linux system application
RHEL enterprise version is charged for the
community version free
The IT server field is mainly Linux, Unix, and Windows, with Linux gradually occupying a dominant position
Linux is widely used as an enterprise-level server. Using Linux system, you can build www server, database server, proxy server (cluster server), mail server, transparent gateway, router, etc. 2) In the
field of embedded system applications,
due to the open source code of the Linux system, it is powerful, reliable, stable and flexible. And it has great scalability, coupled with its extensive support for a large number of microprocessor architectures, hardware devices, graphics support and communication protocols, therefore, in the field of embedded applications, from Internet devices (routers, switches, firewalls) , load balancer) to dedicated control systems (mobile phones, PDAs, various household appliances), the Linux operating system has a large application market.
In particular, after several years of development, Linux has successfully entered the mainstream embedded development platform. For example, in the field of smart phones, Linux has firmly occupied a place in the development platform of smart phones after fierce competition with Windows Mobile and Symbian, forming a tripartite confrontation.
3) The application field of personal desktop system
is the computer system we use in the office. The support of the Linux system in this regard is also very good: common applications:
browser Internet browsing---firefox supports Firefox browser (built-in)
office software---open office imitates compatible Microsoft office to
send and receive emails-- -webmail
real-time communication---qq msn, etc.
text editing---vim Emacs, etc.--similar to word
multimedia applications---camera printer
Although the Linux personal desktop system has been widely supported, the Linux personal desktop system is in the desktop market The share is far from being able to compete with windows. The biggest obstacle is not the Linux desktop system product itself, but the user's concept of use, operating habits and application skills, as well as the porting of software that has been developed on windows. It will take some time before the Linux desktop system is popularized.
Install the system ok? RHEL6.5 bridging (physical network card ip address 192.168.1.200)
configure yum source After the
configuration network card
takes effect, the default noboot parameter defaults to no
bootPROTO default dhcp
---- In the enterprise, the application server is all fixed IP,
close the firewall ,
close the selinux
connection Xshell
modification hostname hosts file
--------- take a snapshot - there is a problem later to restore the snapshot (back to this time)
Pdf--->
WinSCP--->
Used to transfer files across systems, in special cases (generally install lrzsz software rz upload sz download)
Xshell--->
Xmind---> mind mapping software
comparison tool---> shell script for comparison
!