Basic Knowledge Introduction of UNIX

1.Concept of Operating System
The Operating system is a kind of software to manage the system resource.
In UNIX system ,there are 2 kinds of system are : System Resource and Consumers

Consumers include Users and Programs.
System Resources include Disks, Memory, CPU, Network, Printers and so on.

Operating System is just like a coordinator between these two parts. It allocates the limited resources to meet the needs of the consumers.

For example, when a User or a Program reply to store data in the Disk, the Operating System will firstly allocate a space in the disk and transfer the data from memory to Disk.

There are many kinds of OS such as : LINUX, WINDOWS ,DOS and so on.

What is UNIX?

UNIX development history

- Since late 1960s , The AT&T development of MULTICS

- In 1969 , The AT&T Bell Labs UNIX system starts

- Early 1970s , The AT&T development of UNIX system

- Mid 1970s , The University of California at Barkeley (BSD) and other universities also research and develop UNIX system.

- In Early 1980s, the Commercial interest in UNIX system

- In Early 1990s , POSIX, Standardization of the interactive user interface.

UNIX Features

The OS of UNIX is a bit different from another Operating System which has many traits and Characteristics as below ;

Multi-Tasking
Multi-User
Parallel Processing

One UNIX framework can deal with numerous number of Users, and Users can begin new jobs before old ones completion. An occupation can comprise of more than one undertaking (Ex: process) and the bury process correspondence permits undertakings to cooperate.

Pipe : The output of a process could be the input of another process
Shell : Shell characterizes the workplace, similar to the brief image, the terminal sort and even the summon use. Indeed, Shell is only the translator of the User information. UNIX underpins numerous sorts of Shells for Users..
High Security : Totally not the same as DOS and Windows, UNIX records have proprietor, and gathering qualities and diverse Users have distinctive document access consents. This exceptionally expands the security of the records.
Reliable : UNIX may be the most dependable working framework so far on the planet. Most banks, securities exchanges and telecom administrators embrace UNIX as the working framework in their exchange frameworks.
Network Oriented : UNIX bolsters a wide range of Network conventions. TCP/IP was simply put into utilization in UNIX firstly and spread to numerous fields quickly.
File System : The essential unit used to sort out data in UNIX is file.UNIX uses record framework to oversee and compose document and registry, Another utilization of record System is to deal with the User authorization.

Components of UNIX

The UNIX components including :

Kernel Services
System Call Interface
User Process

Kernel Service :

The next level provides all the kernel services

Mapping between User requests and device driver actions
The User system call is converted to a kernel service call that actually performs the requested service

-Process creation and termination

-I/O services

-File/disk access services

-Terminal handling services

System Call Interface Layer : The system call interface layer converts a process running in user mode to a protected kernel mode process

- This allows the program to invoke protected kernel routines to perform system functions

User Process Layer

The uppermost layer consists of User processes running :

- Shells

- UNIX commands

- Utility programs

- User application programs

User processes :

- Protected from other Users

- Have no access to UNIX kernel routines except through the system call interface

- Cannot directly access kernel memory space.

Conceptions of UNIX

1. Terminal :
Terminal is the hardware that we use to login UNIX. Terminal can be just a screen with a console or a complete PC framework. Content terminal is broadly utilized as a result of it is quicker than realistic terminal. Reassure is a sort of terminal with a screen.

2. Console :
Terminal is a unique terminal giving to the User to upkeep and operation of the host framework, It is made out of a screen and a console that are associated with the uncommon host interfaces (Console interface). Generally one host can just unite one Console. The console can achieve a few operations that should not be possible by conventional terminals : imperative data (for instance, discriminating issue data) must be shown on the Console and some unique errands (for instance, establishment UNIX) must be performed on the reassure. Notwithstanding the above unique capacities, the Console can work like some other terminals.

3.Device :
Device or device record alludes to some equipment, Such as a plate, a serial port and so on. UNIX gets to the equipment through device files. Device files locate under /dev.

4.Raw Device :

The device files for raw device begin with letter r. The raw device will not be accessed by UNIX, but by other applications, for example, INFORMIX directly.

5.Raw vs Cooked

Raw disk refers to a disk slice containing no file system.
Cooked disk refers to a disk that is formatted with a file system.
Common file system types on UNIX are ufs, xfs, jfs, vxfs, advfs , etc.

How to login UNIX

To work in a UNIX system, we must login into system first.

In Window98, Window Server 2000, Window Server 2003, Linux or other platforms, there are several different methods to login the remote UNIX server :

- "Telnet" command and software tools. We can use either method to login a UNIX system.

In fact, we usually use software tools to facilitate our operation. For example : We can use Teraterm or NetTerm application to login a UNIX system because these tools are more convenient to use.

-When logging in a UNIX server, we need input our account and password, if we want to logout, simply type : "exit ".