Shell Environment

Virtual Console

A virtual console (VC) – also known as a virtual terminal (VT) – is a conceptual combination of the keyboard and display for a computer user interface. It is a feature of some operating systems  such as Linux and UNIX in which the system console  of the computer can be used to switch between multiple virtual consoles to access unrelated user interfaces.

When the any Linux system first boots up, you get a normal Linux login: prompt, so you can log in, and GUI or CLI or do whatever else you would do with a single Linux shell.

 Note -:  The graphical X Window System starts in the seventh virtual console. To access 6 terminal press and hold [CTRL] + [ALT] +F {1, 2, 3, 4, 5, 6}. For example press CTRL+Alt+F1 (or ALT+F1) to CTRL+Alt+F7

Access X GUI system
To access X GUI system press CTRL+ALT+F7

 

Access CLI system

To access CLI system press CTRL+ALT+F1

Apart from the fact that you use the same screen and keyboard, each virtual console is quite independent.

Logging Interface in Linux (GUI, CLI)

Depending on how you have set up your system, you will either have a graphical login Screen or a Text-Based logging prompt for you to perform the login process.

Now we have to put User Name and Password.

Text Base Logging-:

Now we have to put User Name and Password

Linux is Multiuser, Multitasking Operating System HOW ?

A single user operating system provides the facilities to be used on one computer by only one user. In other words, it supports one user at a time. However, it may support more than one profile. Single keyboard and single monitor are used for the purpose of interaction. The most common example of a single user operating system is a system that is found in a typical home computer.

There are two general types of single-user operating system:

1. Single tasking

2. Multitasking systems

Single tasking systems are the systems which are designed to manage the computer so that one user can effectively do one thing at a time.

The Palm OS for Palm hand held computers is a good example of a modern single-user, 
single-task operating system. DOS is also one the examples.

Multitasking operating system allows more than one program to be running at the same time, from the point of view of human time scales. A single-tasking system has only one running program. 

Multi-tasking can be of two types: 

1. Pre-emptive

2. Co-operative 

In pre-emptive multitasking, the operating system slices the CPU time and dedicates one slot to each of the programs. Unix-like operating systems such as Solaris and Linux support pre-emptive multitasking.

 Cooperative multitasking is achieved by relying on each process to give time to the other processes in a defined manner.

Multi-user

A multi-user operating system allows multiple users to access a computer system at the same time. Time-sharing systems and Internet servers can be classified as multi-user systems as they enable multiple-user access to a computer through the sharing of time. Single-user operating systems have only one user but may allow multiple programs to run at the same time.

Linux, UNIX, VMS and mainframe operating systems.

User interaction with linux Environment

Linux Terminal  -: 

   Symbol, "#", is the last character in the prompt when you are logged in as root. This is true whether you logged in as root as we are seeing in screen   And $", is the last character in the prompt when you are logged in as a normal user.

What is the difference between the Admin user, Root and standard users?

• The main difference between the different classes of users is based on what permissions that user has.

• Normal users can only affect their own files, where the Admin user can affect some system files.

• The root user has the ability to control anything, including files owned by other users. Because of the power the root user has, the root user can only access the server using SSH, and does not have FTP or Email access.