 Welcome to session that is on introduction to shell architecture and the basic commands. These are the learning outcomes. At the end of this session, students will be able to describe a Linux caller architecture and the command. So now before starting to the Linux, so we will see what is Linux. In the simple language, the Linux is an operating system. We all are familiar with the other operating system such as Microsoft Windows, Apple, macOS, iOS, Google Android, etc. Just like them, Linux is also an operating system. An operating system is the software that enables communication between the computer hardware and the software. It conveys input to get processed by the processor and bring output to the hardware to display it. This is the basic function of an operating system. Next, Linux is was developed in the mid 90s. It can be used to form a Wishrockets or a super computers. It is everywhere in our phones, laptop, PCs, cars, and even in the refrigerators. It is very much famous among the developers and the normal computer users. So we will now see the components of Linux operating system. As an operating system is the collection of a software each designed for this specific function. Linux OS has the following components, that is the kernel, kernel modules, hardware, and the Linux operating system consists of a system software, user process, user utility, and compilers. So now we will see what do we mean by the kernel. Kernel is the main heart of the operating system. It is the main core of the operating system. It establishes the communication between the devices and the software. Moreover, it manages the system resources. Basically, it has four responsibility, that is a device management, memory management, a process management, and the handling system calls. So first we will see what you mean by the device management. A system has a many devices connected to it like CPU, memory devices, sound cards, graphic cards, etc. A kernel stores all the data related to the devices in the device driver. Without this kernel won't be able to control the device. Thus the kernel allows what a device can do and how to manipulate it to bring out the best performance. It also manages the communication between all the devices. The kernel has certain rules that has to be followed by the all devices. Next we will see the memory management. Another function that kernel has to manage is the memory management. Kernel keeps the track of use and unused memory and makes sure that the process should not manipulate the data of each other using virtual memory address. Next is the process management. In the process management, the kernel assigns enough time and give priorities to the process before handling the CPU to other process. It also deals with the security and the ownership of information. Next the handling system call. The handling system calls means the programmer can write a query or ask the kernel to perform a task. Next after kernel the second most important is the system libraries. A system library is a special program that help us in accessing the kernel features. A kernel has to be triggered to perform a task and this triggering is done by the application. But application must know how to place a system call because each kernel has a different sets of system calls. A programmer have to develop a standard library of procedures to communicate with kernel. Each operating system supports these standards and these are transferred to the system calls for that the operating system. Most well known system library for Linux is GLIBC that is GNU C library. Next is the system tools. Linux OS has a set of utility tools which are usually simple commands. It is the software which is GNU project has written and published under this open source license so that the software is freely available to the everyone. With the help of commands you can access your files, edit, manipulate the data in your directories or files, change location or files or anything. Next is the end user tool. This end user tool makes a system unique for the user. Each tools are not required for an operating system but necessary for a user. Some example of the end tools are graphic design tools, office suits, browsers, multimedia players and etc. So this was about the components of the Linux system. Next we are going to see the architecture of an Linux OS system. So this is an architecture. So architecture consists of three main levels that is hardware, kernel and shell. So the Linux system basically works on the four layer. First view in the diagram below which is showing the architecture of Linux system that is an hardware. So this is an hardware. So the hardware consists of all physical devices attached to the system. For example, hard disk drive, RAM, motherboard, CPU, etc. Next is the kernel. Kernel is a core component of any Linux operating system which is directly interacts with the hardware. Next is the most important thing that is an shell command. Those shell is an interface which takes the inputs from the user and sends the instruction to the kernel and also takes the output from the kernel and sends the result back to the output shell. So it interacts with the user and the hardware between the shell application. So the application is these are the utilities program which runs on the shell. This can be any type of application such as web browser, multimedia and the text editor. So this was an architecture of an Linux system. So now we'll see the basic features of an Linux operating system. So why it has become so famous? It has due to the multi user capability. Multiple users can access the same resource like memory, hard disk, but they have to use the different terminals to operate multitasking. Next, the more than one function can be performed simultaneously by dividing the CPU time. Next is the portability. Portability does not mean that it is a smaller in file size or it can be carried in the pendrive or the memory card. It means it supports the different types of hardware security. One of the most important thing of a Linux OS is what it provides the higher security than any other operating system in the world. It provides the security in the three ways namely authenticating by assigning the password and the login ID authorization by assigning the permission to read, write and execute and encryption converts the file into the unreadable format. Next is a graphical user interface that is X window stream. Linux is a command line based OS, but it can be converted to a GUI based on the installing package application support. It has its own software reserve repository from where the user can download and install the many applications. Next, the file system provides hierarchical file system in which the files and the directories are arranged. Most important next and the one of the last thing of feature is open source. Linux code is freely available to all and is the community based on the development project. So, these were the basic features of a Linux operating system. Now, actually we are going to see the interface of a Linux OS that is an Ubuntu. So, this is the terminal in which you are going to execute all the commands. So, it provides the security means we have to authenticate that who the system is going to be used that is the assigning the password and the login ID authorization the permission to read, write and the execute and next is to file to convert that is known as an encryption. So, one by one we will see that how we are going to execute the command the basic commands using in terminal. So, basically this is the root at Ubuntu means the user is root here. Suppose if you want to make it a normal user then first will be an different user will be locked in. So, next will be the root. So, root is what you are going to type super user and you have to type the password for that. So, to set the password also we have to set the sudo p a w d. So, enter new unix password that is we are going to put some password for that. So, password is updated now you can log in as an super user already I have logged in as an root here. So, in which directories you are there. So, to see that there is one more command to see that p w d. So, by say so we can understand that you are in home root one desktop. Now, to see how many files or the directories are there on the desktop to list all the files. So, we have the command l s. So, l s means what we are going to have the Rahul is the directory v a is the p p t. So, these are the two files available on the desktop here. So, if you want to change the directory of a Linux. So, how we are going to change it is same like an MS draws applications like the cmd command. So, change directory. So, you can change you have come out of the you have come out from the desktop. So, if you do an l s now. So, there is no other here. So, we have to change go to home no such file or directory there is no such file here. So, these are the basic commands you have to remember how to set the password then you are going to have the p w d where you are going to locate this if you want to change the directory you can change it. So, we will see more basic commands in the coming lectures here. So, these are the my references these are thank you.