Linux Tutorial for Beginners | What is Linux | Linux Administration Tutorial | Intellipaat

greater than or

hey guys welcome to this session by Intellipaat currently the Linux kernel has 20 million lines of code and this is the smallest it has ever been and Linux is one of the biggest open-source projects in the world and you would have come across this programming language quite often which is the C programming language and 95% of Linux is written using C also guys before moving on with this session please subscribe to our website so that you don’t miss our upcoming articles now let’s take a quick glance at the agenda to start off with will learn what is Linux and about its kernel after that we’ll look at the basic Linux commands moving on we’ll look into files editors and file permissions after that we’ll look at shell scripting and also looping and conditional statements moving on we’ll look at more advanced Linux commands and finally we look into networking in Linux also guys if you want to do an end-to-end certification training on Linux Intellipaat provides a complete Linux certification training and those details are available in the description now without any further delays let us begin with this session so first let’s get started with introduction to Linux Linux is a uniqe like operating system developed by Linus Torvalds and thousands of open-source contributors so what does unix-like operating system mean so there was this UNIX operating system even before Linux was existing after that Linus Torvalds came up with an idea of creating a open-source distribution of Unix which is now called as Linux but right now Linux is more popular than Unix but the base of any Linux operating system is Unix because it follows the same architecture of shell and kernel and other applications so now Linus Torvalds is the main contributor for this large open source project Linux but there are other contributor contributors as well the Linus Torvalds started of this project but later on ask this is an open source project anyone could contribute to it so like that there were eleven thousand four hundred and thirteen different changes by individual contributors so this was after version 2.6 before that still there were a lot of contributions after that there were again a large number of contributions even from companies like Red Hat Red Hat is one of the most popular Linux distribution company so Linux operating system distribution company they have both community versions and they have paid versions so Intel is their normal is their IBM is their there are a lot of companies and they’ve all made contributions to the kernel moving on so Linux is an operating system it is reliable and secure than other operating systems also it is completely open source so open source in the sense you can take the basic Linux operating system and create your own operating system out of it repeat so so it is completely open source this basically means you can take the base of a Linux operating system lets operating system structure and create your own operating system using that so it was launched by Lannister walls in the year 1991 on 17th September so it is reliable insecure than others this comparison we’ll do right now because right now I am using and Windows operating system to explain you this particular presentation so the most common usage of any operating system is obviously Windows because it comes in built in a lot of laptops a lot of PCs and a lot of CPUs because Windows is the most popular the most easier operating system and also it has a name for it for personal computers because you can play a lot of games in that Linux is not that much compatible with games but coming to the IT sector coming to the development part Linux is preferred than windows ok guys a quick info if you want to do an end-to-end Linux training Intellipaat provides a complete Linux certification training and those details are available in the description so one more reason for learning Linux is Linux is everywhere so any operating system you take will have some kind of a Linux system within that so even in Windows you have command prompt in Mac OS again you have terminal even in other Linux GUI is currently like Cent OS , Cent OS Red Hat GUI then there is Ubantu gui GUI I in all of those graphical user interfaces still you have terminal emulators so normally the Linux system might be an command line interface but right now you have GUI based Linux operating systems as well but currently you might have a phone in your hand you might be reading this article in your phone or your phone might be on your table but every one of your family member right now will have a smartphone maybe not but right now any smartphone which is running Android on it has Linux running on it because the Android operating system is built using Linux principles it’s built on Linux the Android sorry the Android operating system is basically Linux and you can see 85% of all our phones or based on Linux that means there are iPhones there are windows operating system phones there are other operating systems which are again a subset of Android which comes under Linux and this is one of the reason second reason is your car uses Linux especially self-driving cars not just self-driving cars there are cars with inbuilt interfaces which have multiple operations you can basically click on a button and the window wiper will start so these structures certainly these algorithms or these these microcontroller systems are again running in Linux even self-driving cars need Linux to run them so why because Linux is faster it’s secure it’s reliable than other operating systems and one more again refrigerators also have Linux running in them so cook em so coming to why Linux is so popular and you can I would have told you cars using Linux your smartphones or on Linux even your refrigerators use Linux there are so many other possibilities your micro microwave ovens and there are so many devices which might be using Linux so now let us look at the supercomputers so you might be thinking okay so they’re on Linux but why not Windows why shouldn’t I keep Windows and use the Windows operating system to do all that so here comes the fact so you can see here that sorry so you can see here before 2003 or 2004 UNIX was dominating the supercomputer market and even there was some bsd there was some Mac operating systems there was some Windows operating systems running on supercomputers but right now in 2020 the top 500 supercomputers existing in the world are running on Linux operating system you can see the entire market is right now captured by Linux so why all supercomputers need Linux is because Linux is lightweight Linux is fast Linux is secure Linux is reliable so coming to the fact so if supercomputers are running Linux and they are successful using Linux why not your PC why not your desktop so basically it’s not a bad practice to use all other operating systems but coming to the development part Linux is more preferred by developers it’s not my personal opinion but Linux is more preferred by developers but if you’re building an application on the.net framework obviously you need Windows or you can emulate it on Linux operating system as well you can learn run of Windows virtual machine or Linux so choosing an operating system is you wish it’s for what kind of a need you need that operating system but right now we have come to learn Linux let us look at more more data about this Linux so right now let’s compare between Windows and Linux so this is one of the main questions asked what is the difference between Windows and Linux so this you should understand very well first Windows Server you need to purchase the license windows is not free windows is not open source if you’re running Windows so if I’m running Windows currently my windows should be licensed my Windows is licensed if it is not licensed that means you’re it’s a pirated version of that operating system next Linux is free it is open-source operating system there are paid operating systems as well in Linux but so cent OS is free Ubuntu is free so you can download them and install them for free and then not many customization options because like Windows releases few operating systems in few years like let’s say right now we have Windows 10 maybe in a couple of years or the next year we might get a Windows 11 or 12 but you cannot customize it a lot but in Linux there are so many different distributions even let’s say Ubuntu there are so many different versions in Ubuntu then there is sent OS then there is Federer that we’ll look at later we look at the various distributions but this is what is available there are so many Linux distributions and you can choose one according to your needs and then Windows is vulnerable to viruses and malware threats a powerful antivirus software is a need so in Windows without an anti-virus software if you are trying to download something from the internet I’m pretty sure you will catch up a malware in your system because Windows operating system is quite weak in the security aspect it still has Windows Defender but still Windows Defender is not equal to a full-time dedicated antivirus software which basically reades all the time for malwares it detects and tries to delete it so that’s why Windows is a no-no for downloading things without antivirus but in basically in Linux it’s more secure than Windows and the kernel is built as such viruses cannot be easily broken so for an hacker to create a code which will break the Linux system it takes a lot of practice the code should be very efficient so that it breaks the Linux system so these are the differences between Windows and Linux and before Windows was ms-dos which was again a command-line interface and then there’s Linux again it was a command-line interface but then later on or operating systems got evolved windows got its GUI now right now Linux also has its GUI there are various types of GUI’s so now let us look at the different Linux distributions you can go for coming here then you can see Debian you can see fedora you can see Ubantu can see Cent OS you can see the Red Hat and you can see SUSE so there are still a lot of Linux distributions but I’m just putting up some popular distributions you debian fedora Ubuntu and all so CentOS is the operating system which you are going to use throughout this Linux course so will not be using any other operating systems will be using CentOS CentOS is basically the community version of the Red Hat on price Linux and cent OS has all the features of any other Linux distribution there is also Kali Linux there is there is so many varieties there are so many distributions and relax so you will have to go ahead and check for what exact purpose is this particular distribution better for and choose your Linux distribution accordingly but most probably accept the package managers the commands the Linux basically Linux commands the basic Unix commands are going to be the same in every single Linux distribution so that it’s pretty easy to move from one distribution to another so basically if I am currently working on CentOS i can easily adapt to Ubantu so it’s like that so this is the introduction to Linux okay guys a quick info if you want to do an end-to-end Linux training Intellipaat provides a complete Linux certification training and those details are available in the description basics of shell now let us get into it so first we’ll be looking at the Linux architecture so the Linux architecture in the sense it is not an architecture which is built using hardware so the hardware part is what you mean by the laptops hardware or the CPU so that is the middle part over here hardware so hardware’s just cannot contact with the users directly so let’s say if you just have a motherboard laying on your table you cannot communicate with it a motherboard or an microprocessor or anything a complete set up is there and you cannot basically you cannot communicate with it because there is no common language between you and that CPU so to enable that there comes kernel which is the middleman which basically contacts the hardware for us so we are the users we try to utilize few utilities or few applications so let’s consider the application is a calculator so the calculator as using the calculator you want to do arithmetic operations so now let’s say this is the calculator you are trying to use that application so now the calculator will basically this application so there are a few commands within D so there are some commands within the Linux and those commands are executed on an entity called the shell so we will see what is shell but right now let’s consider the architecture so you have the applications and you have this shell after that shell basically execute your commands for you it will basically communicate with the colonel for you so as an end-user you see the shell you type in a command or you type in something or you just click on an application the first instruction will be given to the shell so the shell gets it so let’s say you want to copy a file so you use the copy command so shell knows that you’re using a copy command you’re trying to copy a file to another file so now this instructs the shell instructs the Kernel basically it interprets the command and it instructs the colonel to do this particular operation so colonel will understand what exactly is the operation and it will push that to the hardware which in a language switch the hardware can understand so an assembly language or something like that or a microcontroller language so it sends it to the hardware so the hardware will do the operations for you send it back to the shell which where you can view that so as a user you just know you’ve typed in the command but you do not know what happens inside and what comes back so you type in a copy command and you get the results in fraction of a second and you don’t see what exactly happens behind so you only see the monitor where you type in the command you are typing the command on the shell which is an interpreter for the colonel so the colonel gets the command and knows what to do and it does those operations with the help of hardware and then sends it back to the colonel and which is this will on your shell which you can see I understand that the operation has successfully happened or if there is an error you can see the error too so this is the Linux architecture so moving on freely first I have to understand what is shell so I shall interprets the commands you have entered using a keyboard and sends it to the operating system to perform them so as we have discussed the Linux architecture you have the shell and then you have the kernel so both these entities shell and kernel or programs which are running on the operating system the operating system is what making the shell and kernel possible so kernel is trying to communicate with the hardware shell is the interface between the kernel and the user so now what shell does is it interprets the commands which as a user you give into the system using the keyboard or the mouse so shell interprets that it understands what you’re trying to say and it translates it and sends it to the operating system operating system in the sense the kernel so it sends it to the kernel kernel now understands what exactly should be happened it uses the hardware help to complete those operations and once it is done it sends it back the shell so that you can view it on your monitor so the basic explanation of shell is this you need to understand this only then you can go ahead with your Linux training so we’ve understood what exactly is shell moving ahead so nowadays yeah there is a lot of graphical user interface based to the next systems so even st.
at the various
OS is a graphical user interface based system there is also CentOS server which is a command-line interface but there is also a graphical user interface so like Cent OS there’s Ubuntu there is Red Hat there is Debian and there is Kali Linux there is a lot of Linux distributions which have GUI s– so in a graphical operating system how can you basically communicate with the kernel with the use of a shell so to emulate the purpose of a server to emulate the purpose of the command-line interface all the GUI based Linux distributions have a terminal within them a terminal is basically an emulator or a duplicate of a command-line interface so if you click on the terminal I think most of you would have seen this at least once if you open the terminal in your GUI base to the next system you will see a terminal like this so there you will have your username at localhost or any name any of your systems name can be given here and then you have this dollar symbol and here you will have to enter your commands still you can see I have entered the command called PWD which means present working directory this explains the present working directory and currently the directory is slash home slash intellipaat so it’s in the directory Intellipaat so that’s what you’re explaining over here so this is the emulated version of a command-line interface so you can see here a terminal which we see in the GUI server emulates a command-line interface in Linux server terminal emulators are were commonly used now due to GUI operating systems like Mac or Windows or Ubuntu so even in Windows they have a command prompt even in Mac we have a terminal even in Ubuntu or ascent we have a terminal which emulates or duplicates the purpose of a command-line interface server so now coming to table shells we saw what is a shell and how does the emulator official looks like in a GUI based system now we’ll be looking at the top shells in Linux so there is not just one Linux as I told you Linux is an open source system so obviously there are a lot of contributors who creates different types of shells so the most common the most so basically a default or shell you can say is bash that is life the name the elaboration of bash is born again shell is a default shell in a lot of Linux distributions so born again shell is the default one and even in CentOS and even in your went to in a lot of different Linux Distributions- is the default one you can further install other shells also it is your version and then there is Z hesed which is basically Z shell and it is similar to bash or an extended version of it so basically as I told you they take the Linux operating system and create another Linux operating system which has better features so like that they they took bash and made it better or added few features like sharing your command history across multiple terminals so let’s say there are four different users using the same Linux operating system within different user names so you can share your command history to another user so this is one of the features there are so many useful features in Z shell this is one of the useful features in V shell so that’s what I want to share with you so going ahead there is fish-friendly an interactive shell so it is again an extended version of the common shell which is bash so it has great features like auto completion of commands so fish is an amazing shell so fish has this ability to autocomplete your command so let’s say you’re typing in grep and command is going on going on so you don’t want you do not want type all of that so if there is a command grab if you just type gr and hit tab you will get it auto-completed so it is like intellisense so it is like an ide with intelligence so you can use fish for that and then tcsh then X seashell is an extended version of seashell so there is another shell basically see SH or the seashell basically the seashell is written mostly on the C programming language that is why it is called as seashell and tcsh is again an extender version of the Cecil they’ve taken Cecil and added more capabilities to it so the plus of tcsh it is scripting language because it will be similar for the users who already have experience in C programming so that’s the benefit of tcsh if you already have a good experience with c programming if you know how to write code in in c programming so then you will find shell scripting pretty easy in tcsh because it might have the same method of writing so that’s what they’re telling over here there are still so many shells you can just do a simple google surgeon getting over what more multiple shells but these are the top shells and this is the most popular shell so that’s why i’m explaining them here so going ahead so that’s this is the command which i executed in the previous previous window which I explained you while explaining the GUI based terminals so a simple command to interact with the shell this command below provides the present working directory so I wanted to explain an example of how you interact with the shell so basically if you type in PWD and you are interacting with the shell when you hit Enter the shell understands that you are entering in in a command first it validates the command whether this particular command is valid in this Linux distribution PWD is the valid command then it further pushes it into kernel kernel gets it in and pushes basically execute the command with the help of the hardware provided and then it gives back the result of the shell and shell displace it to you so that you can view it so this is one of the example which I wanted to explain you the kernel okay so first a linux kernel is a unix-like operating system kernel so again as Linux is the unix-like operating system obviously the kernel of Linux will be a unix-like kernel so it is a computer program which is the core interface which connects the hardware components to the software processes so the software processes which you are trying to establish or trying to interpret as basically you are typing in the command on the shell and hitting Enter so you will know this part basically you will know the application part where you are typing in the command and then you do not know what happens in the back it just you get the result so what happens is whenever you type in a command you have the kernel in the middle a kernel is basically a very huge program very it’s a very huge program right now I think it’s standing up at two million lines of code so it is a very complicated program and so a kernel assets complicated it is also that helpful so a kernel is the main interconnection between the software application or the software processes on the hardware components so let’s say if you are trying to find out how much RAM your system is currently using so you cannot directly go and check the ram in your system you need a process running in the background which basically connects to the hardware components and checks how much ram is being used and sends that information back to you so that is what the kernel does so kernel does all kinds of operations that we’ll see now so the top operations performed by a kernel first resource management and then memory management and then device management and finally system calls okay now let us get a brief about each of those operations first Resource Management so kernel decides which process gets a resource for an operation so let’s say you are running multiple processes parallely saying that multiple processes two processes need the same resource for an operation so right now the kernel will decide which operation should use that resource first or which should you second because it should not end up in a deadlock situation so to avoid that Colonel performs an operation which basically chooses which exactly needs the resource right now or it may delay the process of execution so it might give it to a process which takes lesser time first and then it gives it to a process which takes a longer time so the resource management there are varieties but this is one of the main operations which the kernel does second one is memory management memory management is very important for any server for any computer even in your Windows system you have 1 TB of space and even then memory management is very important because memory management is taken care by your system your operating system windows and it takes care of it well so like that kernel takes care of memory management as well kernel has complete access to the system memory and must efficiently manage it and a lot of memory access to process so why do you need memory exactly is memory is not for storing content memory is to run processes efficiently and effectively so the kernel should know how much memory should be allocated to each processes so that your system is not completely taken away of free memory so let’s say you have 100 MB of memory and there are 10 processes your kernel should decide how much memory does each process deserve to use so it should provide that efficiently and the device management so device management it’s pretty common in every single operating system so basically if you are using a Windows system if you just enter the pen drive you will be seeing that in your my computer or this PC software so like that device management is also taken care by kernel so if we connect devices as a printer or a pen drive so the kernel will detect it and the system will establish connections with the peripherals so if I connect in a pendrive so this particular system my operating system should detect whether I have connected a pendrive or not but that’s not detect then there is no use of you USB port in your computer so the kernel will detect it and there is a separate directory in kernel which is known as /dev de B so that particular directory is especially maintained for device management so any device entering into this particular Linux operating system or any Linux operating system will have a separate directory for them in the divet so if I enter pen drive that pendrive will have a separate directory within that /dev directory so the next kernel also takes care of device management and finally system calls system calls this is one of the important concepts and this is an interface between a process and the operating system when the process does not have permissions to access a resource a system call provides it without the process accessing the resource directly so basically let’s say you are running a process but you’ve not given the processing of permissions to use a particular resource so you can use system calls for that process you can embed system calls in your shell script or in your code so that when that particular system call is used your process will be given access to that resource indirectly using system calls so that is the purpose of system calls itself to not stop the process from running it does not interrupt your execution it helps your execution to complete as fast as possible for that you can use system calls and also you can use system calls to basically do more operations on the operating system level so let’s say you want to abort a particular process immediately you can use a system call for that so there are various system calls are these are the four important operations performed by a kernel so we’ll be saying this later in this course so you have to just assume that kernel is the you don’t need to assume actually you’ll have to understand that kernel is the main component of any Linux distribution and kernel manages all of the top operations of a Linux distribution so right now I think we can get started with Linux itself so first we’ll be looking at some basic Linux commands so that we can get started with Linux easily so these are for understanding how exactly Linux works so first we look at some basic commands moving ahead okay so first we’ll look at these commands command and their tasks so PWD explains the present working directory who are my explains the user name date explains the date time and then so there are still more commands who make directory cat move so now let us start from the first PWD and try executing these so let me open so I have my virtual machine opened so I opened it but once it’s open we can start off with the process I’ll open terminal terminal as I told you terminals are emulating shells they’re emulators of shells where you can type in commands and it works like a command-line interface so so let’s get started with that once it comes yeah so now I’ll open terminal yes I’ll just click here ok so since it’s running and yeah so first was PWD if I type this in you can see slash home slash in telepath so you can see that over here so this is my present working directory so under Intel apart right now I’m working so that’s why I just explaining it as the present working directory so let’s say I go back and now if I do a PWD it explains home because I am in the home directory so that’s how this works that’s how PWD works and it’s one of the important comments you’ll have to remember it’s pretty simple so let’s say you have navigated into multiple directories you exactly do not know there so you can just do a PWD and check that for yourself now next one is Who am I so Who am I is again a simple command but it explains you which in user name have you used to log in so let’s say you have PI different users now you can basically you can log into this particular central system from multiple users as multiple users so if you might have forward which user you are using as you can just type in this command and it will give you the user name and then and then there is date history so again I’m going to type in date it explains you the date Friday January 31 and it explains the time and it explains a year ok so we have seen that so this is eastern side of time so that’s what it’s explaining so next we have history we’ll see history later then we have copy the abloom ooh we have clear man exit and cat move alias echo LS so echo will see later LS will see later because we will do these commands in detail we learn about these commands in detail right now I’ll just start off with the basic commands so first so let me clear this so right now you have cleared it and you don’t know you want to see what and all commands you have used still so that you can take out the command and use it again so for that you have this command called history which type in history you can see all the commands which you have executed previously so you have history clear date Who am I and PWD play WT and these were previously entered so it also explains the previous history so this is why you need this tree if you would have forward any command you can just type in history and copy that and paste it within this and so let’s say I have forward in this so I will just copy this and paste it over here so this is what history and then one more thing is touch touch and one dot txt so the file got created but it won’t open so you can see the file got created over there so now there are various text editors we learn about text editors as well so right now I’ll just open it Nano dot txt and hello world to save it is ctrl o enter ctrl X so I’ve saved the file and the file is ready right now so let’s say I want to see the contents of the file without opening the file so how can you do that so it’s pretty simple you can use the command cat CID and type in the file name so cat one dot txt and you can see the typed in the files contents over here so this is why you can use cat and another thing so let me create another file – dot txt and right now you have a one dot txt Anna – raagh txt file so you want to copy the contents of one dot txt – 2 dot txt you use a copy command which is CP then source and destination so once they’ve entered so now if I do a cat or 2 dot txt you can see hello world inside that I do not open those files I just use the command CP which copied the contents of the first file into the second file so you can use this also you can do one more thing that is move 1 dot txt – p dot txt so right now there is a 3 dot txt file but there is no 1 dot txt file because I moved the contents of one dot txt as well as the file I moved it into 3 dot txt so right now if I do a cat of the file 3 dot txt you will see the same content inside that again I can move it back by use in this command so this is the move command you can basically move pile within a directory or you can also move a file outside of a directory so let’s say move one dot txt slash home slash one dot txt so I want to move it to a file which is not in this directory so it’s explaining permission denied cannot move so let me add a pseudo in front and check so I’ve given the permission so now you can see here the one dot X T file is not there going back so I’m in the home they retreat and here you can see the one dot txt file and if I do a cat it should have the same content because I just moved the file here I did not just move the file also I move to your contents of that file so guys we’ve seen the basic Linux commands which are needed to start with Linux any Linux distribution those commands are the same so right now we are going to see another command which is called echo and it was one of the most important commands which you have to know so moving ahead so first what exactly is echo echo is used to display a line of text or string by passing it as an argument so now you can see this example over here echo in telepath it basically printed that over here so again you can see over here echo so sorry for that again you can see over here echo display text display line of text so this is what it does this plays a line of text and there are some descriptions trailing newline or so these are some examples which will be doing so right now we just remember this it is basically a command to display a line of text restraint so now there are some options you can use these options while using echo so echo and if you use a minus n it gives you the output without a newline it adds that particular oh sorry it adds that particular option to the same line itself so first let me clear this just a second an option two so I’ll just make it huge so that it’s clearly visible okay so right now I assumed it so guys I wanted to say I Pro so echo hello so you can see it has printed hello so echo hello it can also sprint a complete line and then so you if you do this hello – so as you told you it will not use a new line it prints with the command line itself so this is one option of echo then another option is – e this will allow usage of back backslash escapes so there are some backslash escapes or there is B there’s n t b so b removes the space between text and n prints the text in a new line then that’s a horizontal tab does a vertical tab so let us execute these one by one so first let me do this so if I type hello / I’m using / B so I don’t want space between these two lines but if I do this it won’t work because /b is not escaped over here coming back here and also I have targeted and wrong so even though if I have typed in the slash correctly so again you can see the slash is not there but B has been added so to escape this you can use the option – e hello world so think I’m doing another mistake so the thing is I think we’ll try with codes yeah so that’s what /b basically again I did not put in quotes so it thought that that is again a part of the string itself so right now I’ve used – E to escape the particular option that is backslash B so now hello world in between that I used slash B and it removed the space between hello world now one more thing is – /n / end separates the words and prints them in separate lines so let’s say hello world how are you so you can see that hello world how are you so hello is in one line and after that I have a newline world how is in one line then after that I have a new line then are you so this is one and then you have two most commonly used ones which are / H + / each so / t does a basically a horizontal tab / you can see here / t that’s a horizontal tab / b does a vertical tab so going here / v and now you can see that horizontal tab it left in eight spaces or a tab between hello I am void and horizontal vertical tab is basically a new line but it will be on the same line but it will be a line different so let’s see them with both and now now these are slash tees now let’s see both of them with slash B’s and now you can see the difference so here when we did hello world are you here we used a slash t and here we use the slash way but right now I am using in both the places and using slash me basically they’ll be in the same position as the same line but they will be a line apart so this is how you use these options so now I’ve also added some examples over here the same kind of examples how are you and /v / t / b all these examples and one more thing i want to do is explain is you can do this with echo so now X I’m putting in a variable and I’m just giving it some random number so now if I do a dollar X you can print the variable so this is one of the most useful things about echo I’m going back and you can do one more thing like if you do an LS you see all the subdirectories of that particular tree you can also do that with echo thar so you can see them but they will not be displayed in a colorful manner LS actually differentiates between directories and files but echo cannot do that it just prints what are the contents of that particular directory going back what are the examples yeah there is one more example for expression so let’s say I have already entered the value for x Acme enter a value for y yeah so no echo dollar this is the format so now X and plus try this if it works then it’s fine yeah so it’s 79 so it has added 23 and 56 so the problem is if you do this dollar x plus dollar Y it will not print it it just prints the content of X separately and Y separately but to do an arithmetic operation you will have to put dollar friend and to paranthesis and in between you will have to write in the our thematic competition so let’s say you want to subtract them then you can go ahead and do it like this so this is how you use the echo command and these are the basic examples of it so we’ve done the hands-on for echo command so we’ve seen echo and other basic Linux commands now we are going to see set and unset so set again is a command but there are various types of doing it there are various commands to set a variable and there is this unset command so if you have set already a variable as a global variable or the local variable you can use the unset command to remove that so now let’s get started first we learn what is set and unset so first the set command is a built-in function in bash and few other cells which you can use to define the values of system variables set it’s not required to set a variable there are various ways to do it so as I told you set is the command so in the back end that is the command which will run so I did X is equal to a number in the last session or doing an echo of it so when I did that it automatically took it as a variable so that particular operation is a set operation set need not to be a command to be used but that is the operation which happens whenever you are trying to give a variable value so you cannot use the command export to create environment variables so while you create environment variables you are using the command export basically again that is a set operation export is another command to set environment variables even though setting environment variables and variables are similar the only differences environment variables are for the complete system globally it is available but normally setting a variable like X is equal to 23 or local or locally available there local variables and finally the unset command the answered command is a built-in function in bash which you can use to remove a variable which is set so if you already set a variable using export then you can use the unset command to remove them for going ahead we will see some options the first option is – be notify of job domination immediately second one is – e exit immediately for command exits with a non zero status then third one is job control will be enabled and fourth option is pretty good so all export these are they stay other options you can see these options over here you can use this set command to turn off or on particular functions so all export in the sense if you are not enabled this then you cannot use the export command if you have enabled this then you can use the export and so we’ll see some examples first though you can see hello one echo hello this is what we did in the last session so this is done this is for local variable and this again the same thing this is a global variable and yeah it could all Hollow one echo dollar X unset hello echo dollar hello dollar X it’s only printing the value of x not hello because we removed that variable and then again here hello one export hello we have made hello into a global variable echo hollow is explaining again we are entering another bash I under the bash we are trying to do that but again we are getting the value but in this particular example you can see we entered another shell but under that shell you cannot see the value of hello because it’s a local variable when you use export it becomes a global variable so now this is one way of making a variable global and there is another way which is export X is equal to two instead of providing hello equal to one then export hello you just put expert hello equal to one so that will be more than enough and then you can see this set plus oh this is where set command comes in so you can basically stop or dot particular operations in your system so if you have installed so there is a particular text editor called Emacs it might not be installed in the fall you can install it later so even though if you have installed it you can basically use it if it is – OH that means you cannot launch eMac if it is plus / then you can launch Emacs so you can use the set command to stop and start particular operations so that’s one of the useful examples so you can see to do that set – oh all export if I do a set plus o it explains all the set operations over here and you can see that it explains all export has become – OH that means I cannot use the export and here it’s + o okay so we’ve seen that now let’s go and do the same commands in the operating system so if we open it I will enter the wrong password now I’ve entered it right ok so right now guys let’s do some operations so we did this hello key so let me use X itself so X equal to 45 so let me echo this so it’s explaining the value now if you end a bash because as I told you incent OS the default shell is bash and if I use bash so now I’m inside another shell so you can see that if I do an LS it’s explaining the content but if I do an echo it does not explain the value so basically if this particular shell does not have the value for x so here I can so let’s say I’m giving 76 and different doing an echo of X so it explains 76 but you might think won’t this overwrite the value of my already created X variable so to exit a bash shell it’s basically exit for any shell else exit so if I do an exit it comes out so now again if I do an echo of my I mean now it’s again explains 45 why it explains 45 because that particular X is equal to 76 or have set the variable X as 76 in the bash which I launched recently but the variable X which was already available which I already said had the value as 45 so I do not make my X variable global when I first created it again I did not make it global when I again created it inside the another shell so that each shells have their own values for X right now because they are local so now how to make it do good so it’s pretty simple I already have a variable called X so what I’m going to do is I’m going to use this command export export X right now sorry I don’t know why I did LS but X for X right now it made my X variable as global so right now I’ll do a dollar x over here so you can see that my dollar X is 45 here now let me do bash and try it over here and again it explains 45 because I’ve made my X variable global it over red so basically I made my X variable global this made this particular variables value the same in every single shell so you can launch another shell over here but still the value of x will remain the same because it is now a global variable with the same value throughout the entire system now I’m clearing it sorry I’m exiting it so this is how we use export one more way of using export is like this export y equal to 67 so now this would have already become a global variable so other examples I wanted to explain are I’ve explainn those three examples and then yeah I wanted to explain set command so I’ll clear this now set just I will enter set then you can see every single function you can see every single variable which is set over here so you can see columns 127 you can see every single value set over here mail you can see the mails directory you can see you can see the old PW this was the last time I used PW and the last time when I use PW this was it so now let’s try this once again let’s do a new Peter WD and now let me type in the set command now let’s go up and check the old PWD so now the oh the value of old PWD should have been changed to the newly entered value of newly entered value which is a Center going up you know I came to the top so things over here login that should be here movies for columns final lists and then there is no home home variable login name is in telepods home and not able to find old yeah it’s over here again it’s the previous one not able to find variable okay so that’s fine so set another option of setters so one more thing I want to explain is so you can see this so this was one of the important commands you should know so let’s say you’ve done let’s say alias and not alias or so you can see update a exclamation and I typed in just PW so it already recognized PW means PWD and it explains the later execution of it so let’s see easy just let go so it explains the execution of it so if you have typed in a command which you don’t want to type in completely again or you don’t want to search it in history and again type it you can basically put xsplit exclamation and type in the first two letters of your command and it will detect and explain you the latest results of it so this is one of the things then coming to set set let me type in oh sorry set plus oh and now you can see all the operations over here so set plus keyboards at minus zero monitor set plus notify and all all of these so basically you can I can do a set minus 0 and all export so now if I do another so now you can see it would have been changed to – oh so this particular option stopped this so let me try so to understand this better the set command so let’s do this so there is history over here so let me type in history and it explains the complete history with the history command so let us try this – oh sorry plus history so now let those two a plus Oh so I think now it would have changed history where is it history is plus oh let’s try history once again so it’s explaining the complete set of everything so now let us stop it once again so basically it disables but it does not stop it from working so again you can see history the latest one so this is so no coming back to set I think to understand said you can check the manual page so if you open it it’s not explaining the exact command but it’s explaining some other things so you can see Bosch echo enable eval execute like say it’s explaining all of the commands in this particular batch but it’s not considering set let me quit this now let us do a man for export what exactly is exported so again it’s not explaining that it is a default command so now we’ve seen the export command and how to set a variable now let us see how to unset it it’s pretty simple so now echo dollar so it has a variable then use the command unset and this type in X so now let me run this again so right now you don’t have a variable so this particular variable X does not have a value so now I have unset that variable so this is how you set it up and there is one more command env so env is for setting environment variables so if you type in env you can see the complete environment variables and you can see that user name is in telepath and then you can see the user is in three polygons and photos so I wanted to explain something really relatable so that’s why I wanted to explain this and then there is the shell because as I told you the default shell here is bin Bash it is bash actually so the location of Bash is underpinned so that’s why it is explaining the shell over here so this explains the environment variables the set command basically explains the complete variables inside this virtual machine or this particular operating system so the set command explains the entire variables of this complete operating system but env just explains the environment variables of this particular operating system so we have seen these commands so the next command is expr or expression so let’s see the basic definition of it so the command expr computes a given expression and displays the output so the exp our command is used to calculate an arithmetic expression which we have provided and it gives the output of it so the below command which is exp are – – version explains whether we experice installed in your system or not normally it will be already installed in your system while installing any Linux distribution because the experience one of the most common commands so check it if you want to and if it is not installed then you can install it normally and then I checked this in the man page so these are the operations which exp R is capable of there are still more operations but these are the most common operations so you can see argument 1 and then argument – then R so basically argument 1 slash is basically our operation and you can see if it is either null or null not zero other ways argument too so it explains argument 1 if it is neither null or zero if argument 1 is nothing or if it is 0 then it considers argument 1 it cannot really go to argument 2 and then this is a non command and then argument 1 less than or argument – if argument 1 is lesser than argument 2 it will give a number 1 if not we’ll deliver a number 0 so these are some again some logical operations then coming to arithmetic operations plus minus you can see I added Matic some arithmetic difference product quotient and remainder so moving ahead and these are some examples so first you can see an addition second you can see a subtraction then multiplication division and you can see exp or length as well you can check the length of a string then you can see some logical operations which I did in the right side so let us do these in the shell so let’s start off with it so expr let me do the first command so I’m going to check whether the experienced all so yeah it does install it should be installed so now exp r1 plus 2 so there should be a space in between only then it works so yes otherwise it considers it has a single argument so exp r1 plus 2 it gives me this then 1 minus 2 gives me this 4 but one more thing you have to consider this while doing an operation like multiplication or subtraction you should add the backslash in front of it so let’s say backslash star I’m going to multiply 1 and 2 so only if you add a star in front of it gives that so let me change this so now you can see it’s 8 so only if you give a backslash it will work if you don’t do a backslash it will not work because the argument is wrong so now I will do yeah so this is division and then you can see the coefficient 0 because it devices perfectly so I’ll just give a random number and you random number here so it’s 16 so you can see the quotient also is explainn and you can also divide them it can be any big number so it will not explain the decimal point over here so it will explain you a perfect number so then we will do some logical operations expr 10 equals 10 so it is equal to then it gives 1 if it is not it so if it is not it gives 0 then we can see the or operation also alright one more thing I wanted to explain is 10 less than 11 okay sorry I forgot the backslash so now you can see it’s 1 so you can see it’s 10 so let me make it small again it’s 10 so now if I make it 0 now you can see it’s 23 it’s this is what this operation does and then there is greater than and then there is sorry there was greater than then there’s greater than or equal to and so you can see this is how you can use expr there is one more thing about expr is that you there are some certain so let me check the main page there are some certain operations which you can do using the X they are so this is where I got the list of what are the operations it does you can also you run some regular expressions in that after giving valuable names variable names so here you can see the length and strength so you can calculate the length of a particular strength so now let me give a string is equal to hello so now at exp odd length a so it explains the length of a now I’ll do a dollar and print of it now it explains the length has 5 so when I gave a just calculated the length of a when I gave dollar a calculated the length of the string which the variable a has so this is these are the basic commands which you have to remember while working with Linux so now add a file of shell script using Java so the name of the header file header part of a shell script is called shebang which the hash and exclamation marks together so this is one of the most important things you have to know before starting off with Linux because in Linux you do shell scripting so for shell scripting this is one of the important things you’ll have to understand so first hashtag and exclamation together so this represents which interpreter or script should be interpreted with so using this shebang header you can mention what is the interpreter so normally in this particular operating system which is sent OS 8 so here bash is this shell so you can just type in hash exclamation slash bin slash bash and then start typing your shell script so that when you run the shell script the shell will automatically understand this should be run in bash or if you put hash exclamation slash bash slash CSH if you type in a different shell if the shell is installed in your particular machine then it will use that shell to execute your shell script so this is how it works so the last one is bin slash bash is this not provider if it it often considers bin slash as such so as such is the most basic format so normally if you do not provide the header file for a shell script it automatically considers it has a normal shell script and it uses the default shell and it uses that to execute that shell script when you put that particular shell script shebang header so hash exclamation slash bin slash bash in your script so that particular kernel will understand that it should be executed in bash and it will be executed so this is the use of shebang and coming down so this is a small script or a small shell script so you can see the use of the shebang over there it understands it is bash and echo this is a sample script SH using SH or using bash there are various ways to run a particular script file I’ll explain that so this is the sample speed okay so this is a sample script let us go to our system and run it all so okay so first you will have to create a file I’m going to create a file Nano let me just type in 1 dot sh I’ve opened the file so hash exclamation slash bin slash bash echo hello all so this is going to my script fight I’m saving it I’ve saved it so the first way of exiting this is using as such second way is using – third way is pretty simple dot slash so for this you will have to be the root user against another command not font so that is the basic way of doing it or you can do on one more thing so let me do another file create another files so I’m going to type and just echo hello and saving it so now there is a wonder research and research file so if I do this it’s explaining hello even though I did not enter a shebang file because it is stored in a format called dot SH and also I am running it using SH so basically it assumes it as a shell file and it uses the shell to interpret it so you don’t need to always mention the shebang header file but when there is Sidney when there’s when it is a huge shell script then I suggest you to insert it so that your particular shell script is considered as a shell script because you might copy the shell script and use it in some other shell and at that time without the shell header it will not know that it is a shell file so that’s why you’ll have to use that so we look at various text editors the first we’ll look at them there were some of the most commonly used text editors on one of the most popular text editors so vim is actually lightweight and there are a lot of benefits we’ll look at that later so then there’s one of the most popular text editors then Emacs and then GNU Nano so I quite often use Nano I don’t use them that much I like Nano better than them and there is G edit so even G edit is a quite popular text editor which is basically G white text editor BIM in Nano or the command line text editors where you can type in the terminal itself so now looking at these we look at the most popular text editors them and Emacs are the most popular text editors use so this is basically based on personal opinion you might prefer a particular text editor for its usability so I use now because it’s pretty easy to create save and close the files and it’s pretty easy to type in files also so in them again you’ll have to look at the functionality you will have to work with it if you are fine with it then you can go ahead with them if not you can try Emacs as well so these are the two most popular text editors now this is how them will look so them basically is a command line tool as it told you and you can see that it just opens a window whether it is the command in the command line itself and it explains something so first to start off typing you have to enter I which is insert then you can start typing and then coming to Emacs you will have to install Emacs and I need to when you open Emacs it will be open the as an application so Emacs it’s not a command-line tool it is an application so again these two are the most popular but still people use Nano G edit and still there are a lot of text editors they be use all of these text editors – if it is comfortable for them so next we look at some things about them so them stands for an improvised version of the VI text editor so basically them is V I improved that’s it so VI improved a slim it’s the improvised version of the VI text editor which was commonly available in a lot of not even in a lot of in or every Linux distribution which is available so right now why is film popular so first it’s light right it’s easy to open it’s easy to work with it and it does not take a lot of space second it’s very easy to open an identify as I told you third if you boot on that system will miss most possibly installed that’s what I was telling you because women’s one of the most common text editors so that in most of the Linux distributions so even we installed CentOS I’m pretty sure incentivize them will all be be installed so in most of the Linux distributions women will already be installed in it so that you don’t need to go ahead and install it once again and start using it so that’s why we miss popular so moving ahead these are the BIM modes first is the command mode in the command mode you will not be able to type but you’ll be able to enter commands so you can see you we can enter commands for copy paste delete or replace and then in the insert mode once you press I in the command mode you your command mode will be shifted to insert mode then you can start typing in and then once it’s done you can just press the Escape key which will come out of the insert mode and then command line mode this is also a command mode so again this is command mode but every command you provide should start with a colon so to quit its : q to save and quit its : WQ so this is what happens and fourth is visual mode visually like text and run commands on selected sections to shift from command to which will type you allow to press V so once you press me you can visually select and edit things like that so these are the four different bi m modes then modes so you’ll have to remember this so now let’s create a file so just first let us look at the peabody then go ahead to our the next machine and start working with it so i’ve created a file and pressed i and entered some text as hello world and then just escaped and you can see in the bottom corner : WQ and hit enter so the file would have got saved so these are some options inside the boom command mode is for inserting capital OS insert text on the previous line small OS in the insert text on the next line ie sup in text after the cursor capital a is up in text at the end of the line so these are some options there are still many many options you can see here creating and saving a file so first let us go to the in the next machine so this is my machine so I opened it next I’ll have to open the terminal and first I’ll make this bigger yes so right now if I type in them so you can see Wilma is already installed in my system then P I am through so that solid explaining them is already installed so now I get back so : q I got that so Emacs the thing new Macs will not be installed Emacs is not installed and then nano so Nano is installed and I mostly preferred Nano because it’s pretty easy for me because mostly I’m not going to edit anything I’ll be typing in and then I’ll save it and close it off so now it’s pretty simple it’s just three different controls we’ll have to remember to navigate them ISM has a lot of commands a lot of different modes you’ll have to remember all that to work with it so first please create a file with web so to create a file with name first enter them and then enter the file name so let’s say one dot txt so I have created the file but so now I will not be able to so now you can see I am able to type in but you can see there is nothing over here so I’m going to press I and you can see the insert word over there so this means I’m in the insert mode so endangered mode I will be able to type so once I hit escape now I’ll not be able to die I’ll be given here so if I hit Q what happened what will happen is it will just quit it won’t save the file but if I hit W it basically means to write and quit it will save and then quit so done so now if you open the file once again now you can see it is created and saved now let’s hit V now it’s visual mode so in visual mode again you should learn some things and see I’m selecting everything and I’m able to change it accordingly so basically visual mode is to select so let’s say select a particular text or select a particular line and then use that line on that line you can change it but in insert mode basically you cannot do that in insert mode so you can see I’m trying to do that exact same thing so you cannot do that but in visual mode you can do that so you can see I can do that in visual mode but not in insert mode so now I’m saving it once again so if I do work that out quando txt so this is the latest save once so going back to so we’ve done the first part we saw or the various text editors and we also saw what is women how to create a file and say we tell them so these are some other options we also saw the visual mode and the command mode command mode does not explain the name command over there but you can type in commands like what I did : q : WQ all those commands you can type in so ownership of Linux file so when you create a file basically in a Linux system you have three types of owners one is the user which right now in my Linux system is Intel apart telepods it’s a user and then there is groups groups are basically you can create a group and add in some users and give them some so that give that group some permission so all that users will have only those permissions and then finally others in processes so processes in the sense when a process is running that process might require a particular resource to work on a particular file to use for that particular process so that process should be given permission to use that particular file so these are the three different types of owners so you can see the purpose of users and groups of our access and permissions so let’s say if there are no users and groups then anyone can log into your system and anyone can use any file access any file even if you’re the owner anymore any like if I am the owner of a file you can log into the system and you can change the contents of that file which is not good for me because it’s my file and I want that content so for that you have users and groups so if my user logs in and creates that file only my user will be given owner permissions only I can edit that file and you cannot edit it because you’re a different user now every user has their own directory every user have their own directory usually the slash home slash user name so under slash home you will have a directory call with your user name in our particular virtual machine you saw that slash home slash intelli pad in telly pad is the user which we created so basically this particular user has a directory under their name and then even processes need permission to access specific files and locations yes so while some process is running obviously that process will have the permission to use a particular file or login to a pod or go into a particular location and access a file so these are the three different types of owners now what is the difference between a user and a group so first user owner of the file and then so these are not the differences these are basically the characteristics of users and groups so first of all let us see the users so users again the owner of the file and then system uses user IDs to manage juices so let’s say there are a hundred different users and in that ten people have the same name so the system will not understand that if all of them have the same name it will think they are all the same user so to differentiate between the users the system has its own identity so system has its own identity scheme which users user IDs so every user will have their own unique user ID whenever that particularly user working on the system the system will check for the user idea I didn’t know who exactly is working on the system right now and then system identifies daemon processors as users so daemon processes or background processes and system will assume that a bagging process is running because a user has induced it because mostly this the user who is inducing it only if user switches onto the system only then those background processes will start to run so now groups groups contains two or more users so all users in the group have same permissions as given to the group so let’s say you’ve created a group or let’s now not assume group so let’s say now you have ten users in that file users or database admins now all of the database admins need the same kind of permissions so instead of providing every single user the same permissions you can create a group ID these five users to that particular group and give that group those permissions so once you give that group that permissions it will be applied to all the users under that particular group so that is why groups are used and then finally groups are identified by GID like how users are identified by user IDs groups are identified by group IDs now others and processes a process can open a file and even read or write in a file yeah it can if provided with enough permissions and if a process is using a file and we delete it it does not get deleted so what is what does this sentence exactly means let me explain it to you so while you are using a while a process is running and it is using a particular file so while that process is running you’re basically deleting that file you would see that that file is not available in the system but the file will not be deleted it will be just deleted are blatantly from the top but from the memory it will not be erased only when the process is complete and the result is successful or if it is failed only when the process is complete that particular file will be deleted from the memory because if you delete that file while that process is happening and you stop that process that is not beneficial for the process as well as the user so this is what happens while a process is using a file and finally there are three types of user IDs effective user IDs real user IDs on se nice so we look at these user IDs in detail okay so first effective you ready so an effective UID and a real user UID is basically the same once you log into the system because in telepods the user which I created and the root are the same person and the UID will be the same because I’m logged into the same system and I’m using both the superuser privileges and the normal user privileges that is super user in the sense when I used a sudo su or su the minuses to become the root and in most of the time while you are running a process affecting view ID is used so effectively you ID in the sense you’re normal UID of the user so the system will understand which user is exactly trying to access this particular process or which shape user is attempting this process using the effective UID and the real user UID comes into play only when you are shifting the user from your normal user to the root user so while you are doing that it is check for the UID it will check for whether the effective UID and the real use of UID is the same or not if it is the same then it will accept and move ahead because sometimes using their normally without super user privileges when you are trying to execute something it might fail and ask for the it might say it does not allow because superuser privileges are not provided but once you use pseudo in front of it and provide the password for it it will work so how this basically works is while you’re not only using it it should take the effective UID and it’ll assume you do not have those permissions but once you provided pseudo and the password it will assume that your root and even though you are root you will have the same UID because you’re just shifting from the normal user to the root user and finally saved user UID is basically once once the system knows it’s the same user and then it will be automatically saved and then once you hit sudo su and the password it will automatically change the user privileges so that’s what save user saved user UID is the first time it might ask you that are you same user please enter the password but once you’ve done that after that it will not ask it directly ask for the password and you can Moorhead so these are processes moving ahead now create a user and groups so that we can understand better so let me open my system so first if you log into it and so right now Internet is not connected I don’t know why I need in general but still I’ll connect it I okay so first you can see this and so this is the user which I am logged in right now and you can see this w it’s the same thing and clear okay so right now I’m logged in as in telepath there is currently only one user because going back under form there is only one particular user which is in telepath because we’ve not created any other user so now what we are going to do is we are going to create another user to a company into the path let’s create in telepods number two Intel apart to and to create that user it’s pretty simple it’s sudo user add user name so let’s go back to the terminal sudo user ID and username into the part two and and the administrator password now it is done so now if you go back to home now you can see there are two different folders Intel apart and Intel apart – because you have created on new user so we’ve created and as the user right now and that’s fine now let me enter into until if I – for permission derived – let me do a sudo and still not able to enter into it thing will have to login before entering trying to enter it okay that’s fine so right now our second step was to create a group so again it’s the same process to create a group pseudo group add and group name I’m going to name it as Group one so I’ve created a group so you can already see there are there is a group called intel afire and there is a Google group called V and V I’ve created a group right now so one more thing so right now try let’s try to do something let’s try with file permissions we have created a user and a group this is a via create so I just wanted to explain that first now let’s try one thing now going back so first let’s try to cat /et see shadow so permission has been denied so going to or PPD you can see here it won’t work but right now with a sudo cat so now you can see it has displayed all the contents under it so why I wanted to explain is this is where permissions come in so you might be thinking how it happens with sudo because I’ve done this a lot sometimes I do it normally permission will be denied but then I’ll use sudo and hint at the password then it will work you might be wondering why it is but basically it is just permissions normally a user will not have permissions to view the contents of an easy TC shadow folder but a super user or root user will have the privileges to see that so that’s what happened over there so now one more thing is how to get super user privileges it’s pretty simple if it’s sudo and su or so you can see now it’s not asking for the password so exit you can do sudo – s so both are the same sudo ICU and sudo – s are the same so now we are logged in as the root user so now let us try so now you can see I’m able to enter the folder into the pipe – but as the user Intel apart I did not have permissions to enter Intel if I – because it is a different user and that user has not provided me permissions to access access his folder now I am the root user so now you can see I can just type in cat et Cie shadow and I will be provided if there isn’t yeah you can see this so I’m provided with the result so why I am provided with the result is because I am the root user and the super user and I have the privileges and permissions to do this let’s go back to the slides so this is how it works now coming down so now root let’s look at the root and it is the directory at the top of the hierarchy so we have a filesystem hierarchy in Linux and root is the top of the hierarchy because root is the first directory under root there are everything else in in a living system root is the main directory under root there are so many directories which are for so many different operations but root is the main directory which is at the top of the hierarchy so it then has a root like structure and under it containing multiple directories and files so it is the ground level for root of the ground level and under root there are so many different branches going under which forms different file structures so that is how it got the name root and this is how this is the symbol of food a slash a backslash is the symbol of root coming down so guys this is how the file structure will be so you can see this is a top folder root and under root you will see all these major folders you can see all these major folders over here so when etc’ has been USR VAR dev home live MNT opt proc and root so we’ll discuss them in detail right now we are understanding file permissions and right now we are looking at the file structure the file hierarchy of a Linux distribution system so here we have root at the top and under root we have other sub directories now let us look at these directories one by first /bin which is essential user command binaries so you can see every single command so you can see gods we can see yeah copy did a go grab hostname kill less LS make directory mount move nano all of these commands are under bin every single command is under bin that is why we use slash bin slash bash even Basha standard min so you can see bash so we use bash to run shell scripts and bin is one of the most important directories which is required so that you can run commands so without these commands basically you cannot do anything else in the Linux system and then et Cie configuration files for the system you have crontab you have the host names you have the network’s you have the passwords here given the passwords are stored you even the time zones are available here the services running or available here you can see every single configuration files in under the EDC folder and then we the s-pen essential system binaries again this is for the user binaries user command binaries this is as bin is for system binaries so you can see fdisk fsck Getti halt if config reboot make swap make filesystem so these are all system based commands so make file system is for let’s say when you mount a particular file storage but that storage does not have a file system in it it does not support the Linux file system then you can use the mkfs command to install a Linux file system within that storage and then you can use reboot to reboot the system and halt – halt every processes if config to view the system’s configurations and IP addresses and MAC addresses so that is what s – and then us are basically its user read-only user applications support data and binaries so under us and the user you can see AB in most user commands under that you see include standard include files for C code and library obj pin live files for coding packages these are basically for the user these are meant for the user even the man pages are under user because a user is going to look for the man pages because if I don’t know a command so let’s say I don’t know what fingers so I’ll just type in man ping and the man pages are actually stored under the USR directory under us are the store under shared under said it is stored in a man so from there it will be fetched and it will be given to me so that’s what starting so you can see you static data shadow will across all architectures so you can share this particular data across every single Linux distribution and it will not stop your functionality and then VAR variable data files you have a cache application cache data so one some application is running or you meet this cache data so without this that application will not know what exactly is happening and once you delete it it has to do the processes again and again it has to store that data in cache even the history command needs cash why you type in history you will be able you’ll be seeing all the commands which were previously executed but where will that be stored it will be stored in the cache and then you have beer lib data modified as program runs you have lock you have the log files you have the opt variable data for installed packages so basically any package you install first it will be so it will be under the VA or opt package and there are temporary files as well temporary files saved between reboots so once you’re rebooting there might be some files which is getting saved so that will be saved and stored in the temporary directory and once you once it is rebooted it will be regained again and then there are some other important directories slash dev slash dev is basically for a device file so if I put in a pendrive I can find that pendrive under the slash dev folder and then there is slash home so slash home is basically a user home directories so that’s what I was explaining you the home directory which has all the user names under it and then live slash lab is libraries so be installed kernel headers and kernel development kernel devil’s in the start while installing the additional the VirtualBox additionals so those additional files require these kernel modules because kernel modules are the files which are required so that we can contact between the so we can have contact between us the shell and the kernel so that’s why we need the libraries and the kernel modules and then /mnt is basically for mounting if a new file system is getting mounted to the system you’ll you can find it in the slash mount directly then again opt is there practice there and finally in one root is their home directory for the root user so even under root there is a folder called root under that folder you will find some sub directories again and that particular sorry and that particular directory is for the root user and that that is the home directory for the root user so normally for a user like in telepath the home directory is slash home but for the root user the home directory slash root so that’s what we’ll have to look at so these the this is the file hierarchy in a Linux distribution in every single Linux distribution this is how it’ll look so understand this particular concept very well so because everything in Linux is a file as I told you / – slash for the device name basically if you enter a pendrive again that pendrive will consider it as a file in the Linux system so every single entity is a file in Linux so that’s why files and file permissions are very important in Linux this is a lot about file permissions users and groups so now let us look at these two commands which are really important and highly used commands which is chmod and CH owned which basically it’s CH modifications and CH ownership so these commands for highly use now let’s look at these commands so first modifying permissions chmod is the command which you can use to modify the permission of a file or a directory so you saw that read permissions rather than write permissions and all that so let’s say you have a file and you have written rate and you don’t save it now you don’t want anybody to write inside that file now you can basically change your file functions and remove the write permission from that file so that even you cannot try it inside that file unknowingly so that’s how you can use it and to add or remove a permission you can use plus or minus so you can see some examples in the band you can see chmod you plus X 1 point txt and doing an LS minus L 1 point txt basically what it did is it removed or it added 4x over here and it removed X from both of these places and then again chmod u minus X 1 minus T XE so basically this particular file did not have permissions already so that’s why it is explaining that this place is empty and then while removing minus X that is execution it removes X from every single place of this entire permission so RW – RW – r – – so X was removed from every single permission that is the user permission the group permission as well as the other or process permission and then another way to modify permissions are providing numbers now numbers let’s say 4 is read permission to write permission and 1’s execute function so here you can see our W and X so R so our W and X so the addition of our W and X is 7 that is 4 2 & 1 it is 7 so now coming down so you can see here chmod 755 1 dot txt so now what would have that what this would have done is 7 in the sense it is 4 plus 2 plus 1 which is 7 that means give all reader access give all reader access and 5 means it is 4 plus 1 then it is remove right axis from group permissions and remove right axis from other permissions so that is what 755 means and you can see here RW x the read permissions has every single for me the group permission does not have right as I said and even the that permissions does not have right as I said so now you can see it but what is sine Phi Phi there was no 7 or Phi over here so now coming over here 4 plus 2 plus 1 is equal to 7 so all access is permitted so that’s what happened here in the first place that is 7 then Phi which is basically 4.0 4 plus 1 is equal to Phi read and execute permissions so that’s what was provided in the second and third options but we do not use 6 overview 6 basically provides read and write functions and it does not provide exhibit promises so this is one more way to change it one way is to use plus and minus second ways to use numbers in the then ownership permission ownership permission is ch own so like modifying the files functions we can also modify the users and groups ownership of the file and for that we must use CH on so you can see here again LS minus L 2 dot txt so forget about the part where we saw the file permissions now just concentrate on this particular part which is root and root which are basically the ownership of this particular file so 2 dot txt you can see the ownership was with root and root so now I wanted permission so I use the command see its own cody to Rohtak see and you can see the change over here so even as usual Cody I’ve got the permission to use this particular file called 2 dot txt so this is how you can use CH on and there are some other ways of doing it so now you can see here CH own user name file name ownership of file for user so let’s say I created a file but I want so let’s say in telepods created a file the user in telepods and this particular user wants to give that permissions to in telepath to user so now this particular user in telepods can simply provide CH own in telepath to and file name and the file permissions will be provided to that particular user and then there is CH group and group name and file name so CH group is basically changing the ownership of a group so if you have greater group you can use the command chgrp and group name and file name so that that group has the file permissions so let’s say this to dot txt that particular file will have so every user under that group will have permissions to either access or not access that file according to the permissions provided and then see its own user name colon group named file so now both user and group at the same time so let’s say you want to give permissions to a user who’s not in a group and also to the intent group so now you can use this way of doing it CH own username : group name file name so this will give permissions to go to the user as well as to group now hands-on chmod and CH own let us do this in the console you know let us proceed with the hands-on part so let me open my it’s just little bit slow this is is really started so I’ve restarted it but you know let’s get started with CH more and CH own I’ll open the terminal then we execute few examples of how you can use chmod and how you can do CH own now let me first open the so here I will do this will do the chmod part first so I’ll create a file then after creating a file will change some permissions and check whether it changes or not and then we’ll change the map to that we’ll use numbers to do that and after that will you chmod to change the permission of a user as well as the formation of the group so that will do and I’ll going back here opening the terminal so first let me make this bigger again so I made it bigger okay so now let’s start off with it so first let me create a file Todd so as I told you touches just to create a file I’m going to make it as load or txt or just file one dot txt I have created the file and there is a file file on dot txt LS minus L so this command will explain me whether about the file permissions so you can see it has read/write permissions for users read/write permissions for the group and only read permission for processes so the user isn’t any pad and the group is also Intel affected so now I’m going to use chmod to change this to chmod u plus X this is just for the user you plus X and file one dot txt so done now again al is L so now you can see I’ve added the exited permissions just for the user so now let me do one more thing now I’ll do for G for the crew sorry now let us try yeah so I’ve added it for the group as well so now let me add the write permissions sorry let me remove the write permissions from group so done so you can see I’ve removed that I permissions from the group but I have provided the execute permissions so now I want to remove write and provide only read for others or processes for that it is full and it is going to be amount of room you are and I’m going to I tell you I get zero instead of oh so done so now if I do an LS so now you can see I have provided only W the right permissions for others or permissions of C sorry others or processes this is what I did using chmod so now let’s do one more thing so now in give permissions using numbers now I am giving seven seven seven so what does seven seven seven me 1077 is basically providing every single permission to that file so five ones or txt so now if you view it and when you can see this particular file has every single permission so let me change it to seven five six toward will this do so this will they still make this well it will remove the write permissions from group and this six will basically remove the execute permission from others so let me hand out and I can do an LS L so you can see it took up the write permissions and it took off the execute permissions now let us do one more thing so I will remove the write permission from the user so let’s say our user is in telepods so I’m going to remove the write permission from this file which basically is three only right sorry if I remove that permission it is with pipe read and execute so I’ll give five five six it’s going to be the same so now yeah so only a region and executors there now let me open this file and you can see it is unraidable because the user does not have functions going bad let me change this once again I will make this I’ll provide write permissions as well as we need an execute because they are already available so now let me try nano again so now I can write because I have provided the permissions to write so this is how you can use chmod so let me just close this okay now we’ve done chmod let’s do CH on so while I’m doing this LS l v one dot 60 you can see internal pie and in clip at over here so this is the user and this is a group for your graded items so now let us change the group which can access this file so the CH on and the group name so first I don’t know the group’s so I’m going to turn this going to do a cat group so it’s Intel about to Intelli 5-3 into the path there are no other groups so what I’m going to do I’m going to create a group to group add them I’ve created a group so now let’s try this once again but this time I’m not going to that I’m going to get up there so a group is all available so we’ve created a group now we’ll have to add users to this group so I’m going to add in telepath so sudo G password so you’ll have to provide this for ID it’s minus 8 then you’ll have to provide the username which is going to be in telepath and then the group name which is a depth for adding user ID back to group them it’s added so now we can check by English and it is added you can see that over here so now we have created a group and added it now let us change the permission of finally yeah so now let us change the permission of file one dot exe so this particular group in Delhi pad is going to change to group del so to do that it’s simply C as explainn so we saw this file name sorry user name and group name and fine name this basically is the syntax you can provide the user name of you group name over here and file name over here so right now we just want to change the group name so for that we can either give the group name like this there and I 1 dot txt so it needs so now it has changed now let us check file 1 once again so now you can see Intel apart and Dev the group name has changed so we have done that you also have another option to change that so you can use this command CH group and group name so now checking once again now you can see the group has been changed back to in telepath so the same way you can also change the file owner so see its own and interview part – now let’s check now you can see the user has been changed – in telepak – because we change the file ownership so now let’s do this I know Phi 1 dot txt and do an LS so you can see there are I trade a wrong file I have to open file 1 dot txt so you can see it is unraidable for me because I’ve changed the permissions to Internet by 2 that is another user so right now I don’t have permissions but so let me change it once in sudo CH own Intel apart and filing so now if I open file one but txt I should be able to write yeah because I’m the user who has permissions over this file right now so I should be able to write so done so CH own and chmod if these are the operations you can do with its own chmod it’s very helpful and I think you didn’t use this so let me go back to the slides display contents of a file we have various ways of doing that we’ll be looking at some ways of it few few different commands to do that ok so these are the four with commands which I wanted to explain first head first 10 lines and then tail last 10 lines grep searches for a pattern I think we’ve used grip multiple times already then cat again we also use cat but we will not use head and tail so we will do head and tail so let me go to ok so now let’s see if I have any files here I have demo dot txt for cell to head they know dot txt so we can see it’s explaining the first five lines but head basically explains the first 10 lines so what I’m going to do is I’m going to open demo dot txt and I’m going to enter multiple lines so that it will be easy for us to debug so there are so many lines so I’m just going to make these bigger lines okay so it’s fine I’ve done it ok so now let’s do head once again and you see now it explains only the top 10 lines for the first 10 lines and the tail command the tail command will explain the last 10 lines so you can see that as well tail command explains the last 10 lines now grip ASD demo dot txt so you can see grip is finding a pattern called ASD and it is explaining all those lines which has that put it in the pattern so let’s just type in tofu it again found a pattern so that’s why you use grip and then finally we have chart that basically provides the entire file so you can see that over here and one more few more things you can do with the tail and header I think in tail you can use the end command to sew so you can see it explains only the last four lines and in head again you can do that and it explains up first file ends so basically you can use these commands to display the contents of the file as well as track them so using grep you can see every single instance of a particular name inside a particular file which is very helpful for recognizing patterns so that’s what we did right now so for example I will open the motor tx2 once again okay so I’ve opened demo dot txt now what I’m going to do is I’m going to enter the username which is in telepath in various places it’s telling okay so entered in three different places so what I’m going to do is I’m going to use grip to find it but I’m not going to use my username directly I’m going to use a meta character dollar and the command a command called Who am I which basically reads the username to grip Who am I demo dot txt so now you can see it is reading my username and then it is using my username to find a pattern inside demo dot txt here we are using both the displaying contents for finding a pattern we are using grep as well as we are using the who are my command and also we are using in meta character to basically read the Who am I command so if you just type in Who am I it searches for Who am I if you put the dollar command and see the dollar might a character in front of it basically it means that the value of Who am I which is intellibid so that’s what it does so this is how you use tail head grip and finally cat you can do all these operations using all these commands there are still a lot of commands but these are the most basic commands let me get back to slides so we’ve done this next is copying a file moving a file renaming a file and deleting a file let’s start off with copying so I’ve already explained you copying and move but still we’ll look at them again first copy copying files the command is CP CP then source then destination or CP source to directory so these are different ways of copying and CP souls one source to source n so you can give a number of files and copy them to another directory so now let’s execute these copy commands let me open it okay so first let me create few files file can I name them demo one to txt the mode or I’ll just give demo one demo to the mode three so I think I’ve created three files see I’ve created now I will do a nano of demo one I will put hello and I’ve saved it next demo – I’ve typed in something and there more three same thing I’m typing some other sentence and I’ve saved them so all these files are saved right now so first let us do a copy within the directory that is copy demo one to demo for so now duo and LS now you can see there is a demo for file also before it was not existing now there is a demo for file and if I do a cat of demo for you can see the text same as demo one so next copy they move to inside desktop let’s move inside desktop so I’ve copied it right now you can see demo 2 will be available here as well as desktop so you can see the motive over here as well coming back next will copy multiple files into another folder under the directory that is first demo 1 demo demo 3 in demo 4 we’ll move these three files inside downloads sorry so done so right now these files would be available here as well available in downloads as well so you can see these files are available over here so you’ve done copy next we’ll do the move command so again move has the same functionalities so you can see that over here it has the same functionality it’s the different command but the same syntax so now let us move a file within the same directory that is demo 1 I’m going to move demo one to demo file so now there will not be a file named demo 1 anywhere here there will be only a file named demo file because I moved the contents of demo one as well as the file itself to another file named as demo file next I’ll move their move 5 into another I’ll move to desktop so now you can see demo Phi is not available here but if I open desktop I should find the file over here because the stock is over here next I will do one more thing coming back will move multiple files so they are more 3 demo 4 I’ll move these 2 files into documents too many arguments sorry I provided a wrong I provided the wrong command at this move and done so right now demo 3n demo 4 will not be here but if I go into documents they’ll be available and you can see them over here so this is all you use move and copy now going back now renaming a file to rename again it is the same command as move so let’s see rename once again so let’s say I’ve created a file name so I’m not going to create another file so let’s say I have one dot txt so I want to make this as the word that is oh NP dot txt one dot txt so I’m going to use Move command one dot txt – one dot txt so now you can see there is a file named 1 dot X but there’s no file named 1 dot X because I’ve renamed it but here the process is not actually renaming the file it’s actually moving the file but you will have to use the Move command to rename the file as well and we’ve seen rename as well now deleting so now to delete it’s a pretty simple first RM RM is a command remove remove and file name then to move and I the driven star dot txt so what this does is it will delete all the dot txt files then remove source one source – you can also remove by providing different file names now we’ll try all this so first here you can see you remove demo – I will do mu demo to demo to is removed then I will go inside documents and yet there are different types of files so I will remove them by typing in demo 3 demo 4 + 2 dot txt and now I’ve removed these as well now here let me go inside desktop sorry and there are two files over here so I think I can delete them using this RM star now you know do that I think you can do this remove power and demo so it’s not considering it so let’s leave that okay so now let’s remove these files normally first demo – and demo file it’s not there so now what I wanted to do is so let’s see there is what demo dot txt as well as file 1 dot txt as well as one dot txt so I want to remove all the txt files in a single go for that what I can do is remove star dot txt and so this will basically remove all that dot txt and file so I’ve removed all those files so we have seen how to delete files as well and now common commands make directory we’ve done this remove directory and then find searches of file or a directory so let’s use find find one dot Sh so it is explaining that it is existing so if I search for one dot txt it will not exist so let’s say find so first let me open this thing nothing will be here so there is gamma one let me search for demo one but it will not find because it’s not available here but find demo one I think if I provide documents sorry if I provide downloads again sorry so it’s finding downloads and it also explains the files under downloads so this is one command which is really useful it will explain the directory as well as the sub files and subdirectories of the directory and then there is PWD which we have done already then file explains the type of the file so going ahead to file downloads so it explains it’s the directory no file was let me see yeah yeah one dot is H so file one door Sh it’s a shell script now let me create a text file and file one dot txt so it’s an empty file because I have not entered anything and so that’s what it means so here you can see it’s born again shell script and this is directory this is empty file so that’s how you use file UNIX process controls commands or Linux process control commands so moving ahead you can see here a command issued in Linux starts a new process which invokes a five digit unique ID called process ID or PID using the process ID the process can be tracked so let’s say if you type in a command that particular command will invoke a process so if a process is invoked obviously that process should have a process ID so once it invokes that ID using that ID you can track that particular process it is basically reversed checking it so let’s say I am trying to find out a pattern in a particular document or I am trying to do an LS or I am trying to find the present working directory provided here PWD so when I type in PWD and hit enter obviously it will start a process by using that processes unique ID so once that happens once it is called that particular process can be tracked using the process ID so that’s what they are meaning to say here so now initializing a process striking a process stopping and other processes so we look at these steps first initializing a process a process can be visualized in two ways foreground and background so foreground every process runs in foreground by default when it has started so when I type in PWD it will explain you the output in the terminal so it is a foreground process fronts in the background allowing other processes to run in parallel so basically let’s say in another terminal there is another command running and this terminal you can use an and in the back which will basically push your command to the background so now it will be a background command so let’s do this may open the terminal and I will zoom it in so LS PWD and no such file or directory so so PWD basically is a foreground process and PW and will become a background process so you can see here 1 1 2 1 5 is the process ID for this particular process so firstly then walk to the process ID so it checked whether any process is running in already running or not if it is already running then it will run parallely if it does not it will again execute it and explain you the result so the result is over here and it explains it’s done so this is what it means so normally when you run any command it will run in the foreground once he use an and in the end then it will become background so let’s do for LS LS dollar C sorry LS and let’s do this LS and type PWD and so I think I’ll remove this and I will put Turner and here so you see the second process has completed so let us try once again LS PWD so now you can see it first did this particular process but it did not do the second one because it took the R so now let us use and so now you can see it did both the processes that is it first did LS then it did PWD but it did it in a single go basically it considered it as a single process and it executed it but it also considered it as a background process that’s why to explain in the process ID as well as the done mark now going ahead next tracking a process to track a process you have the command PS we look at these commands in depth in upcoming modules we are looking these right now like we’ll be looking at these a little bit but in the few coming upcoming modules we’ll be looking at these commands in depth PS and there are still top there are still more commands we’ll be looking at them in depth later right now let’s just go go ahead with the presentation so next all running processes can be tracked using the following commands PS so now let us try this command yes so you can see two processes running one is bash 1sps now if I do a PS ox it will explain every single process which is running so you can see that over here the root process who is running the process the process ID and this is basically an onion sorry this is basically a none interactive document it explains all the processes which are and the process ID and it explains every single thing even it explains PS ox as a process so it just explains all the processes which have done which is running every single thing so that’s what awesome it’s so even PS explains the current running processes and let’s say PWD and and I will do a PS so right now it won’t explain because it has to run in synchronization only then it will explain going back so this is what what this is why you use PS or it will explain all the running processes so for example I can explain this so let’s connect to the internet okay so let me zoom this in now I think google.com I will teach both the ping command lane the later modules now just so you can see pink is running so now let me do PS think it is not now it’s running here so let me open another tab and do PS so it’s still not explaining it so PS ping so I can do this so let me close this right now let’s let ping run I’ll close this so let me open another terminal and I can make it bigger so now let me do a PS so now you can see another process was running meet this figure you can see every single process which ran in this particular system and you can also see their process IDs you can see that over here but the current processes which are only running only that PS will explain nothing else because it’s not an interactive command it is basically a document so let’s leave that next moving on next another command is there so you can see a running process can be tracked using the following commands so you can see uie PID PID C s time terminal time cm cm D basically this is the command so UID is basically the user ID or the ID of the user running the process and then second is PID the process ID so you can see the process ID as well PP ID is the parent process ID if this particular process has a parent let’s say you are running Firefox then opening ten different tabs so it might have a process ID and then sub IDs and then C is CPU utilization of that particular process so here in this case there is no CPU utilization and then s time is start time of the process when the when did this particular process start and then TTY is the terminal associated we are using only one terminal that’s why it’s explaining pts / 0 its 0 terminal and then time is CPU time taken by the process how long it took basically we did those processes did not run and it did not take much time so that’s why it is explaining 0 0 0 0 0 0 and finally CMD is the command of the process now this is what I was explaining you PS aux lists out all the running processes for all users it not just explains for this particular user it explains the running processes for every single users right now that’s what I explained you PSO and then PS – you user name will explain all the running processes for one user so this is an interesting command so we try this so PS hog States – you so either need a oxy – you and Intel apart ok so right now it’s explaining every single process running under intel pad you can see that printing mouse key box client the hash normal so this is the terminal that’s what it’s explaining Lecter let me run Firefox and let’s try this once again and now you can see Firefox is also been added so basically it is explaining so if they do PS it only explains these two if I see for the user it is explaining Firefox PS bash and chrome terminal because all of these are running currently so so I will just close this I will require now if I do this again it should not explain Firefox because I stopped it so it was explaining web content as well so right now as I closed it so the I close it so question here no I did not that’s why it is still explaining close tabs and so let’s run it once again so now you can see there is no Firefox because we’ve closed the process so this is one way to track the process under particular diffusor you can check that and then the next one is stopping a process so let us do this so let’s again run Firefox and so you can see the process ID over here let me run in once again because it will explain a single process ID so I can use that process ID to kill the process and it will automatically close this particular console so now you can see Firefox this is the process ID I have copied it going back so let us understand the let us understand the syntax first if a process is running in the foreground that means let’s say you’re running things so if you’re running ping if you hit control C which will it which is so keyboard interrupt it’ll automatically stop the process for example let me do a ping in telecom so now if I do a ctrl C so you can see it automatically is terminated it so now this is one way of starting a process the second day you see is to use the command kill so kill terms signal so this is where you enter the signal and this is where you enter the PID so signal is what tells what exactly this particular kill command should do in order to stop a background process use the following command so coming down take a look at the list of terminate signals so let me give kill on the cell so this explains every single signals available in your Linux distribution so you can check it over here sig Hogg sig end sig buzz and then there should be a shake abort signal is their sigil arms that’s it stop is there so all of these are different signals will be learning about signals as well in the further modules and then there is a cat and command so example stop the cat command running in background by so we’ll do this example we’ll run the cat command in the background so once we have run the cat command at the background then we will kill this process using its process ID so that’s what we are going to do on so let’s go ahead and do this so I’ll close this I will open another window I will run the cat command it automatically stopped I’ll just copy this so now P sorry killed and I think we should use the number of nine – nine so – line is basically terminate the process abruptly it will kill the process of roughly and minus nine so it was already stopped so it killed the process so you can see right now there are two processes so one is let this run will close that as well let me do the spring clearly part calm so let this run let us do a PS right now it’s not explaining but we have the IP so I’ll just copy this still running so let’s – nine and the ID I think this is the ideal little chip once again and I’ve pasted it so I think it would have killed the process see how the process stopped so they feel it killed it so now let us do the same thing with Mozilla so now first I’ll do PS walks and you can see every single process running and for Firefox you can see here on Firefox Firefox content Pro Firefox content flow so I’m going to just stop this particular I’m gonna kill this so kill – 9 which is for terminating or sigga sigga bot so this will basically so sorry it is sick kill this will basically kill the process so kill – 9 and I’m pasting it and you you saw the mozilla window with this disappeared from the behind basically it killed the process so let me do a PS ox once again so now you cannot see the Firefox process running because I have killed it so this is all you can use the kill command to kill the process so we did that particular example to use Mozilla and we saw how to kill a process right now we saw up till PS the command PS now we look at top and few more commands so first top so the following command is used to see all the running processes within the working environment of Linux basically this is an interactive shell you can see the processes changing in real time so if a process is killed you can see that in real time if a processes are invoked you can see that in real time you can use the top command for that so we’ll do them one by one now let us just see what are the commands available sorry so next we have nice so you can see the following command is used to start a process and assign it a priority value at the same time so nice – nice value and process so nice value ranges from minus 20 to 19 where minus 20 is of the highest priority so you can see that and it started the process in the background and then PS minus L it was explaining all the running processes and you can see priority is 80 nice value is zero default priority is 80 and the command is can so you can see all the priority values over here and you can see cata stopped over here coming down you can see nice minus 19 cat and so basically what this will do I say as we told you minus 20 is the highest priority so minus 19 obviously will be the I is priority right now so you can see the priority has changed from 80 so here we can see the priority has changed from eighty to ninety nine nice value is nineteen priority is reduced to $2.99 and this is again cat and nice 19 cat it stopped again so and again one more is nice – – minus nineteen command so nice – – nineteen plaid and so again it started the cat it started running cat nice value is minus nineteen and priority is increased to 61 so that you can see over here so this is what – nineteen does so if you just provide – / – any value it does not consider it is so it does not consider it is it has or – 20 value it basically considered it has a positive value will have to provide two hyphens only then it will consider it as a – value which means it increases the priority of that so this is 99 and this is 61 basically which means this has increased the priority so now the one more command is realized you can see the following command is used to change the priority of a process so while that practic particular process is running you can change the priority of that particular process so be nice again the same – nice value then process ID so let’s say a process is started with a nice value of minus 10 now it’s minus 10 cat and so nice – 10 cation so that’s what they’re doing here nice – -10 cat and so this is the process where dsl at 70 ni is minus 10 coming down now using green ice – 3 and the process ID basically they change the value automatically so you can see it got changed old priority was – then new priority is minus 3 so 77 minus 3 and that’s what they are telling here so but what do you mean by priority why do you need priority so let’s say if a process is having the highest priority CPU will provide the maximum time for that process to complete but if you provided that particular process the lowest priority of 19 then that process will not be given the same priority as a process which has minus 20 or some value nearby that so that is why you need priority so now and then one more command is DF this command basically lists the block devices available on their disk space so you can see these are the file systems so now let us start off with the first command and look at all these commands and let us finish you off with this particular module let me open my done I opened it so let’s start off with the first command which is top so as you can see top command is running and you can see the values are being changed top gnome shell nominal so let me open another window and let me run pink dot-com so I am pinging right now so there should be a new process created Bing so I think it just went and it went back right now it’s explaining the top processes over here to start so let me stop this and one once again think you see the changes going on here okay let’s stop this now let me become the super user and run a command in the background so let me run cat and so cat is running in the background so right now it should explain a cat command if it has enough CPU memory so you can see here PID priority is 20 minus 51 then ni are these processes of the highest priority because they are minus 20 and then what else you can see the now the time which are these processes are running and you can see the memory which this particular processes are taking the shell is taking 11.5% of the memory and 19.4% of the CPU at this particular time top command is taking 1.7 percent the gnome terminal is taking one point seven percent of memory and one percent of right now it’s saying three percent of the CPU so you can see this is an interactive way of looking at it and you can see the number of tasks running to thirty to thirty total tasks two are running three are running to twenty five sleeping two are stopped and the memory 2837 three memories 637 used just thousand 73 and available memory is thousand eighty so you can see the real-time changes in the CPU memory available and not available so let me now stop this kill – 9 1 – 8 – 1 so I’ll stop it so the cat command should stop and the available memory you saw it had a slight increase because one particular background process stopped and that gave the memory a little space so this is how topped works now let me close this and so we saw top next we will have to seem nice so going back here so nice and the value so first let us run cat in the background and then let us do the same process over here so I am just going to open this – I’m already logged in as the root and sudo sorry I’m already the root so I’m going to run a process – 19 cat and so now I’m going to do PS – L and now you can see the cat process running which is – 19 19 and 19 so first let me stop kill few processes no sorry I should not kill it now I’m going to do the same thing but I’m going to use – – 19 cat and and PS minus L so now you can see there is a fourth cat process which is running with this different PID but the parent process ID is the same because I told you all similar processes will have the same parent process ID but will have a different process ID so first let us kill them 1 3 1 5 2 done 1 3 u 1 7 5 done on three one seven seven done so right now only one seven eight is running so the 1 1 sorry 1 3 0 8 6 process is running so let this run so right now what I’m going to do is I’m going to realize this process so that’s what we’ll have to do that is rename we did both of these commands we’ve changed this particular value so now we’ll use 3 nice that is you can see really nice – 3 and the process ID so I’ll put 3 nice so I’m changing the niceness basically I’m changing the priority so that the CPU will give memory and time accordingly so V nice I’m going to give minus 6 and I’m going to give the process ID cross ID is 1 3 u 1 0 sorry it’s 0 8 6 enter so now the it’s explaining old priority is 19 and new priority is minus 6 if you do a PSL again you can change you can see now the process ID has changed on the priority has increased to 74 so this is you use realize and then finally there is a DF command so let me create this and hit DF so now you can see there’s a /dev which is mounted it is completely available because no other depth device is touched then there is slash run and there is slash boot so boot is the directory which is used for booting the system to basically to start the system without the boot directory you cannot start the system and there is run user 42 + thousand so thousand is the user ID of in telepods user so that’s what and there is a fourth one for the guest additions so the guest additions is running and the use is 100% this particular directory is used hundred percent because it’s running all the time so this is how you can view the mounted devices the device files as well as the storage which is used by them and the storage is available and you can see the mounted location also so this is route so you can see in the root so this is the root and you can see it’s mounted to the root folder and eleven percent of this particular root folders the space is used and you can see the available storage and the u storage so this is how you can view it so now we view all kinds of processes going back so we’ve completed this module guys so thank you meet you in the next module so let me just recap the last part we saw the PS command we saw the PS aux command which lists every single process but top is the same kind of a process but top will explain that interactively PS ox will explain just the processes which are already which are running when that particular command is typed in once that command is type in and you’ve got the result after that if there is a new process it will not explain but the top command will explain that so top is an interactive running to explain the running processes it’s an interactive command but PS is not and then nice and green eyes or commands for changing the priority your processes so it will decide how much priority should the CPU should give to this particular process so according to the nice value and the renames values so Riina’s is to change the nice values so the highest priority is -20 the lowest is 19 so accordingly it will prioritize the processes and run them accordingly it will give the maximum memory and time to the processes which have the highest priority to complete them first so that’s why you can realize your processes if they do not have high priority or if they have high priority and then we also saw this command which is skill we used the kill command by using – the 9 and the process ID we can stop that particular process completely and using and at the end you can basically run a process in the background so that we saw and it only works if you are logged in as sorry not logged in if you are a super user only then you can run the background process otherwise you cannot do that it will automatically stop itself and then you can also use control-c which is basically an interrupt keyboard interrupt that will also stop it and then yeah so this is what we saw in this particular module okay guys a quick info if you want to do an end-to-end Linux training in telepods provides a complete in the next certification training and those details are available in the description okay guys we come to the end of this session I hope this session was helpful and informative if you have queries regarding this session please leave a comment below and we’ll now to help you out thank you

ll look into files editors