DevOps Interview Questions | DevOps Interview Questions and Answers | Intellipaat

[Music] hello everyone welcome to this session on the ROPS interview questions today in this session we will be talking about so the top asked interview questions by industry professionals while they're hiring DevOps engineers now these questions have been collated by talking to top hiring managers who hire DevOps and cloud engineers day in and day out so without wasting any time let's go ahead and get started but before we move on to the agenda guys if you haven't already subscribed to the intellibid channel please subscribe and click on that bell icon to never miss out on any updates from us so now let's move on to the agenda so first of all we will be talking about continuous development questions and then move on to discuss how the virtualization and containerization questions that can be asked to you while you sit in an interview after that we will be talking about continuous integration followed by configuration management and continuous monitoring and finally we will be discussing some questions on continuous testing okay this is the agenda for this video I hope it's clear to you now let's move on and talk about a first topic which is continuous development so our first question asks us can we explain the gate architecture now this is fairly an important question reason being only if you understand the underlying basics of how gate works will you be able to troubleshoot a problem when you face it and when you are working in a company as a divorce engineer alright so let us try to explain what it basically is and how its architecture is now most of you might know that gate is a distributed version control system now what is the distributed version control system let us explain it using a diagram in a distributed version control system basically your repository it is distributed among the people who are contributing to that repository and that is why it is called distributed so that means that anyone who wants to make the change in the code that is present in this repository has to first copy this repository on his local system commit the changes to the local file system of this repository and only then he can push this repository on to the or push the code to changes or the feature editions and everything to the remote repository right nobody can work directly on the remote repository and this is the main principle of how gate works and that is the reason it is called a distributed version control system right if you were to talk about the lifecycle as to what are the steps to implement if somebody wants to say upload or change some code present in our remote repository the first thing that I have to do is pull the repository from the remote system once they pulled the repository it becomes their local repository change whatever files they want to change and then once they have done with the changes they will have to do a git commit or they'll have to commit the files to the local repository once the files have been committed they will have to be pushed to the remote repository so that it becomes visible to anyone and everyone who will pull this project the next time all right and this is how the whole gate architecture works now I hope you guys understand what is the working of gate and what exactly is the architecture of it moving forward now let's talk about the next question which says in gate how can you revert a commit that hasn't already been pushed and made public right so basically you have done some changes in the code you committed those changes to your local repository and now you've also pushed the changes to the github repository now if you have a CI DCI CD pipeline in place which basically means that the moment you commit to get it automatically takes the code and deploys it on a server if that is the kind of configuration that you have done then probably the code that you have pushed has also been deployed on a server and that is when you repent you know you come come to sense that you know the code is wrong and you quickly have to change the code so that everything becomes working again right now this is a very hot fix or this is a very quick fix that probably every dobbs engineer employs when they whenever there is a problem in the production server right so what is that quick fix the quick fix basically says that whatever commit whatever last commit was working perfectly just roll back to that so that everything becomes normal until unless you have fixed the new commit that is the basically the intention behind the revert procedure now how can you implement the word procedure it can be implemented using the get revert command and let me show you a quick demo of the get revert command so you know how you can implement it in a computer all right so this is my terminal guys basically I will SSH into an AWS over and I'm in so I have a github repository that I have created for demo purposes so like we discussed the first stage in the lifecycle of git is to clone the repository so we'll just copy this address so we'll just copy this address one second yes so we'll just copy this address and then we'll come here and we'll type git clone and then the address okay now this project is basically a website that I created it's a small website that I created now in order to see that website we will have to paste this code inside our Apache folder so let us go inside an Apache folder which is present in this directory all right now I'll do a quick git clone along with the repository address hit enter and now if I do an LS you can see that this is a folder called DevOps IQ which has been created inside this folder I will go inside DevOps IQ and do an LS and you can see there's one more folder called above psych you alright let's go inside that and now if I do an LS these are the two files which are present inside my codebase okay now if you were to see what this website actually looks like right now I can just go here and I can type in the IP address so it's 18 dot triple 2.12 3.58 slash DevOps IQ and slash dev ops IQ all right this is how the website looks like for now now I have to make some changes so that the background becomes a little more better so what I can do I'll just go back here I'll go do a nano and change the code of the website and say I'll change it to I have an image in the images folder let me change it to one dot jpg all right let us save it and once you have saved it the next thing that you have to do is commit the changes to your local repository and let us do that so first I'll have to add the tip files to the repository now I'll have to commit the changes and the message should say changed background all right so the changes have been committed and now I'll push these changes to the remote repository so it's HS har and the password is this now before making these changes let me quickly show you the code that you are currently going to see before I push anything on this repository so can you see the code is images slash two dot jpg I've changed the code to be one dot jpg so let me hit enter and let's see if our code gets changed over here so now if I do a refresh let me do ru fresh you can see the code has been changed just now so it says 44 seconds ago the code was changed awesome so now because my code has been changed if I go to this website now and hit enter you can see the background is now changed it is now a different background now what I want to do I want to I realize that this change that I did is probably wrong and I want to revert to a particular commit to the older comment that was actually working all right so what I can do is I'll just come back to my terminal let me clear the screen first thing that you do is do a git log so now you get to get a log of all the comments that you have made to this particular repository now this is the particular commit that you have particularly applied right now and this is causing you a problem so just copy the commit ID for this and now just go ahead and do a git revert so get the word and then give this ID which you just copied okay and hit enter so once you do that it'll tell you the information about this particular commit ID right so just review everything and then you can see that the comet has been reverted so now I have not pushed the changes but then if I come back here and if I hit enter you can see the older website comes back because the code has now been changed and if I want to make these changes to the remote repository as well all I have to do is git push origin master and will ask me the credentials and the changes have been pushed right now if I come here and I just see the core can if I do worry afresh you can again see that the code has changed back to 2-door jpg which was our earlier code which we made changes to all right so guys this is how you can do a revert on on a basically a commit and a push that you have made to your remote repository as well right so if you encounter any problem during working a while working at the DevOps engineer you should remember this session where I taught you how to divert a particular commit all right so with that let's move on to our next question which is have you ever encountered failed deployments and how have you handled them now see they any DevOps engineer in the world will have faced a problem in which you know probably the things that he had planned the things didn't go according to his plan right that absolutely happens and if somebody is asking you in a DevOps interview have you committed mistakes so you should just to impress them probably never say yes right so if you have never committed mistakes that's awesome right but then I know that every engineer or every DevOps engineer was working the nursery would have faced a problem while working and would basically account to a mistake that he made while deploying things all right now the important thing or the important key takeaway from this kind of a learning should be that whatever mistake you make you learn from it right and you never commit it again and that is basically the intent behind this question as well the interviewer would want to know if you made the mistakes what did you learn from those mistakes okay so if you if an interview was supposed to ask me this question also obviously I have encountered failed deployments and what have I learned from them I'll just give you the best practices that I think are viable for any DevOps engineer who is working in the industry so the first thing that every one should follow and should make it a thumb rule is that you should automate code testing not only does it save time because now you know your tester does not have to wait for your developer to basically push the code and then check it the developer can check it in real time because you have written a script for his web for his application and all the major tests which are to be done which are pretty common can be done using automated code testing right now like I said it's not only for time saving but also it removes the the part where and humor human error can occur right so if if you are working if you are now you know when you work with people people commit mistakes but if you can write a code which will basically test each and every functionality that code will never make mistake and that is why you should always automate things as far as possible right so like in my example the what happened was that there was a basically commit to the repository which was basically a feature edition right and the tester did not see the all the functionalities of for code to see some of the functionalities that could impact the other components of my product and because of that when it got pushed onto production basically disaster happened everything stopped working right and that was only because the testing did not happen properly right so for all the critical processes of your website or your product you can basically create a code which will test that website and basically that that would amount to that would be basically closed on most of the doors to mistakes all right the next thing is you should always use docker for same environment right and this is basically the ideology behind devops that these kind of problems where you know a developer used to work and a tester could not run his code on his computer but the developer said that everything is working fine on a system docker basically solves that problem right so use docker as much as you can for the same environment problem that you might face then we should always use microservices now when you are working in a company it could be that you know the product is in the legacy phase and hence it's on a monolith kind of a thing but you should never encourage this kind of an architecture right a reason being say you did a bad commit or you did a bad push on the production server but it should not impact the other components of your product right if probably you have done something to search and if it's a bad commit or a bad push the only functionality that should be impacted should be your search functionality and not the other functionalities and then that is the sole reason behind why we should use micro-services that is we should divide our application into different small products which we would deploy on servers and these products should be independent of each other when you talk about the monolithic architecture all these components are coinciding which other I have the dependency upon each other but when you talk about micro services kind of an architecture you remove that dependency so as to even if one component fails it does not impact the whole application fourth point being you should always overcome risks to avoid failures now this basically means that if there is a code change or if there is a future edition which works some time then sometimes it does not and you're not able to figure out why is exactly that thing happening it is better to wait and troubleshoot it than to push it just to meet your date's right because the latter can cause you a big problem in production when you are in a company like probably like ëtil or in a company like Samsung or Ericsson where their products each second of their websites uptime brings in money right so if your website is down for 30 seconds that could amount to a huge loss and that would be on you right so - for you to not face that kind of a situation always be 100% sure before would you make change or release onto the production server all right so this is the end to the domain of continuous development let's go ahead and now talk about virtualization and containerization all right so let's start with the first question of this domain which says what is the difference between virtualization and containerization now this is a very important question guys because most of us get confused between virtualization and containerization so let's see what are the differences between these two things so virtualization is nothing but installing a new piece of operating system on top of a virtualized hardware what does that mean so basically there are Sophos like hypervisor or any of the software which specializes in virtualizing hardware so if you have a server which has around 64 gigs of ram and thousand TB of hard disk space with a software like hyper hypervisor what you can do is you can take that space and divide it among multiple operating systems right you can deploy multiple operating systems on the same hardware by virtualizing the hardware so as to the operating system will feel that say if you virtualized 1gb of ram from this whole system and say around 100 gb of storage the operating system will think that you know it only has one GB and hundred 1gb of RAM 100 GB of storage space available toward it cannot go beyond that reason being it does not know of the hardware which is beyond or which is which is ahead of the hypervisor software all right so in virtualization basically you have an hypervisor which is on top of your visit on top of your operating system and virtualizes the hardware beneath it right then you have a guest operating system so basically once your virtual is the hardware you install guest operating systems on top of that for example the best example for this would be VirtualBox right you install VirtualBox and then you can install operating systems on the VirtualBox with a given spec that you will decide and once you've installed the guest operating systems on top of that there would be the boundaries or the libraries that you probably would be downloading or that came with the operating system and on top of that you have the applications which would be running right so the key takeaway from virtualization should be that it's the whole operating system is installed from the kernel level to the application level everything is fresh everything is new now let's talk about containerization so the thing in containerization is that the host on top of host operating system you installed a software called the container engine now the container engine is just like any other software like you have an eye provider you have a container engine now the container engine does not encourage installing a whole operating system for example if you want to run a container for Ubuntu on say a Mac machine you can do that right it will basically in that container you will have basically the bare minimum libraries that amount to become the Ubuntu operating system - the canal right so in a container you do not have a kernel the kernel is always always used of the host operating system and this is the main difference between virtualization and containerization that in virtualization you have a separate kernel present of the virtual operating system but in containerization you do not have that and that is the reason that containers are very small they have the bare minimum libraries required for that container to behave as a particular operating system but the container itself does not contain any operating system it basically is based on the same kernel on which the host operating system resides all right and this is the basically the main difference between virtualization and containerization moving forward now the next question says without using docker that is without using docker to get into a container can we see the processes that are running inside the container of the docker container engine alright so this basically is relating to the same fact that if if you want to see the processes of a container which are running inside the docker container engine if you can see them from the outside basically that means that you know the processes are running in the same kernel of the host operating system right the processes that are running in the docker container engine would be basically as an addition to whatever is running on the host operating system as well and you can see that using the PS aux command right so for the host operating system it's just like any other software or any other process that it has to run but for the container it it basically thinks that it is running inside an operating system which it actually is not right so can you see the processes so the answer is yes you can see the processes which are running inside docker container and how can you see that how can you basically see these processes let me demonstrate it to you okay so we will we have come back to our AWS so let me clear up scream alright so as if I do docker PS right now you can see that there are no containers which are running on this system as of now now what I do is I run a container for open - so I'll do a docker run - I T and then I open D and then open - alright this ran a container for me and if I do dock appears now you can see that there's a container running which is basically of the ubuntu image so if I go inside this container now so I will do a docker exec - IT and then bash dr. Itzik - I T and then the sorry I forgot the container ID so the container ID and then - so if I do that I'm inside the container right and there's no process running inside this container as of now now if I were to duplicate this let me quickly again do an SSH so I'll do an SSH into the same server again so that I'm on Tolo okay great so if I do a PS aux these are all the processes which are running inside the operating system right now right but let us make it a little simpler what we can do is let me see all the processes which has the word watch in them right so let me make it more clear for you so these are the processes which have the watch keyword inside them okay so there are basically four processes which are running and which have the keyword voice inside of them now what I wanna do is inside this container I'm going to launch a watch process so what is that watch process that watch process is basically going to watch a particular command in a set interval of time and what is that command I basically want to say let's see the elders - L command okay so what is it doing it is keeping a watch on the command LS - L in every one second right you can see the time over here it is incrementing every second and basically it's keeping a watch on all these files which are there inside the container continuously okay now again so this is the dollar prompt that says we are outside the container right now now if I again do the same command that is again I search for processes which have the word watching it I can actually see that there is an new process which is running over here and this process is running inside the container which I'm able to see from the host operating system level right so the host operating system is doing is basically treating this particular process as if it was running on its own system that is the container and the host operating system because they are sharing the same kernel the host operating system is taking this process as if it was running inside of it right but if we if we look closely this basically this watch command is running inside the container right let me just quickly stop it you can see we are still inside the container and we have stopped the watch command and if I go here and if i refresh you can see that this voice command is again gone which was being mentioned over here before and this is exactly what we wanted we basically wanted to see a process which was running inside a container from outside the container that is from the host operating system and that is exactly what we just did alright so the question that without using docker can you see the processes that angle that are running inside a container so the answer is yes you can do it alright so the next question is what is the docker file used for what do you basically use a docker file form so a dock you file is nothing but it's a it's basically a text document to create a image using an older image and adding some files into it all right so this it's basically like a script that you run in Linux which can do all the things for you that are required for example I might need an Apache image and I want my website to be put inside the vert /ww slash HTML folder inside this particular Apache container now in order to do that if I were to do it without a docker file I would have to first download the Apache me so I would probably type docker run - ID - ID and then Apache once I have done that I will exec into the container and then go to the directory called Val www HTML probably I will do a git clone of the website that I want and then my website will be available in that container and hence I'll be able to use it right this is one way second way is I can create a docker file which would basically build this image for me without me having to do all these things all these manual things which I just told you all right so let's see how we can do that so let me just exit this container and let me remove the container which are just running inside my system right now okay but overtalk appears now it's clean you now what I want to do is I want to run this particular container or docker run - 90 - P I want to basically expose the port 83 to this containers port 80 and I want to run it as a demon so that it runs in the background and there is it okay so I have the container running which is this and what I want to do is I want to basically copy the website into this container so let me do a docker exact into this container - 90 this is the container ID and then container ID and then bash so I want to go inside this particular folder so if I do an LS over here you can see that there is an index or HTML and then an extra PHP which are running right so it's on exposed on port 83 which basically means if I go to a browser and if I quote with the source IP address on port 83 I should be able to see this Apache page and this is basically the container which I just ran over here okay what I want to do is inside this particular directory I would be basically copying the code of my website now let's see how we can do that so let me just exit this container let me do a drop called PS let me do top stop to this particular container so what would those two so basically if my Apache was running over here it should stop once I have stopped this container okay so it's stopped so if I do a refresh over here you can see the suicide can't be reached this is exactly what we want okay now let me do a git clone of my github and we get flown all right awesome now I'll go inside this folder and basically I want to copy this particular folder inside the container all right so for doing that let's contain let us create a docker file and what I want to say is in the image Sh har slash web app I want to add the folder DevOps IQ and where do I want to add it inside the container I want to add it in this particular directory okay this is where I'm gonna add it and inside DevOps IQ okay fair enough and that is it that is all you have to do I just come out of this editor and I'll now do a docker build of this talk of file with the name test so it says successfully built an image and it has been tagged as test great now if I'd run this image now docker run - I T - PC I run it on port 80 for run it as a daemon and run the image okay great so if I could port 80 for now let's see if the container is working first so yes the container is working now if I go inside DevOps IQ what do I see great so I can see the web so basically my website is now available inside the container by simply writing a docker file to do that and this is exactly what you wanted awesome guys so what is the docker file use for it is be we used for creating an image without having to do all the manual stuff of adding your files and everything all right now once this image of yours is ready you can push it to docker hub and anybody in the world can download it and can basically use your website on the local system great now the next question is explain container orchestration ok so fun so till now we have seen that you know we can deploy a container we can use it we can properly deploy an application on it and we can use it on the web browser right but it is not that simple when we talk about a website like Amazon or a website like Google right it has a lot of components with it for example on Amazon you would see that you have a comment section then on the home page you see that there are a lot of products which have the prices the ratings now each and every component the prices the ratings the name of the product the image of the product the comment section each and everything is basically a micro source it is a small part of an application which is running independently of all the other parts of the website right and all of this is possible using containers so basically what they would have done is they would have run each and every component inside a container now the problem over here is now when you have a website like Amazon you would be dealing like you will be dealing with minimum like 10 or 11 containers for one particular copy of that website or one particular instance of that website right now when you're dealing with ten eleven containers these containers have to be working in conjunction to each other they should be in sync with each other they should be able to communicate with each other right and they should also be able we should also be able to scale a particular container in in case it goes down for example the comment section container it goes down for some reason now if it goes down we have to keep a watch on it we have to redeploy it if it goes down and all of these activities which I just told you comes under container orchestration right if you were to manually deploy these containers on docker you will have to keep a manual check on all these containers but imagine when you have thousands or ten thousands of containers that you are dealing with in those kind of scenarios you need container orchestration now container orchestration can be done using various software so you have a software called cuban at ease and before that there was a software called docker swarm which was which basically made a life easier by doing all the manual work for us that is it will check the containers health it could scale them in case they become unhealthy they could always also notify you know the administrators by an email in case something happens right they can also run a monitoring software for you or average which basically gives you a report or the health status of all the containers which are running inside that software so this is what this is a very small part of what a container orchestration tool can do right and basically if you were to understand what container orchestration is is like I said when you work with multiple containers you have to take take in note a lot of things and that is possible using the container orchestration tools like humanities and docker swamp okay so the next question is what is the difference between Dorcas warm and cue manatees now they're both container orchestration tools we just saw that but why do we have to or if I were to choose between humanities and aqus warm which should I choose all right so let's look at the differences between each one of them so the first difference which is probably the most important difference or probably say is the deciding factor whether you know you should go ahead with this tool given that you have a short deadline and you have to deploy a project so installing docker swarm is very easy it comes prepackaged with the docker software so if you are installed dhoka dhoka swarm is already installed on your system you don't to worry about anything on the other hand installing cuban eighties is a very tough job right there are a lot of dependencies for cuban at ease you'll have to see the system you'll have to see the operating system on which it is running and a host of other things right it has a lot of dependencies and hence it is very tough to install but the moment you install it it becomes a very helpful that as humanities becomes very helpful because of the features that it offers which brings us to our second point docker swamp is faster than cuban it is reason being that it has less features than cuban ities and therefore making it a very light software and hence faster than cuban at ease so if you want to use docker swarm you should be reading about what dr. swarm does not offer and what cuban eighties offers and if you feel you do not need all the features that humanities is offering you can go ahead with daca swim and deploy your application in a faster manner but like I said Cuban ''tis it is is complex and has a lot of services and features because of which it is its deployments are a little slower when we compare it to Dorcas one third point which is most important point is dr. swarm does not give you the functionality of water scaling meaning if your containers go down or if your containers are basically performing at their peak capacity there is no option in Dhaka swamp to scale those containers on the other hand because of cuban ities monitoring services and the host of other features you have that option of providing auto scaling to your containers which basically means you can automatically scale the containers up and down as and when they are required and this is an amazing thing that cuban ''tis handles for us alright guys so these were the questions around the domain virtualization and containerization so moving ahead now our next domain is continuous integration so let's shed a light on what continuous integration is so our quests first question itself is what is continuous integration so continuous integration is basically a development practice or I'll say it's a stage which basically connects all the other stages of the DevOps lifecycle for example you you you push a code to get like we took an example and you push the code to get you might have provisions which might allow you that the the moment the code is pushed on to the remote repository it automatically gets deployed on the servers as well well if that is the case basically that would be possible using integration tools that would integrate your git repository with your remote server and that is exactly what Jenkins runs it's a continuous integration tool which helps you which helps us integrate different like devops lifecycle stages together so that they worked like an organism right this is what continuous integration means so because we discussed about what continuous integration is an expression says create a CI CD pipeline using Kalyan Jenkins to deploy a website on every commit on the main branch so on every push that you make to the remote repository the code should automatically get deployed on a remote server alright so this is something that we're gonna do just now all right but before going ahead let's see what is the architecture for this kind of a thing alright so this is how the whole thing is going to work basically the developer is going to commit the code to his github the github basically once it sees a change in the branch that we mentioned it is going to trigger Jenkins which in turn will integrate or will take the website from the github repository and push it on to the build server on which we want the website to be deployed all right sounds awesome great now let's go ahead and do this demo so for that we will have to ssh into our server so let us do that okay so i am in now let me clear the screen so first let's check if I Jenkins is running on this so so let me check the status for Jenkins so if I do a service Jenkins status I can see that the Jenkins service is active awesome so I'll just go here and I'll go to the Jenkins website which is basically available on 8080 alright so I'll enter my credentials and this is how the dashboard for Jenkins look like now our questioners or our aim is to create a job which basically will push a website that we are uploading to get up on a particular server all right so let's create a new job first so let's call our job as demo job ok and let's name it as a freestyle project and click OK so this will create a job in Jenkins for us all right so our job has now been created so what we want to do is I want to take code from my github so I'll have to specify the github repository over here ok and similarly I will have to say that I want to trigger the build the moment my anything is pushed on my remote repository alright and this should be it great so I mentioned that anything that is pushed on to my master should trigger a build on Jenkins okay and what should this build a what set of commands do I want to run once build is triggered so first I want to remove all the containers which are running inside my system so I'm going to clean up right so for that I say sudo doc RM hyphen F then add taller this basically is going to clean all the containers which are running currently in the system once this is done I want to build my website which is going or build my container which is going to have my website all right now how can we do that for that I'll have to push the code to my github which will have the docker file as well okay so we created a docker file inside you okay so here it is so we have the our docker file created in the DevOps IQ folder which was there in my home directory now what I want to do is I want to push so what is there inside this rocco file we saw that we could create a dock or file using if we write something like this in our dock file and this would basically create an image with our code which is there on github alright so what we'll do we'll just push this code to remote repository and let's add the message that we have ordered a taco fire crate and now let's push it to our remote repo great so it hasn't pushed to my remote repo and now if I just go here and check if my changes have been done or not let me just quickly refresh it so yes I have Dhaka file in my kit repository right now which was committed 42 seconds ago awesome great so now what I'll do is I'll come to my shangkun's and I will say that builders who docker build the docker file now where is that document the dock of I will basically be downloaded in the Jenkins wake workspace so that is in where lib Jenkins workspace and then name the job which is demo show up and that is it so inside this I will have my dhaka file and it will basically build it and name it as say Jenkins Jenkins it'll name it as Jenkins in the next step what I'll do I'll do a sudo docker run - IT and then - P and say I want to deploy it on 84 or say 87 port ok and what do I want to deploy I want to deploy Jenkins okay so this should do these this should basically do all the stuff so in the first command basically we are removing any container which is running on the system in the second command what we're gonna do is we're gonna build the docker file which is available in this workspace and this workspace will basically have my greater project and the link I have specified over here so it will basically just copy or it will pull the project and save it in the workspace of demo job so indeed sama job there is it aqua file so we are building this naka file and we are naming this created image as Jenkins and then we are running this image and exposing it to port 87 okay so let's save it awesome now what we have to do is I will have to go inside so if you want to configure a web hook the way to do that when I say a web book basically you want your github to interact with your champions whenever there is a push to a particular repository so in your repository go to settings and then go to web hooks so this is a web hook that I created for my Jenkins right so let me create it again for you so all you have to do is click on add web book right and enter the URL for your Jenkins over here so in my case it is this I'll just enter it over here followed by this keyword which is github - web hook and that is it once you specify that and just go down click on add web hook and this should basically send a request Jenkins and if everything goes well it will say last delivery was successful okay so any changes that I make to my github now should trigger a change over here now let me delete this job because I think even this job gets triggered when my github any changes made to my github right so let me delete this project okay great so I just have this job now awesome now let us see how it actually works so what I'm going to do is I come back to terminal do an LS and let me coincide DevOps IQ and let me do some changes in the cold so today I'll go into nano index.html so the first thing that I do is I change the title of the website so I called it as Jenkins test website okay and I change the image from two to one dot jpg and that is it let us see if I just push or if I just push this website onto my server what will happen so I do a git push sorry first I'd have to add these changed files into my repository git push origin master sorry get comment and let me label this commit as test push ok done now let's push this to a remote repository git push origin master and let's give the credentials awesome now if you wait here it should basically start a job so as you can see there is a job queued which is for demo job and this called automatically triggered by my github okay so let me refresh this okay so the moment it gives you a read that basically means that your job has been filled so let's see what has just happened why our job God failed so if you go here you can see the console output just like this okay so basically we is forward to add a sudo here and that is causing us a problem okay so we can fix this by just going down and editing a pseudo here save it and again we'll have to change the code let's call it us Jenkins test2 website we'll do a control XY and now let's add up files to our local repository get add now let's commit it test push - and now let's push this to our master I'll enter the credentials and this should be it okay so let's see so our second job got triggered automatically and it gives us a blue now blue means that your job was executed successfully so let's check what happened so we were deploying it on port 85 so let's check if it has been indeed deployed so it was on 485 and the folder was DevOps IQ okay so let's check I'm not sure if it was 485 let's check or the port that we have specified the port is 87 okay so let's go to port 87 okay so it's giving it a nursing unsafe port so for our troubleshooting let's check if the container is running so yes the container is running on port 87 but it says and unsafe port or what we can do is let us change it to say 82 and now let's just try to build the job from here we'll just click on bed now job has been completed and the port was 82 yes Apache is working now let's try going inside DevOps IQ folder and there you go you have your website with this title which you pushed on github now for one more time for testing purposes let us push our code once more and see what happens so I will say that this website is test 3 website and say the I change the image as well - 2 dot jpg okay save it do a git add to commit and say call it test which 3 and now let's hit push origin master enter the credentials great now let's check what will happen okay so our build has been started and it has been completed great so if i refresh just now it says Jenkins test3 website and the background also has been changed so congratulation guys we have successfully completed the demo so basically if you change anything in your github the website is automatically getting deployed on your build server right and on top of this just for making it more interesting what we can do is we can do a get log and we can revert on this commit that we saw earlier okay so let's do a git revert and then paste it agree to everything and then push to master and other credentials everything has been pushed job is getting triggered job is completed and if I go here again my website got reverted to a particular previous version awesome guys so we have completed the demo which basically asked us to create a CDC ICD pipeline using kit and Jenkins to deploy a website on every commit on the main branch so you've done it successfully awesome let's move on to our next domain which talks about configuration management and continuous monitoring awesome so what is configuration management and what is continuous monitoring let's understand it so what is the difference between ansible chef and puppet now before understanding the difference between ansible chef and puppet these are basically configuration management tools what is configuration management if you have say around 200 servers and you want to install a particular software on each of these servers what will you do but one way what you can do is you can basically go to each and every of these servers run a script and that basically will install software on that on the only source right the other way to do it is install a configuration management software using which you can deploy or you can install all these software's or you can control the configuration of these all these servers from one central place and that is exactly what configuration management means right now in configuration management you have many tools like ansible chef puppet etc but these are the three top tools which are used in the industry now the question is what is the difference between ansible chef and puppet alright so let's go ahead and see the differences all right so let's first talk about ansible so ansible is very easy to learn because it is based on Python so you don't have to sweat a lot or you don't have to sweat much on learning the commands for ansible because it is based in Python so if you know Python and symbol is going to be a cakewalk for you it is preferred for environments which are designed to scale rapidly basically with ansible the thing is that you don't have to install the ansible client software on top on the on the systems on which you want to basically deploy the configuration ansible just has to be installed on the master and that is it no other configuration required you can directly control the configuration of the client server given you have the access to it so it offers simplified orchestration reason being like I just told you that you don't have to worry about installing software's on the client machines ansible can stand alone or take care of all the complications that come forward when you are dealing with deploying configurations without installing a particular software on the client machines this is a basically a disadvantage of ansible that it has very underdeveloped GUI that is you only get the CLI to work with right and it has very limited features when we compare it with puppet and chef now let's talk about chef what how is chef different from ansible so it is Ruby based and hence it's difficult loss now Ruby is a language that not many people are acquainted with and hence people might find it difficult to get versed with the commands of Chef the initial setup is complicated when I compare it to the ansible the setup was very easy because I just had to install ansible on the host machine and on the client machine I didn't have to install any software so but with chef you have to do that and hence it becomes a little complicated but once all the setup and everything is done chef is very stable right it has it has been since it's a community product and it has been well contributed to it's a very stable product and it offers you resiliency so so of course if you when you are working on production servers probably working on chef would a better idea dan ansible because ansible does not have that has that create community when you compare it with chef and of course chef is the most flexible solutions for whis and middleware management now middleware basically means the software management part chef offers to be a great choice for configuration management reason being it can it is very reliable and is very mature because it was probably among the first configuration management tools to come out and because community has contributed a lot to this project it is very mature in its development stages as well now let us talk about puppet so puppet can be tough for people who are beginners in the DevOps world right because the it uses its own language called puppet DSL right the setup part is smooth when you compare it with chef but it's a little harder than ansible because when you're using puppet you use we use a master and an agent as well so you will have to install puppet agent on the client machine and only then puppet will be able to interact with the client software right now it has a strong support for automation so if you are planning to do some configuration management that you want to automate puppet is very compliant in that part you can easily do the automation part using puppet and it is not suitable for scaling any deployment so if you have say around 50 or 60 servers and you plan to add more in the future probably puppet would not be the right choice for that kind of an architecture it is good good to have when you have a stable infrastructure very probably not adding servers now and then but if you are working on cloud and you do not know the capacity that you would be running probably puppet would not be the good would not be a good idea to manage your configuration on your client okay our next question is what is the difference between asset management and configuration management so asset management basically deals with resources and deals with hardware which will have to plan so that our IT workforce can work with maximum efficiency right so we'll have to plan the planning of your Hardware of how many resources a particular team might need giving the right resources to the right people is what asset management counts in when we talk about configuration management it basically employs not the hardware but the software component of what all softwares are required by a particular employee of a team or a particular person in the team what's officer required by that person and for other person what software is required I mean rather than taking the radical approach of installing every software and every machine which should not be done because some software's are licensed so configuration management basically means installing the right software on the right system on which a particular person or on which a particular workload is going to run so our next question is what are n RPE plugins in nag yours okay so n RP plugins are basically extensions to Nagios which help you monitor the local resources of the client machines right so you don't have to SSH into the client machines to see how much of memory or how much of CPU is being used nanos being a monitoring tool you just have to install and the NRP extension on the client machine and it will give you a real-time data of the resources that are being consumed on that particular client machine and obviously when you are working in production environment you will be monitoring multiple machines and with the NRP plugins installed on each of those machines you can easily monitor the resources of them at one central place and that was exactly what NRP plugin is question is what are the difference between an active check and a passive check in Nagios okay so in a goose if the the data the monitoring log that you're getting from your clients if it's being delivered by an agarose agent in that case it is called an active check reason being nag use is actively involved in taking all the data or L or in collecting all the data from your clients but in case when you're dealing with systems wherein it does not allow you to install any other software or probably the software itself can generate monitoring logs in those cases what happens is rather than Nagios the software component pushes the logs to the Nagios master where it can take the logs and probably create a graph or create the metric for you in the dashboard so basically using those logs which are being published by some other software Nagios will create a report of the health monitoring part of your client systems right and that is why it is called a passive check reason being naggy osa is not involved on the client side at all it is basically the software's own services which are basically pushing the log to nag your master and hence it's called a passive check all right but if you talk about the architecture or the working or the life cycle of how this actually works between on the master itself the logs which are published are actually published to a queue right and whether it's an active check or a passive check the logs have to be published to that queue so that the Nagios master can pick them up and create the monitoring metric which is required all right so in a passive check and in a not active check the queue is going to be there but it's the only difference between the agents that is in an active check the Nagios agents are involved but in a passive check third party software tools are involved which publish the log to the Nagios master all right so our next question says create an answerable playbook to deploy Apache on a client server so basically we have to do configuration management so as to without I mean going inside the declined system we'll have to install a particular piece of software inside it okay so let me quickly do an ssh into my AWS machine and what i'm gonna do is i have a slave machine which i have already configured which can interact with my master that is if I do a ansible ping call you can see that there is a server one that has I have configured which has successfully responded to my Master's request okay now let me show you the server which is basically working so this is the server which is configured with my master right this is my client machine and on this machine I'll have to install Apache so if I right now go to the IP address of this machine it says connection refused reason being that there is nothing installed on this server or there is no Apache software installed on this particular server right now alright so let's install Apache now to do that you will have to write a playbook now what is the playbook a playbook looks something like this so it's basically a Yama file that you'll have to create so I have created one for me so where do you want to install the apache software is the part where you will have to specify an hosts so basically my my client machine is a part of a group called servers that i've created right so the hosts are servers and where can you actually specify what part is your machine or what which group is your machine a part of so that you can specify over here so it's in slash EDC slash ansible and slash host okay so as you can see over here this is the group name that is so us and inside servos have specified a server one client machine which has the IP address this so this is the IP address of my slave so if you can compare its 18.2 to 3 101 172 and if I compare it with my slave this is the IP address of my slave right and this has been configured over here so I can refer to my server 1 as servers or I can refer it to where's server 1 right so if I do let me do clear over here I can say ansible - em ping and I can say so one is where it will reach out to myself 1 or I can say service as well because it's part of the group service ok so this is how it works now I want to install Apache so for installing Apache I'll have to write a playbook which looks like this basically it's a yam L file so you start with the 3 dashed lines and then you specify hosts so host I've specified every sword every machine which is inside the server's group should install Apache on it right and what is the task I want to install Apache - this is basically a name you can specify anything over here then I've specified a PT basically I want to use the apt package to install Apache to the latest software ok now what I can will do I will type in ansible - playbook and I will type in Apache not Yammer I'll hit enter and now it has started to install everything so it has it is installing on the server's group it is gathering the facts and it saw that it is able to communicate with server 1 and now it is accomplishing the task of installing Apache alright so it has been done successfully so if I go to my Chrome browser now and if i refresh the address you can see that Apache is installed on this server automatically so I didn't have to basically SSH into the server it all happened automatically and if I had like five six computers which were running on which were running on AWS and if I wanted to install the software on it using Apache or using ansible this would have been the same way it's only that in the server group I would have specified more IP addresses which my ansible could talk to okay so this was tasks of basically deploying an answerable playbook on a client server without SSH doing an SSH into that client server and doing it from a central location right so this is done now let's move on to our next domain which is continuous testing now what is continuous testing so we talked about continuous development which is done using github we talked about continuous integration which is possible using Jenkins who talked about continuous configuration management which can be done using ansible and next online is we have continuous testing so once the code has been deployed it has been integrated with Jenkins it has been deployed on a server the next thing is automated testing that we discussed in the best practices before right and it can be done using a tool called selenium a software called selenium webdriver right so the first question is list out the technical challenges with selenium so the selenium tool is used widely for automatic testing or automated testing but what are the problems that you get with selenium so if you're using selenium mobile testing cannot be done so if you have developed an application for your mobile you cannot test it using selenium the reporting capabilities of selenium are very limited if there is if the if your application or your web application deals with pop-up windows or it gives pop-up windows selenium would not be able to recognize those pop-up windows and work on them Vibha oh and again selenium is only limited to web applications so if you have an application that probably runs on desktop probably it's a software that you have designed you cannot test that software using selenium selenium is only for those applications which can run inside a browser and if your if you want to check whether there is some image in your web page and that image - they have some particular content it is a little difficult to implement it in selenium all although it is not impossible it is possible you'll have to import some libraries and other things like that but natively selenium does not support image testing you'll have to work around will have to work around with selenium to import some libraries which could do it for you but like I said natively selenium does not support image testing so a next question is what is the difference between verify and assert commands so let us see the differences so if you're using assert in selenium if the command fails the whole execution comes to a halt whereas in verify it does not come to a halt it keeps on continuing the rest of the lines which are written in the code now why how can it be helpful how is it helpful to basically put execution at halt whenever there is an error which occurs for a particular line it is helpful when you're dealing with critical cases right for example if if there are five cases and say if case three fails case four and five cannot execute because they have a dependency on case three in those cases I would say that you would have to use assert with the case three but in in the same example if you talk about case one and case two they do not have a dependency or they do not create a dependency for any other test cases that have to run right for example case three case four case five are not dependent in case one in case two in those cases we can run the verify command which will not stop even if the the test case fails right and this basically is done to basically see what all is working and what all is not in one shot in our testing program and for those cases you would use verify but in the cases where you are testing critical cases and you do not want to waste your time testing other things if one of your case fails in those cases you will use the assert test so like I said it is used to validate critical functionality assert command and verify is used to very validate functionality which is of the normal behavior kind of kind of sinner which which comes into the normal behavior that that is it does not create a dependency for other things to not work because it stopped working all right so a next question is what is the difference between set speed and sleep methods so set speed is basically used for executing tasks at a particular interval that we specify for example say I want to echo hello world at intervals of 5 seconds in that case I can specify it using set speed but sleep method basically suspends the execution of the whole program for a particular interval for example if you're doing a selenium web test and the webpage takes around 3 seconds to load and you don't want testing to happen just after each line you can specify a sleep method of say around 3 seconds where it it waits for 3 seconds for the website to load and only then it will start executing the tests which follow that particular line right so this is the difference between set speed and sleep all right we hope you enjoyed this video on DevOps intimate and if you did please click on the like button and also click on the subscribe button and be like and to never miss out on any updates from us we'll be coming with more videos soon so if you have any more queries guys you can put it down in the comment section and we'd be happy to answer all your queries I'll see you in some other video guys have a great day ahead and good bye

Channel: Intellipaat

Views: 18,393

Rating: 4.9196429 out of 5

Keywords: devops interview questions and answers, devops interview questions, git interview questions and answers, devops engineer interview questions, devops engineer interview, git interview questions, puppet interview questions, jenkins interview questions, docker interview questions, devops interview, interview questions on devops, chef interview questions, ansible interview questions, devops training, devops, devops intellipaat, intellipaat

Id: oG8I8kds8rI

Length: 82min 39sec (4959 seconds)

Published: Sun Jul 05 2020