Top 25 Docker Interview Questions and Answers for 2024

hi guys welcome to this video on dockerinterview questions and answersdocker is a popular devops tool used toautomate the deployment of applicationsin lightweight containers so thatapplications can work efficiently indifferent environmentsdocker was initially released in 2013and since then has become the go tosolution for containerizationin this video we have compiled the mostimportant docker interview questionsthat you might face in a docker ordevops interviewso without further ado let's get startedso let's go through and you're going tobe asked to explain what thearchitecture of docker is and dockerreally is the most popularcontainerization environment so dockeruses a client server architecture andthe docker client is a service whichruns in a command line and then thedocker daemon which is run as a rest apiand within the command line will acceptthe requests and interacts with theoperating system in order to build thedocker images and run the dockercontainers and then the docker image isa template of instructions which is usedto create containers the dockercontainer is an executable package ofapplications and its dependenciestogether and then finally the dockerregistry is a service to host anddistribute docker images among otherusers so you'll also be asked to providewhat are the advantages of docker overvirtual machine and and this issomething that comes up veryconsistently in fact um you may want toeven extend it as having what are thedifferences between having a dedicatedmachine a virtual machine and a dockeror docker-like environment and reallythe the arguments for docker are justabsolutely fantastic you know first ofall docker does contain and occupydocket containers occupy significantlyless space than a virtual machine or adedicated machine the boot up time ondocker is significantly faster than a vmcontainers have a much betterperformance as they are hosted in asingle docker image docker is highlyefficient and very easy to scaleparticularly when you start working withkubernetes easily portable acrossmultiple platforms and then finally forspace allocation uh docker data volumescan be shared and reused among multiplecontainers the argument against virtualmachines is significant and particularlyif you're going into an olderenvironment where a company is stillusing actual dedicated hardware andhaven't moved to a cloud or cloud-likeenvironment your arguments for dockerare going to be very very persuasive bevery clear on what the advantages arefor docker over a virtual machinebecause you want to be able tosuccinctly share them with your team andthis is something that's important whenyou're going through the interviewprocess but also equally importantparticularly if you're working with acompany that's transitioning or goingthrough a digital transformation wherethey aren't used to working with thetools like docker you need to be able toeffectively share with that team whatthe benefits are so how do we sharedocker containers with different nodesand in this instance what you want to beable to do is leverage the power ofdocker swarm so docker swarm is a toolwhich allows the i.t administrators anddevelopers to create and manage clustersof swarm nodes within the dockerplatform and there are two elements tothe node there's the manager node andthen there's the the worker node themanager node as you'd assume manages theentire infrastructure and the workingnode is actually the work of the agentas it gets executed so what are thecommands to create a docker swarm and sohere we have an example of what amanager node would look like and onceyou've created a swarm on your managernode you can now add worker nodes tothat swarm and again when you'restepping through this process be veryprecise in the execution part that needsto be taken to be able to effectivelycreate a swarm so start with the managernode and then you create a worker nodeand then finally when a node isinitialized as a manager node it canimmediately create a token and thattoken is used for the worker nodes andassociating the ip address with theworker nodes question 17 how to runmultiple containers using a singleservice it is possible to run multiplecontainers a single service by usingdocker compose and docker compose willactually run each of the services inisolation so that they can interact witheach other the language used to writeout the composed files that allow you torun the service is called yaml and yamosstands for yet another markup languageso what is the use of a docker file so adocker file actually is used forcreating docker images using the buildcommand so let's go through and show onthe screen what that would look like andthis would be an opportunity where ifyou're actually in a technical interviewyou could potentially even ask hey can idraw on a whiteboard and show you whatthe architecture for using the buildcommand would look like and what theprocess would look like um again whenyou're going through an interviewprocess as someone who interviews a lotof people one of the things i reallylike is when an interview candidate doessomething that's slightly different andin this instance this is a great exampleof where you can stand up to thewhiteboard and actually show what canactually be done through actuallycreating images on the whiteboard veryquickly little square boxes where youcan actually show the flow for creatinga build environment as an architect thisshould be something that you'recomfortable doing and by doing it in theinterview and certainly you want to askpermission before you actually do it butdoing this in the interview really helpsdemonstrate your comfortable feelings ofworking with these kind of architecturedrawings so back to the question ofcreating a docker file so we go throughand we have a docker file that actuallythen goes ahead and creates the dockerimage which then in turns creates thedocker container and then we are able topush that out up to a docker hub andthen share that docker hub witheverybody else as part of the dockerregistry with the whole network so whatare the differences between docker imageand docker containers so let's gothrough the docker image so the dockerimages are templates of a dockercontainer an image is built using adocker file and it stores that dockerfile in a docker repository or a dockerhub and you can use docker hub as anexample and the image layer is a readonly file system the docker container isa collection of the runtime instances ofa docker image and the containers arecreated using docker images and they arestored in the docker daemon and everycontainer is a layer is a read writefile system so you can't replace theinformation you can only append to itso while you can actually use yamo orwriting your so a question you can beasked is instead of yammer what can bean alternate file to build dockercompose so yaml is the one that is thedefault but you can also use json so ifyou are comfortable working with jasonand my that is something that you shouldget comfortable with is you want to beable to use that to name your files andas a frame reference json is a logicalway of being able to do value pairedmatching using a javascript like syntaxso you're going to be asked to how tocreate a docker container so let's gothrough what that would look and we'llbreak it down task by task so the taskis going to be create a mysql dockercontainer so to do that you want to beable to build a docker image or pullfrom an existing docker image from adocker repository or hub and then youwant to be able to then use docker tocreate a new container which has mysequel from the existing docker imagesimultaneouslythe layer of read write file system isalso created on top of that image andbelow at the bottom of the screen wehave what the commands lines look forthat so what is the difference between aregistry and a repository so let's gothrough that so for the docker registryand repository for the registry we havea docker registry is an open sourceserver-side service used for hosting anddistributing docker images whereas incontrast for repositories a collectionof multiple versions of a docker imagein a registry a user can distinguishbetween docker images with their tagnames and then finally on the registrydocker also has its own default retreatcalled docker hub for the repository itis a collection of multiple versions ofdocker images it is stored in a dockerregistry and it has two types of publicand private registry so you can actuallycreate your own enterprise registry soyou're gonna be asked you know what arethe cloud platforms that support dockerreally you know lists them all and wehave listed here amazon web servicesmicrosoft azure google cloud rackspacebut you could add in their ibm bluemixcould put in red hat really any of thecloud service providers out there todaydo support docker it's just become anindustry standard so what is the purposeof expose and publish commands in dockerso if we go through expose is aninstruction used in docker file whereaspublish is used in docker run commandfor expose it is used to expose portswithin a docker network whereas withpublish it can be used outside of adocker environment for expose it is adocumenting instruction used at the timeof building an image and running acontainer whereas with published is usedas to map a host port to a runningcontainer port for expose is the commandused in docker whereas for publish weuse the command-p for when we're doingour command line used in docker andexamples of these are expose 8080 orwith docker we would put in or forpublish we'd do the example docker rund dash p and then 0.0.0.80a colon 80 as our command line with thatwe have reached the end of this dockerinterview questions videoi hope you enjoyed this video do likeand share it thank you for watching andstay tuned for more from simply learnhi there if you like this videosubscribe to the simply learn youtubechannel and click here to watch similarvideos to nerd up and get certifiedclick here