Docker engine is the part of Docker which creates and runs Docker containers. A Docker container is a live running instance of a Docker is a file you have created to run a specific service or program in a particular OS. So for example say I want a web proxy; I can create a Docker but it's just a file. To use it I need to create a Docker container which uses that file to be a live running sq VM with the config of my choice. Docker engine (or just Docker) is the program which creates and runs the Docker container from the Docker image file.
What is Docker? Please explain it in simple terms.
NOTE If you are interested in starting with Docker and container please check out my Medium blog How to Start With Container Using Docker s@bryantjiminson You Let say you need to build an application. That can be next Facebook next Pandora next Amazon next Youtube or whatever. To make that application to be available to the public you need some place to host it. Previously that means you need to build your ownputer and setup a dedicated web service called server which is basically aputer dedicated for hosting website or web service instead for your own personputer or put that application onto hostingpany like 1&1 Geocity etc. Then the age of cloud came in. Apany like Amazon became very good at putting your application through their own data center which is a bunch of collections of servers. Unlike web hosting service thesepanies adopted a concept called virtualization meaning that the hardware resources can be broken down even further through software functionality and provide resources more optimally to customers who need them. This is why cloudputing is known as utilityputing since you only pay for the services you use instead of taking the entire server for your own use. This is generally more cost efficient for both yourself and for the hostingpany not to mention it is more optimized for performance. But even traditional cloudputing cannot avoid one thing heavy operating system usage. When I mean operating system I mean like Microsoft Windows Linux (RHEL Ubuntu Fedora etc) or MacOS. These OSes are huuuuge. When you download them they can easily go over 1 gigabytes in size also known as OS s 434 77 master_ s zoomable faster process faster and do many things faster. As you learn further you will learn why docker is a good addition to something called microservices but that is entirely a different beast topic.
What are the popular Docker interview questions?
Are you planning for a Docker interview? Then going through these top Docker interview questions italic is a must. It a well-known fact that Docker is replacing Vms. So be prepared to answer a few questions on Docker in your next interview. This answer has a bunch of interview questions from basic to an expert level that an interviewer could ask. Let get started!! Ex the architecture of Docker Command to list down the running containers Docker ps ordered-list 1. What are the Cloud platforms that support Docker? Below are the Cloud platforms that Docker runs on Amazon Web Services Microsoft Azure Google Cloud Platform Rackspace Hope this helps!
How is Kubernetes (k8s) different from Docker?
Comparison of the Two Big Cloud Giants Why we choose Kubernetes? A couple of months ago I set out to investigate some orchestration tools for Docker containers. I.e. something that would help us schedule Docker containers onto nodes in a cluster and make sure that our services stays up in case of various failures. But let start at the beginning why would we need this in the first place? Prior Setup We had a somewhat decent setup even before we moved to Kubernetes. For example we were using continuous delivery for every service from Jenkins so that on eachmit we would run our tests and integration tests (in Docker) generate an artifact build a Docker to a production server. An open source framework would also be nice since it would allow us to keep an eye on the progress of the project and report issues etc. Also if the current backer(s) bail out someone else might continue working on the project. It would also be of interest if the framework provided multi-cloud capabilities. Both in the sense that it would be able to get it up and running on various different cloud provides to avoid lock-in but also to potentially schedule containers to different clouds (if configured to do so). Another thing we suffered from previously was service discovery. Thus we wanted it to be easy to reach out to other internal services in our cluster without changing the application code. And lastly we would prefer a managed framework as a service option so that we can keep the hassle of setting up and maintaining it to a minimum. Finding a Framework I set out to investigate a couple of different alternatives that I found interesting and these were the ones I looked into AWS ECS Docker Swarm s Mesosphere DCOS s Tutum s Kubernetes Docker Swarm Docker Swarm is the native clustering for option Docker. Because Docker Swarm serves the standard Docker API any tool that alreadymunicates with a Docker daemon can use Swarm to transparently scale to multiple hosts. The latter sounded really great (easy) for us since we were already using dockerpose code to start our services. It also meant that we didn need to learn much new. We already knew Docker and Swarm uses the standard Docker APIs. But by the time we looked into Docker Swarm it had not yet reached 1.. This was the main reason for not picking Docker Swarm. But there were other things as well that were a bit tedious. For example while Swarm supports a wide variety of service discovery s engines I heard from an ex-colleague that setting this up and more importantly having it stay up could be a bit of a hassle. I.e. Docker Swarm is not a managed service so we would have to make sure that it working and is up and running by ourselves. Rolling updates didn turn out to be as easy as in some of the other alternatives we tried. At least back then doing a rolling update of containers in Swarm was something that you had to implement yourself. For example by setting up Nginx as a load balancer infront of a group of containers. At this time there was also some worries that the design of Swarm might be flawed. Thanks A2A.
What are some tips, tricks and gotchas when using Amazon ECS?
Wrong Docker Registry Path I found that if I create an ECS Task with a wrong Docker registry path the Service tries to create the Task fails and loops. The problem is not visible in the Service but in the stopped Task which shows STOPPED CannotPullContainerError API error (44) manifest for host not found code This doesn stop a CloudFormation deploy that contains this wrong Task. The ECS cluster is running but doesn report back to CloudFormation that it deployed successfully. After two hours the CloudFormation deploy fails with Service arnawsecsap-southeast-2accountservice did not stabilize. code CloudFormation Stuck in UPDATE_ROLLBACK_IN_PROGRESS When a CloudFormation deploy failed because of a mistake I made - the ALB URL did not match the URL in the app after I changed it - it looked like CloudFormation and ECS had trouble stabilising. My tasks were being stopped and restarted in a loop. It only proceeded with the rollback when I deleted the ECS cluster.
How do you use Docker as a VM?
Everyone repeat along with me. Docker is NOT a VM . Don treat docker containers like a vm youll be shooting yourself in the foot on down the road. With docker you should really be focused on using it to deploy single applications in a containerized fashion. It helpful for making an application easy to deploy and manage from an operations standpoint. Say if you have a web server like apache it would be really easy to setup all your configs and whatnot inside of a docker container and deploy the service onto any system without having to worry about all of the dependencies and operating system configurations. This makes it easily portable. So with one simplemand you can deploy a web server without worrying about Is this centos or ubuntu do I need to deploy it to or to Do I need to use systemd to manage it or init? Im generally really bad with analogies but Ill give it a shot Think of your total system as a house with rooms in them each room serves a purpose but they all rely on the houses utilities such as electricity water and cable tv. When you have a hypervisor that running VM inside of it it more like a large building with multiple apartments in it each apartment has it own electricity water and cable tv. A VM is kind of similar to this it a pre-allocated unit inside of your server with resources allocated to it but it is it own little ecosystem. Docker on the other hand is more like saying youve got a box in your room that has your entertainment system in it it using the electricity from your house and so on but it not in any way a discrete system unto itself. So you could say take your entertainment system and move it over to your neighbors house easily and just plug it into their utilities. It just a convenient way to package things up.
What is the difference between the Docker Engine and Docker Daemon?
Let me first start with the basics first. We know that Docker is a tool which is used to automate the deployment of applications in lightweight containers so that applications can work efficiently in different environments. Now moving further many of us want to know what is the Docker engine and Daemon and the difference between them. Below is the architecture of Docker Docker engine Docker engine or Docker is a client server application that builds and executes containers using Dockerponents REST API is a primary mode ofmunication between Docker Client and Docker Daemon Docker toolbox is used for older Windows and Mac systems with the following features Docker daemon Docker Daemon is a server which interacts with the operating system and performs all kind of services The Docker Daemon listens for REST API request and performs the operation Amand dockerd is used to start a Docker Daemon Docker Host runs the Docker Daemon and Registry Now the important question is what is the difference between Docker daemon and docker engine Docker Daemon checks the client request andmunicates with the Dockerponents in order to perform a service whereas Docker Engine or Docker is the base engine installed on your host machine to build and run containers using Dockerponents and services In case you wanna learn more watch the below video s Happy learning!
What are some tools to deploy and manage docker instances?
First Docker core platform consist of variety of products and services Docker Engine (Docker Deamon)n Docker Hub (Registry)n Docker Machine (Host provisioning)n Docker Swarm (Host clustring)n Docker Compose (Container Orchestration)n Docker Orca (Application Management)n Kitematic (GUI) Apart from these there are many other tools which provideplete framework Provisioning Networking APIs Orchestration Countinous Integration Delivery(CI) load balancing etc. Also they are using cloned sheep architecture(not all but soon everyone will going to use). Codeship 's Docker Infrastructure the new way to run your tests on Codeship. Full Customizability Easily mirrior your Development Test and Production Environments with full parity. It allows for the customized definition of the running environment. Tutum Docker platform for Dev & Ops nWith collabration with docker Tutum team will continue working on our shared vision and building technology to run any code on any server is rmended by docker. The Ultimate and best tool for Docker. Googles Kubernets Project Panamax Docker management for Humans nAn open-source project that makes deployingplex containerized apps as easy as Drag-and-Drop. It provides friendly interface for users of Docker Fleet & CoreOS. With panamax you can easily create share & deploy any application no matter howplex it can be. Basically for the multi-contaienr application this is best solution. 3scale allows the serviceposition orchestration to manage loosely coupled stacks of micro-services. This stack of API management infrastructure integrates with any containerized driven architecture as AWS Google Rackspace etc. TreeScale is also better. It allows private docker registry with unique build system and fast network discovery. They claimed with using unique build process it is building images 45% faster than standard docker engine. This is amazing and fascinating a lot. Koding is a robust and feature rich cloud-based development environment Jenkins Cluster DockerUI nWhile most devs and admins create and run Docker containers via themand line Docker Remote API enables them to run the samemands through a RESTful API. Enter DockerUI. This Web front end allows you to handle many tasks normally managed from themand line of a Web browser. All of the containers on a given host can be manipulated via a single connection and the project has almost no dependencies. It is however under heavy development but it MIT-licensed so it can be reused quite freely. Which means you actualy does not require any special tool for docker. But it's tidious to do all the things manuaally. In addition it contains no built-in authentication or security so be sure to put any publicly exposed DockerUI connections behind something with a password on it. Still there are many more tools for docker. Based on your requirment functioning parameters cluster setting dependencies and other factors you have to choose the perfect tools for your project.