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Introduction to Docker Containers - Docker Captain
This document provides an introduction to Docker. It begins with an overview of the shift from monolithic to microservices architecture and how Docker addresses the complexity problems that arise. Docker is described as a tool that packages applications and dependencies into standardized units called containers that can run on any Linux server. Key differences between Docker containers and traditional virtual machines are outlined. The document then covers Docker concepts like images, containers, and the Docker Engine. It demonstrates the Docker build, ship, and run workflow and introduces common Docker commands and tools.
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Introduction to Docker Containers - Docker Captain
- 1. Introduction to Docker AjeetSingh Raina Docker Captain – Docker, Inc.
- 2. 2 Who Am I? •Sr. Systems Development Engineer at DellEMC • 1st half of my career was in CGI & VMware • 2nd half of my career has been in System Integration • Testing/Project Lead for Dell EMC. • Definitely more IT pro than developer • @ajeetsraina (a frequent Twitterati) http://www.collabnix.com
- 3. Agenda - A Shiftfrom Monolithic to Microservices Architecture - What is Docker? What problem does it solve for us? - How Docker is different from VM & CM - Using Docker: Build, Ship and Run WorkFlow - Docker Ecosystem & Native Offering - Docker Tools - Demo
- 4. A Shift fromMonolithic to Microservice Architecture
- 5. 5 Monolithic A DecadeAgo (and still valid) Ap - Apps were monolithic Slow Changing - Built on a single stack such as .NET or Java - Long Lived - Deployed to a single server Big Server
- 6. 6 Today - Apps areconstantly developed - Newer version are deployed often - Built from loosely coupled components - Deployed to a multitude of servers Customer/ Clients/ Users Data Storage Data Storage Data Storage
- 7. 7 Once upon atime… A Software Stack
- 8. 8 Now....much more distributed,complex..
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- 11. 11 An Effort tosolve the problem complexity…
- 12. 12 Every possible goodsto ship X Every possible way to ship
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- 14. 14 Docker ~ Bringsstandardization on packaging goods
- 15. 15 What is Docker? VirtualizationTool? Configuration Manager? VM Manager?
- 16. 16 Less Portable, Minimal Overhead MostPortable, Lots of Overhead Manual Configuration Traditional VMs Configuration Tools
- 17. 17 Less Portable, Minimal Overhead MostPortable, Lots of Overhead Manual Configuration Traditional VMs Configuration Tools
- 18. Traditional Software DevelopmentWorkflow (Without Docker)
- 28. 28 What is Docker? A Company as well as Product Developed by DotCloud Inc. ( Currently Docker Inc.) A Framework they built their PaaS upon. Released it as open source 4+ years back Cross-platform nature and friendliness towards System Admin and Developers • Developers - concentrate on building applications and getting them running inside the containers • System Admins - work on running the containers in deployment. Possible to set up in any OS, be it Windows, OSX, Linux - It work the same way Guaranteed to run the same way - Your development desktop, a bare-metal server, virtual machine, data center, or cloud
- 29. 29 What is Docker? •A tool that can package an application and its dependencies in a virtual container. • Implementation of a container which is portable using a concept of image • Docker uses host OS kernel, there is no custom or additional kernel inside container. All containers runs on machine are sharing this "host" kernel. • Docker uses resource isolation features of the Linux kernel such as cgroups and kernel namespaces to allow independent "containers" to run within a single Linux instance, avoiding the overhead of starting virtual machines.
- 30. 30 What is Docker? •Standardized packaging for software and dependencies • Isolate apps from each other • Share the same OS kernel • Works for all major Linux distributions • Containers native to Windows Server 2016
- 31. Docker containers areNOT VMs
- 32. 32 Docker containers areNOT VMs • It’s not quite like a VM • Uses the host kernel • Can’t boot a different OS • Can’t have its own modules • Doesn’t need init as PID 1 • Doesn’t need syslogd, cron. It’s just a normal process on the host machine • Contrast with VMs which are opaque
- 33. 33 VM Vs Docker- Similarity Virtual Machines Docker Process in one VM can’t see processes in other VMs Process in one container can’t see processes in other container Each VM has its own root filesystem Each container has its own root file system(Not Kernel) Each VM gets its own virtual network adapter Docker can get virtual network adapter. It can have separate IP and ports VM is a running instance of physical files(.VMX and .VMDK) Docker containers are running instances of Docker Image Host OS can be different from guest OS Host OS can be different from Container OS
- 34. 34 VM Vs Docker- Difference Virtual Machines Docker Each VM runs its own OS All containers share the same Kernel of the host Boot up time is in minutes Containers instantiate in seconds VMs snapshots are used sparingly Images are built incrementally on top of another like layers. Lots of images/snapshots Not effective diffs. Not version controlled Images can be diffed and can be version controlled. Dockerhub is like GITHUB Cannot run more than couple of VMs on an average laptop Can run many Docker containers in a laptop. Only one VM can be started from one set of VMX and VMDK files Multiple Docker containers can be started from one Docker image
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- 38. Docker + WindowsServer = Windows Containers Native Windows containers powered by Docker Engine Windows kernel engineered with new primitives to support containers Deep integration with 2+ years of engineering collaboration in Docker Engine and Windows Server Microsoft is top 5 Docker open source project contributor and a Docker maintainer Infrastructure Windows Server 2016 Bins/Libs App Docker Engine Bins/Libs App Bins/Libs App
- 39. 39 They’re different, notmutually exclusive
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- 41. 41 Some Docker vocabulary DockerImage The basis of a Docker container. Represents a full application Docker Container The standard unit in which the application service resides and executes Docker Engine Creates, ships and runs Docker containers deployable on a physical or virtual, host locally, in a datacenter or cloud service provider Registry Service (Docker Hub or Docker Trusted Registry) Cloud or server based storage and distribution service for your images
- 42. Image Layering -An application sandbox. - Each container is based on an image that holds necessary config data. - When you launch a container from an image, a writable layer is added on top of this image - An image that has no parent. - Platform images define the runtime environment, packages and utilities necessary for containerized application to run. - A static snapshot of the containers' configuration. - Image is a read-only layer that is never modified, all changes are made in top-most writable layer, and can be saved only by creating a new image. - Each image depends on one or more parent images
- 43. Basic Docker Commands PullingDocker Image $ docker pull ajeetraina/catweb Listing out Docker Images $ docker image ls Running Docker Containers $ docker container run –d –p 5000:5000 –-name catweb ajeetraina/catweb Stopping the container $ docker container stop catweb (or <container id>)
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- 47. 48 Put it alltogether: Build, Ship, Run Workflow Developers IT Operations BUILD Development Environments SHIP Create & Store Images RUN Deploy, Manage, Scale
- 48. Docker on LinuxVs Windows
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- 51. Dockerfile – WindowsExample Dockerfile – Linux Example
- 52. Docker Compose –Building Microservices in easy way Backend Service Frontend Service Environmental variables Environmental variables Specify Volumes/Network Specify Volumes/Network
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- 54. References www.collabnix.com www.play-with-docker.com – DockerPlayground ( For Test Drive) www.docs.docker.com
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