Docker (software)

This article is about the virtualization software. For the desktop icon docker, see Dock (computing). For company, see Docker, Inc. For other uses, see Docker (disambiguation).
Docker
Original author(s) Solomon Hykes
Developer(s) Docker, Inc.
Initial release 13 March 2013 (2013-03-13)
Stable release
1.12.2[1] / 11 October 2016 (2016-10-11)
Repository github.com/docker/docker
Written in Go[2]
Operating system Linux[lower-alpha 1]
Platform x86-64, ARM (experimental) with modern Linux kernel
Type Operating-system-level virtualization
License Apache License 2.0
Website www.docker.com

Docker is an open-source project that automates the deployment of Linux applications inside software containers. Quote of features from Docker web pages:

Docker containers wrap up a piece of software in a complete filesystem that contains everything it needs to run: code, runtime, system tools, system libraries – anything you can install on a server. This guarantees that it will always run the same, regardless of the environment it is running in.[5]

Docker provides an additional layer of abstraction and automation of operating-system-level virtualization on Linux.[6] Docker uses the resource isolation features of the Linux kernel such as cgroups and kernel namespaces, and a union-capable file system such as aufs and others[7] to allow independent "containers" to run within a single Linux instance, avoiding the overhead of starting and maintaining virtual machines.[8]

The Linux kernel's support for namespaces mostly[9] isolates an application's view of the operating environment, including process trees, network, user IDs and mounted file systems, while the kernel's cgroups provide resource limiting, including the CPU, memory, block I/O and network. Since version 0.9, Docker includes the libcontainer library as its own way to directly use virtualization facilities provided by the Linux kernel, in addition to using abstracted virtualization interfaces via libvirt, LXC (Linux Containers) and systemd-nspawn.[10][11][12]

Healthchecks

A Healthcheck instruction tells Docker how to test if a container is still working, and in version 1.12.1, you’ll find a new Healthcheck Dockerfile instruction to support user-defined healthchecks. So now we’re able to define what exactly healthy containers means for us, and check them accordingly.

Using this feature will allow us to discover various cases we might have overlooked before, such as a server process that’s still running, but is unable to handle new connections.

This feature works along with the Swarm feature, and in case one of our containers is marked as unhealthy, the problem will be handled for us and a replica container will arise.

Overview

Docker can use different interfaces to access virtualization features of the Linux kernel.[12]

As actions are done to a Docker base image, union file system layers are created and documented, such that each layer fully describes how to recreate an action. This strategy enables Docker's lightweight images, as only layer updates need to be propagated (compared to full VMs, for example).

According to industry analyst firm 451 Research, "Docker is a tool that can package an application and its dependencies in a virtual container that can run on any Linux server. This helps enable flexibility and portability on where the application can run, whether on premises, public cloud, private cloud, bare metal, etc."[13]

Docker implements a high-level API to provide lightweight containers that run processes in isolation.[14]

Building on top of facilities provided by the Linux kernel (primarily cgroups and namespaces), a Docker container, unlike a virtual machine, does not require or include a separate operating system.[13] Instead, it relies on the kernel's functionality and uses resource isolation (CPU, memory, block I/O, network, etc.) and separate namespaces to isolate the application's view of the operating system. Docker accesses the Linux kernel's virtualization features either directly using the libcontainer library, which is available as of Docker 0.9, or indirectly via libvirt, LXC (Linux Containers) or systemd-nspawn.[12][15]

Because Docker containers are so lightweight, a single server or virtual machine can run several containers simultaneously. A 2016 analysis found that a typical Docker use case involves running five containers per host, but that many organizations run 10 or more.[16]

By using containers, resources can be isolated, services restricted, and processes provisioned to have an almost completely private view of the operating system with their own process ID space, file system structure, and network interfaces. Multiple containers share the same kernel, but each container can be constrained to only use a defined amount of resources such as CPU, memory and I/O.

Using Docker to create and manage containers may simplify the creation of highly distributed systems by allowing multiple applications, worker tasks and other processes to run autonomously on a single physical machine or across multiple virtual machines. This allows the deployment of nodes to be performed as the resources become available or when more nodes are needed, allowing a platform as a service (PaaS)-style of deployment and scaling for systems like Apache Cassandra, MongoDB or Riak. Docker also simplifies the creation and operation of task or workload queues and other distributed systems.[17][18]

Integration

Docker can be integrated into various infrastructure tools, including Amazon Web Services,[19] Ansible,[20] CFEngine,[21] Chef,[22] Google Cloud Platform,[23] IBM Bluemix,[24] Jelastic,[25] Jenkins,[26] Microsoft Azure,[27] OpenStack Nova,[28] OpenSVC,[29] HPE Helion Stackato, Puppet,[30] Salt,[31] Vagrant,[32] and VMware vSphere Integrated Containers.[33][34]

The Cloud Foundry Diego project integrates Docker into the Cloud Foundry PaaS.[35]

Red Hat's OpenShift PaaS integrates Docker and related project (Kubernetes, Geard, Project Atomic and others) since v3 (June 2015).[36]

The Apprenda PaaS integrates Docker containers in version 6.0 of its product.[37]

History

Solomon Hykes started Docker in France as an internal project within dotCloud, a platform-as-a-service company,[38] with initial contributions by other dotCloud engineers including Andrea Luzzardi and Francois-Xavier Bourlet. Jeff Lindsay also became involved as an independent collaborator. Docker represents an evolution of dotCloud's proprietary technology, which is itself built on earlier open-source projects such as Cloudlets.

Docker was released as open source in March 2013.[14] On March 13, 2014, with the release of version 0.9, Docker dropped LXC as the default execution environment and replaced it with its own libcontainer library written in the Go programming language.[10][15] As of October 24, 2015, the project had over 25,600 GitHub stars (making it the 20th most-starred GitHub project), over 6,800 forks, and nearly 1,100 contributors.[39]

A May 2016 analysis showed the following organizations as main contributors to Docker: The Docker team, Cisco, Google, Huawei, IBM, Microsoft, and Red Hat.[40]

Collaboration

See also

Notes

  1. ↑ Docker on non-Linux platforms uses a Linux virtual machine to run the containers.[3][4]

References

  1. ↑ "Docker Changelog". docs.docker.com. Docker, Inc. 2016-10-11. Retrieved 2016-10-13.
  2. ↑ "Docker source code". docs.docker.com. Docker, Inc. 2015-10-12. Retrieved 2015-10-24.
  3. ↑ https://docs.docker.com/installation/windows/#virtual
  4. ↑ https://docs.docker.com/installation/mac/#VM
  5. ↑ https://www.docker.com/what-docker
  6. ↑ O'Gara, Maureen (26 July 2013). "Ben Golub, Who Sold Gluster to Red Hat, Now Running dotCloud". SYS-CON Media. Retrieved 2013-08-09.
  7. ↑ "docker/docker". GitHub. Retrieved 2015-12-29.
  8. ↑ "Docker Documentation: Kernel Requirements". docker.readthedocs.org. 2014-01-04. Archived from the original on 2014-08-21. Retrieved 2014-08-20.
  9. ↑ Dan Walsh. "Yet Another Reason Containers Don't Contain: Kernel Keyrings". projectatomic.io. Retrieved 13 April 2015.
  10. 1 2 Steven J. Vaughan-Nichols (2014-06-11). "Docker libcontainer unifies Linux container powers". ZDNet. Retrieved 2014-07-30.
  11. ↑ "libcontainer - reference implementation for containers". github.com. Retrieved 2014-07-30.
  12. 1 2 3 "Docker 0.9: Introducing execution drivers and libcontainer". docker.com. 2014-03-10. Retrieved 2015-01-20.
  13. 1 2 Noyes, Katherine (1 August 2013). "Docker: A 'Shipping Container' for Linux Code". Linux.com. Retrieved 2013-08-09.
  14. 1 2 Avram, Abel (2013-03-27). "Docker: Automated and Consistent Software Deployments". InfoQ. Retrieved 2013-08-09.
  15. 1 2 Swan, Chris (2014-03-13). "Docker drops LXC as default execution environment". InfoQ. Retrieved 2015-01-20.
  16. ↑ "8 surprising facts about real Docker adoption". Datadog. June 2016. Retrieved 2016-11-14.
  17. ↑ Hall, Adron (31 July 2013). "OSCON : Conversations, Deployments, Architecture, Docker and the Future?". CloudAve. Retrieved 2013-08-09.
  18. ↑ Reeder, Travis (22 April 2014). "How Docker Helped Us Achieve the (Near) Impossible". Iron.io. Retrieved 2014-07-25.
  19. ↑ "Amazon EC2 - Docker Documentation". docs.docker.com. Retrieved 2014-10-18.
  20. ↑ /. "ansible/library/cloud/docker". GitHub. Retrieved 2014-01-20.
  21. ↑ "CFEngine". CFEngine. Retrieved 2014-06-06.
  22. ↑ "thoward/docker-cookbook". GitHub. Retrieved 2014-01-20.
  23. ↑ "Containers on Google Cloud Platform". Google Inc.
  24. ↑ "Bluemix Launches IBM Containers Beta Based on Docker". IBM. 2014-12-04. Retrieved 2015-04-20.
  25. ↑ "Jelastic Announces Docker Integration to Provide the Most Advanced Orchestrated Application Delivery". PRWeb. Retrieved 2014-12-03.
  26. ↑ "georgebashi/jenkins-docker-plugin". GitHub. Retrieved 2014-01-20.
  27. ↑ "The Docker Virtual Machine Extension for Linux on Azure". Microsoft. 29 June 2015. Retrieved 11 August 2015.
  28. ↑ Stefano Maffulli  June 7th, 2013 (2013-06-07). "OpenStack Community Weekly Newsletter (May 31 – June 7) » The OpenStack Blog". Openstack.org. Retrieved 2014-01-20.
  29. ↑ "OpenSVC Docker". OpenSVC. Retrieved 2014-05-29.
  30. ↑ Gareth Rushgrove. "garethr/docker". Puppet Forge. Retrieved 2014-01-20.
  31. ↑ "saltstack/dockerio". Retrieved 2014-01-20.
  32. ↑ "philspitler/vagrant-docker". GitHub. Retrieved 2014-01-20.
  33. ↑ http://searchservervirtualization.techtarget.com/definition/VMware-vSphere-Integrated-Containers-VIC VMware vSphere Integrated Containers (VIC)
  34. ↑ http://thenewstack.io/vmwares-photon-platform-and-how-it-treats-containers/ VMware’s Photon Platform and How it Treats Containers
  35. ↑ Whelan, Phil (2014-09-03). "Cloud Foundry: Diego Explained By Onsi Fakhouri". ActiveState. Retrieved 2015-04-20. Functionality is being added to enable end-users to push Docker images directly into a Cloud Foundry cluster running Diego.
  36. ↑ Jackson, Joab (2014-04-16). "Red Hat to update Docker container tech for enterprises: Open source vendor plans to incorporate advanced Linux tools such as systemd and SELinux into Docker". Computerworld. Computerworld, Inc. Retrieved 2014-05-29. Red Hat has also started a second community project, called GearD, to integrate Docker into its PaaS (platform-as-a-service) hosting software, OpenShift Origin.
  37. ↑ Verge, Jason (2015-04-28). "PaaS and Docker Containers Work Together in Latest Apprenda Release". Data Center Knowledge. Retrieved 2015-12-06. The 6.0 release integrates Docker’s flexibility and portability with the compliance, governance and security capabilities that enterprises need from PaaS.
  38. ↑ "One home for all your apps". dotcloud.com. Retrieved 2014-05-08.
  39. ↑ "dotcloud/docker". github.com. Retrieved 2015-04-13.
  40. ↑ "Docker - Updated project statistics". Gist. Retrieved 2016-08-22.
  41. ↑ "DotCloud Pivots And Wins Big With Docker, The Cloud Service Now Part Of Red Hat OpenShift". TechCrunch. 2013-09-19. Retrieved 2014-01-20.
  42. ↑ Mary Jo Foley (2014-10-15). "Docker container support coming to Microsoft's next Windows Server release". ZDNet. Retrieved 2014-10-16.
  43. ↑ Scott Guthrie (October 15, 2014). "Docker and Microsoft: Integrating Docker with Windows Server and Microsoft Azure". Microsoft. Retrieved 2015-01-12.
  44. ↑ "IBM and Docker Announce Strategic Partnership to Deliver Enterprise Applications in the Cloud and On Prem". IBM. 2014-12-04. Retrieved 2015-04-20.
  45. ↑ Frederic Lardinois (2015-06-22). "Docker, CoreOS, Google, Microsoft, Amazon And Others Come Together To Develop Common Container Standard". TechCrunch. Retrieved 2015-08-08.
  46. ↑ Shirley Siluk (2015-06-22). "Docker, Tech Giants Team on Open Container Project". cio-today.com. Retrieved 2015-08-08.
  47. ↑ "Announcing Windows 10 Insider Preview Build 14361". Microsoft. 2016-06-08. Retrieved 2016-06-19.
  48. ↑ Cloud; Apple; Microsoft; Google; Oracle; clouds, Docker emits InfraKit to wrangle containers on competing; disrupter, Dell EMC 'backs' Huawei open-source management; cloud, SETI's mega alien hunt shovels more data onto IBM's. "Docker emits InfraKit to wrangle containers on competing clouds". Retrieved 2016-10-07.
  49. ↑ "Docker Debuts Infrakit Open Source Toolkit for Self-Healing Infrastructure". www.serverwatch.com. Retrieved 2016-10-07.

External links

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