Docker is a set of products that usesoperating-system-level virtualization to deliver software in packages calledcontainers. Docker automates the deployment ofapplications within lightweight containers, enabling them to run consistently across different computing environments.
The core software that runs and manages these containers is calledDocker Engine. Docker was first released in 2013 and continues to be developed byDocker, Inc. The platform includes both free and paid tiers.
dotCloud Inc. was founded by Kamel Founadi, Hykes, and Sebastien Pahl[6] during theY Combinator Summer 2010 startup incubator group and launched in 2011, and renamed to Docker Inc in 2013.[7]
Docker debuted to the public inSanta Clara atPyCon in 2013.[8] It was released asopen-source in March 2013.[9] At the time, it usedLXC as its default execution environment. One year later, with the release of version 0.9, Docker replaced LXC with its own component,libcontainer, which was written in theGo programming language.[10][11]
In 2017, Docker created theMoby project [wd] for open research and development.[12]
October 15, 2014:Microsoft announced the integration of the Docker engine intoWindows Server, as well as native support for the Docker client role in Windows.[14][15]
November 10, 2014: Docker announced a partnership withStratoscale.[17]
December 4, 2014:IBM announced a strategic partnership with Docker that enables Docker to integrate more closely with the IBM Cloud.[18]
June 22, 2015: Docker and several other companies announced that they were working on a new vendor and operating-system-independent standard for software containers.[19][20]
December 2015:Oracle Cloud added Docker container support after acquiringStackEngine, a Docker container startup.[21]
April 2016: Windocks, anindependent software vendor released a port of Docker's open source project to Windows, supporting Windows Server 2012 R2 and Server 2016, with all editions of SQL Server 2008 onward.[22]
June 8, 2016: Microsoft announced that Docker could now be used natively onWindows 10.[24]
January 2017: An analysis ofLinkedIn profile mentions showed Docker presence grew by 160% in 2016.[25]
May 6, 2019: Microsoft announced the second version ofWindows Subsystem for Linux (WSL). Docker, Inc. announced that it had started working on a version of Docker for Windows to run on WSL 2.[26] In particular, this meant Docker could run on Windows 10 Home (previously it was limited to Windows Pro and Enterprise since it usedHyper-V).
August 2020: Microsoft announced a backport of WSL2 to Windows 10 versions 1903 and 1909 (previously WSL2 was available only on version 2004)[27] and Docker developers announced availability of Docker for these platforms.[28]
August 2021: Docker Desktop for Windows and MacOS was no longer available free of charge for enterprise users. Docker ended free Docker Desktop use for larger business customers and replaced its Free Plan with a Personal Plan. Docker Engine on Linux distributions remained unaffected.[29]
December 2023: Docker acquired AtomicJar to expand its testing capabilities.[30]
Docker can use different interfaces to access virtualization features of the Linux kernel.[31]
Containers are isolated from one another and bundle their own software,libraries and configuration files; they can communicate with each other through well-defined channels.[32] Because all of the containers share the services of a singleoperating system kernel, they use fewer resources thanvirtual machines.[33]
Because Docker containers arelightweight, a single server or virtual machine can run several containers simultaneously.[37] A 2018 analysis found that a typical Docker use case involves running eight containers per host, and that a quarter of analyzed organizations run 18 or more per host.[38] It can also be installed on a single board computer like theRaspberry Pi.[39]
The Linux kernel's support for namespaces mostly[40] 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 for memory and CPU.[41] Since version 0.9, Docker includes its own component (calledlibcontainer) to use virtualization facilities provided directly by the Linux kernel, in addition to using abstracted virtualization interfaces vialibvirt,LXC andsystemd-nspawn.[10][31][34][42]
Docker implements a high-levelAPI to provide lightweight containers that run processes in isolation.[9]
The Docker software as a service offering consists of three components:
Software
The Dockerdaemon, calleddockerd, is a persistent process that manages Docker containers and handles container objects. The daemon listens for requests that are sent via the Docker Engine API.[43][44] The Docker client program, calleddocker, provides acommand-line interface (CLI) that allows users to interact with Docker daemons.[43][45]
Objects
Docker objects are various entities used to assemble an application in Docker. The main classes of Docker objects are images, containers, and services.[43]
A Dockercontainer is a standardized, encapsulated environment that runs applications.[46] A container is managed using the Docker API orCLI.[43]
A Dockerimage is a read-only template used to build containers. Images are used to store and ship applications.[43]
A Dockerservice allows containers to be scaled across multiple Docker daemons. The result is known as aswarm, a set of cooperating daemons that communicate through the Docker API.[43]
Registries
A Docker registry is a repository for Docker images. Docker clients connect to registries to download ("pull") images for use or upload ("push") images that they have built. Registries can be public or private. The main public registry is Docker Hub. Docker Hub is the default registry where Docker looks for images.[43][47] Docker registries also allow the creation of notifications based on events.[48]
A Dockerfile is a text file that commonly specifies several aspects of a Docker container: theLinux distribution, installation commands for the programming language runtime environment and application source code.
ARGCODE_VERSION=latestFROMubuntu:${CODE_VERSION}COPY./examplefile.txt/examplefile.txtENVMY_ENV_VARIABLE="example_value"RUNapt-getupdate# Mount a directory from the Docker volume# Note: This is usually specified in the 'docker run' command.VOLUME["/myvolume"]# Expose a port (22 for SSH)EXPOSE22
Docker Compose is a tool for defining and running multi-container Docker applications.[50] It usesYAML files to configure the application's services and performs the creation and start-up process of all the containers with a single command. Thedocker compose CLI utility allows users to run commands on multiple containers at once; for example, building images,scaling containers, running containers that were stopped, and more.[51] Commands related to image manipulation, or user-interactive options, are not relevant in Docker Compose because they address one container.[52] Thedocker-compose.yml file is used to define an application's services and includes various configuration options. For example, thebuild option defines configuration options such as the Dockerfile path, thecommand option allows one to override default Docker commands, and more.[53] The first public beta version of Docker Compose (version 0.0.1) was released on December 21, 2013.[54] The first production-ready version (1.0) was made available on October 16, 2014.[55]
Docker Swarm provides nativeclustering functionality for Docker containers, which turns a group of Docker engines into a single virtual Docker engine.[56] In Docker 1.12 and higher, Swarm mode is integrated with Docker Engine.[57] Thedocker swarm CLI[58] utility allows users to run Swarm containers, create discovery tokens, list nodes in the cluster, and more.[59] Thedocker node CLI utility allows users to run various commands to manage nodes in a swarm, for example, listing the nodes in a swarm, updating nodes, and removing nodes from the swarm.[60] Docker manages swarms using theRaftconsensus algorithm. According to Raft, for an update to be performed, the majority of Swarm nodes need to agree on the update.[61][62] In addition to thedocker swarm CLI,docker stack is a tool designed to manage Swarm services with greater flexibility. It can use a configuration file very similar to adocker-compose.yml, with a few nuances. Usingdocker stack instead ofdocker compose offers several advantages, such as the ability to manage a Swarm cluster across multiple machines or the capability to work withdocker secret combined withdocker context, a feature that allows executing Docker commands on a remote host, enabling remote container management.
Docker Volume facilitates the independent persistence of data, allowing data to remain even after the container is deleted or re-created.[63]
The Docker Engine is licensed under theApache License 2.0. Docker Desktop distributes some components that are licensed under theGNU General Public License. Docker Desktop is not free for large enterprises.[64]
The Dockerfile files can be licensed under an open-source license themselves. The scope of such a license statement is only the Dockerfile and not the container image.[citation needed]
^K., Chris (14 January 2019)."Lightweight Windows containers: Using Docker process isolation in Windows 10".Poweruser. Retrieved2 August 2019.more "lightweight" real containers (via so called process-isolation), where the containerized processes are running directly on the host system — all processes on the host and in the containers are sharing the same Windows kernel. This is similar to how containers on Linux work.
^Gupta, Devender (October 13, 2022)."How to Install Docker on Raspberry Pi".Gizmoxo. Archived from the original on February 14, 2025. RetrievedOctober 15, 2022.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
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