![]() ![]() Docker Compose is a tool for defining and running multi-container Docker applications.Docker registries also allow the creation of notifications based on events. Docker Hub is the default registry where Docker looks for images. Docker clients connect to registries to download ("pull") images for use or upload ("push") images that they have built. Registries: A Docker registry is a repository for Docker images.The result is known as a swarm, a set of cooperating daemons that communicate through the Docker API. A Docker service allows containers to be scaled across multiple Docker daemons.Images are used to store and ship applications. A Docker image is a read-only template used to build containers.A container is managed using the Docker API or CLI. A Docker container is a standardized, encapsulated environment that runs applications.The main classes of Docker objects are images, containers, and services. Objects: Docker objects are various entities used to assemble an application in Docker.The Docker client program, called docker, provides a command-line interface (CLI) that allows users to interact with Docker daemons. The daemon listens for requests sent via the Docker Engine API. Software: The Docker daemon, called dockerd, is a persistent process that manages Docker containers and handles container objects.The Docker software as a service offering consists of three components: The scope of such a license statement is only the Dockerfile and not the container image. The Dockerfile files can be licensed under an open-source license themselves.Docker Desktop distributes some components that are licensed under the GNU General Public License. The Docker Engine is licensed under the Apache License 2.0.ĭocker implements a high-level API to provide lightweight containers that run processes in isolation. Since version 0.9, Docker includes its own component (called libcontainer) to use virtualization facilities provided directly by the Linux kernel, in addition to using abstracted virtualization interfaces via libvirt, LXC and systemd-nspawn. ![]() The Linux kernel's support for namespaces mostly 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. It can also be installed on a single board computer like the Raspberry Pi. 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. ![]() īecause Docker containers are lightweight, a single server or virtual machine can run several containers simultaneously. Docker on macOS uses a Linux virtual machine to run the containers. When running on Linux, Docker uses the resource isolation features of the Linux kernel (such as cgroups and kernel namespaces) and a union-capable file system (such as OverlayFS) to allow containers to run within a single Linux instance, avoiding the overhead of starting and maintaining virtual machines. This enables the application to run in a variety of locations, such as on-premises, in public (see decentralized computing, distributed computing, and cloud computing) or private cloud. ĭocker can package an application and its dependencies in a virtual container that can run on any Linux, Windows, or macOS computer. ![]() Operation Docker can use different interfaces to access virtualization features of the Linux kernel. Because all of the containers share the services of a single operating system kernel, they use fewer resources than virtual machines. ĭocker is a tool that is used to automate the deployment of applications in lightweight containers so that applications can work efficiently in different environments in isolation.Ĭontainers are isolated from one another and bundle their own software, libraries and configuration files they can communicate with each other through well-defined channels. It was first started in 2013 and is developed by Docker, Inc. The software that hosts the containers is called Docker Engine. The service has both free and premium tiers. Docker is a set of platform as a service (PaaS) products that use OS-level virtualization to deliver software in packages called containers. ![]()
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