![]() ![]() Multiple containers, either of the same image or different images, run on the Docker host.ĭocker images are read-only templates from which Docker containers are launched. The new container can be created using the run command, which runs the container using the image definition. For example, WildFly and Couchbase are downloaded in this case. Each image would represent a different software component. Multiple images can be downloaded from the registry and installed on the host. If not, then it downloads the image from the registry. The Docker Engine checks to see if the image already exists on the host. Docker host downloads the image from the registry The client can pull a prebuilt image from the preconfigured registry using the pull command, create a new image using the build command, or run a container using the run command. The Docker Engine could be on a different host in the network as well. For development purposes, the client and Docker Engine typically are located on the same machine. The Docker client binary is downloaded on a machine and configured to talk to this Docker Engine. These steps are now explained in detail: Docker hostĪ machine, either physical or virtual, is identified to run the Docker Engine. The client is a Docker binary that accepts commands from the user and communicates back and forth with the Docker Engine. It does the heavy lifting of building images, and runs, distributes, and scales Docker containers. Containers can be run, started, scaled, stopped, moved, and deleted.Ī typical developer workflow involves running Docker Engine on a host machine as shown in Figure 1-3. Docker container is a runtime representation of an image. The ability to deploy, manage, and scale these applications. ![]() This is the default registry for all images. Docker images are stored, shared, and managed in a Docker registry.ĭocker Hub is a publicly available registry. ShipĪllows you to share these applications in a secure and collaborative manner. Developers package the application, its dependencies and infrastructure, as read-only templates. Provides tools you can use to create containerized applications. This allows a Docker image to be created once and deployed on a variety of operating systems where Docker virtualization is available.ĭocker simplifies software delivery of distributed applications in three ways: Build Similar to WORA in Java, Docker provides Package Once Deploy Anywhere, or PODA, as shown in Figure 1-2. At the time of writing, there is no native support for Docker on Windows and OS X. It provides a common runtime API, image format, and toolset for building, shipping, and running containers on Linux. ![]() These images are then used to create Docker containers that run on the container virtualization platform, which is provided by Docker.ĭocker simplifies software delivery by making it easy to build, ship, and run distributed applications. Docker simplifies this process by allowing you to create an image that contains your application and infrastructure together, managed as one component. Typically, building, deploying, and running an application requires a script that will download, install, and configure these dependencies. The application, its dependencies, and infrastructure together may be referred to as the application operating system. It may need to tune the configuration files and include multiple other dependencies. It may need binding to specific ports and requires a certain amount of memory. Your Java application typically requires an infrastructure such as a specific version of operating system, an application server, JDK, and a database server. Java provides a common API, runtime, and tooling that works across multiple hosts.
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