54 lines
2.1 KiB
Markdown
54 lines
2.1 KiB
Markdown
---
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categories:
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- DevOps
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tags: [docker, containerization]
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---
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# Docker: general overview
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> Docker is an ecosystem of tools for creating, running and transporting containers.
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The main product of the Docker company is Docker Desktop - a UI for running containers however the actual `docker` software is free and open source.
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Docker standardised the use of containers set up the open-source Open Container Initiative which is a convention agreed upon by the major tech companies. It codifies the following:
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- Docker runtime specification
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- Docker image specification
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- Docker registry specification
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## Main components
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- **Docker Engine**
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- The core component
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- Exposes the Docker API and manages the entire workflow around creating, running and deploying containers
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- **Docker Client**
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- The Docker CLI
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- The primary means of interacting with the Docker Engine
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- Provides commands for managing images, containers and other Docker objects
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- **Docker Compose**
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- A tool for defining and running multi-container applications
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- Define the configuration for all of the containers that make up the application in a single YAML file
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- **Docker Images**
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- See below
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- **Docker Containers**
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- See below
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- **Docker Registry**
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- A centralised location where Docker iamges can be stored and shared
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- DockerHub is the registry provided by Docker
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- Organisations can set up their own private registries
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## Docker images
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An image is a blueprint that contains the instructions to build a container. It's an immutable snapshot of the file system and configuration of an application. Images can be easily shared between developers.
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They are runnable packages that contain everything needed to run an application including the binaries, libraries, resources and other dependencies.
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It does not contain an operating sytem but may include a particular Linux distribution.
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## Docker containers
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A container is a runnign instance of a Docker image. Multiple, identical containers can be launched from the same, single image.
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## Docker architectural overview
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See [Docker architecture](/DevOps/Docker/Docker_architecture.md).
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