How to download docker image

Docker is currently the most popular container technology, providing convenient container deployment and management tools. In the process of using Docker, downloading the image is a very important step. This article will introduce how Docker downloads images and the basic concepts of Docker images.

1. What is a Docker image

In Docker, the image is a container image based on the file system, which can be regarded as the basic template for starting a Docker container. The image contains the operating system, applications, libraries, and other dependencies. Docker images are composed of multiple layers of containers, each representing a portion of a change or increment. This hierarchical structure makes Docker images lightweight, easy to copy and distribute, and ensures system stability and consistency.

2. Sources of Docker images

Docker images can be obtained from a variety of sources, including public warehouses, private warehouses and local builds.

1. Public warehouse

Docker Hub is the official public warehouse of Docker, which contains a huge image library and is the main platform for users to obtain and share images. Users can search, upload and download images through the Docker Hub web interface. Docker Hub's image library supports Docker official images and community-contributed images, allowing users to easily find the images they need.

2. Private warehouse

Private warehouse is a warehouse derived from a public warehouse, which provides private storage and distribution functions of Docker images. Users can use private warehouses to build their own Docker image services, so that they can quickly deploy Docker containers in their own private cloud or data center.

3. Local build

Users can build their own Docker images through Dockerfile files. Dockerfile is a text file that contains the building commands and parameters of the Docker container and can be used to describe the image building process. Users can use Dockerfile to build their own images and upload them to private or public repositories.

3. How to download Docker images

There are two main ways for Docker to download images: through the command line and the Docker Hub website. To download a Docker image from the command line, you need to use the docker pull command, which will obtain the specified image from the warehouse and save it to the local computer. To download a Docker image from the Docker Hub website, you need to log in to the Docker Hub website, search and select the Docker image you want to download, and then click the "Download" button to download.

1. Download through the command line

Downloading the Docker image through the command line is very simple, just use the docker pull command. The following is an example of downloading an Ubuntu image:

docker pull ubuntu

After executing this command, Docker will automatically download the Ubuntu image from the Docker Hub image library and save it to the local computer.

If you need to download a specific version of the image, you can use a colon (:) to specify the image label. For example, the following command will download the Ubuntu 18.04 version image:

docker pull ubuntu:18.04

2. Download through the Docker Hub website

Downloading the Docker image through the Docker Hub website is also very simple. Users can search for the required image on the Docker Hub website, and then click the "Download" button to download the image. The downloaded Docker image will be saved on the local computer.

4. Use of Docker image

After downloading the Docker image, you can use the image to create a Docker container. Users can use the docker run command to create a Docker container and specify which Docker image to use. For example, the following command will create a Docker container using the Ubuntu image:

docker run -it ubuntu /bin/bash

After running the above command, Docker will create a Docker container based on the Ubuntu image on the local computer and open a terminal for interaction. Users can operate and manage Docker containers in the terminal.

Summary

Docker image is the basic template of Docker container and an important part of Docker system development and application orchestration. Users can obtain Docker images through public repositories, private repositories, and local builds. To download a Docker image from the command line, you need to use the docker pull command, and to download it from the Docker Hub website, you need to log in to the Docker Hub website. After downloading the Docker image, users can use the docker run command to create a Docker container, and operate and manage the Docker image within the container.

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