Docker is currently a popular containerization technology. The Docker image is the basic unit for Docker to run and the source of creation of Docker containers. A Docker image can be regarded as an independent part of an application, which contains all the components required by the application, including operating system, middleware, code library, etc. This article will introduce how to make Docker images and commonly used Docker image management tools.
Before explaining in depth how to make a Docker image, let me introduce some basic concepts to you.
The Dockerfile file is a text file that describes the Docker image building process. It contains some instructions and parameters for defining the basic settings of the Docker image and executing the build steps.
Docker image adopts a layered storage model. Each layer contains different parts of the image, forming a complete image. When we specify an image as the base image of another image, we only need to merge the layers of the base image with the layers of the new image.
Docker Image Warehouse is a place where Docker images are stored, similar to a Git warehouse, which contains various information about Docker images. Docker supports the use of different image warehouses, such as Docker official warehouse, private warehouse, etc.
There are two main ways to make a Docker image, one is to build the image through the Dockerfile file, and the other is to create the image through container submission.
Dockerfile file is a text file describing the Docker image building process. Docker image can be built through Dockerfile file.
The following is a simple Dockerfile example, used to build a Docker image running Nginx server:
FROM nginx:latest # 基于官方的 Nginx 镜像 COPY ./index.html /usr/share/nginx/html/index.html # 将本地的 index.html 文件拷贝到镜像内 EXPOSE 80 # 开放 80 端口 CMD ["nginx", "-g", "daemon off;"] # 启动 Nginx 服务器
Among them, the FROM instruction specifies the base image, and the COPY instruction changes the local index.html The file is copied to the Docker image. The EXPOSE command defines the port number opened by the image, and the CMD command defines the default command when the container is started.
You can build the above Docker image locally by executing the following command:
docker build -t my-nginx .
Among them, the -t parameter specifies the image name and label, and the . parameter represents the directory path where the Dockerfile file is located, or Specify the Dockerfile file path.
In addition to building Docker images through Dockerfile files, Docker also provides a container-based way to create images. This method requires running the application through a Docker container first, and then submitting the container to a new Docker image.
The following is a simple container-based Docker image creation example:
First, we need to run an nginx container:
docker run --name my-nginx nginx:latest
Then, submit the nginx container through the following command For the new image:
docker commit my-nginx my-nginx-new
where, my-nginx is the name of the currently running container, and my-nginx-new is the name of the new image. In this way, we can quickly submit a container as a new image.
Docker image management is an important topic, and Docker image management tool is a tool that helps us manage Docker images. The following are some common Docker image management tool.
The docker command is the command line tool of Docker. It provides many commonly used Docker image management commands, such as docker images, docker pull, docker push, etc.
Docker Hub is the official Docker image warehouse, which contains a large number of Docker images. Users can search, pull and upload Docker images through Docker Hub.
Docker Compose is the Docker application orchestration tool officially provided by Docker. It can define the relationship and running configuration between various services of the Docker application through YAML files. Docker Compose can also help users manage Docker images, including pulling, building and publishing, etc.
This article introduces the basic concepts, production methods and common Docker image management tools of Docker images. For developers and operators who use Docker technology, it is very necessary to have an in-depth understanding of Docker images.
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