How to create docker image file

With the development of cloud computing and the popularization of applications, Docker technology has attracted more and more attention and has become an indispensable part of modern software development and deployment. As the carrier of Docker container operation, Docker image is produced and managed. The importance cannot be underestimated. This article will introduce the concept of Docker images, how to create Docker images, and common Docker image management operations.

1. The concept of Docker image

Docker image is a lightweight, executable independent software package that contains all the files and configurations required to run the program. These files and configurations include: operating system, application code, libraries, environment variables, configuration files, and more. Docker images provide a standard operating environment that can help us quickly deploy, migrate and expand applications.

Docker images adopt a layered storage method. Each image is composed of a series of read-only layers. The top layer is a read-write layer (also called the container layer), which is used to store application data. and modified configuration files. This layered structure makes Docker images very lightweight and can be quickly created, copied and transferred, while also saving storage space.

2. How to make a Docker image

The production of Docker image is based on the Dockerfile file. The Dockerfile file is a text file that contains a series of instructions and parameters. Docker parses these Instructions and parameters automatically build the image. Below we will introduce the basic steps for making a Docker image.

1. Writing a Dockerfile

Before we start making a Docker image, we need to write a Dockerfile. This file contains a series of instructions and parameters to guide Docker. How to build an image. Dockerfile files usually consist of a base image, application code and some configuration files.

The following is a simple Dockerfile example:

FROM ubuntu:18.04

RUN apt-get update && \
    apt-get install -y nginx && \
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*

COPY nginx.conf /etc/nginx/nginx.conf

CMD ["nginx", "-g", "daemon off;"]

The meaning of this Dockerfile is: build a new image based on the Ubuntu 18.04 image, and install the Nginx application server and configuration files. When running this image, Nginx will run as a daemon.

2. Build the Docker image

After writing the Dockerfile file, we can start building the Docker image. Use the following command to build a new image:

docker build -t <image_name>:<tag> .</tag></image_name>

Where, <image_name>:<tag></tag></image_name> is the name and tag of the image, . represents the Dockerfile The path where the file is located. For example, we can use the following command to build an image named mynginx:

docker build -t mynginx:1.0.0 .

This command will look for the Dockerfile file in the current directory and build an image named mynginx, the image labeled 1.0.0.

3. Run the Docker image

After the Docker image is built, we can run the image and test whether the application works correctly. Use the following command to run a new container:

docker run -d -p <host_port>:<container_port> <image_name>:<tag></tag></image_name></container_port></host_port>

Among them, -d means running the container in the background, -p means mapping the container's port to the host's port, <host_port></host_port> represents the host port, <container_port></container_port> represents the port inside the container. For example, we can use the following command to run the mynginx mirror:

docker run -d -p 80:80 mynginx:1.0.0

This command will run a file named mynginx in the background with the label 1.0.0 container, and map port 80 of the container to port 80 of the host.

3. Docker image management

Docker image management is an important part of running Docker containers. The following are common Docker image management operations.

1. View Docker images

Use the following command to view all local Docker images:

docker images

This command will list all local Docker images , including image name, label, size and other information.

2. Delete Docker image

Use the following command to delete a local Docker image:

docker rmi <image_name>:<tag></tag></image_name>

For example, we can use the following command to delete mynginx Image:

docker rmi mynginx:1.0.0

This command will delete the local Docker image named mynginx and labeled 1.0.0.

3. Pull Docker image

Use the following command to pull a Docker image from Docker Hub:

docker pull <image_name>:<tag></tag></image_name>

For example, we can use the following Command to pull the Nginx image from Docker Hub:

docker pull nginx:latest

This command will pull the latest version of Nginx image from Docker Hub.

4. Push Docker Image

Use the following command to push a local Docker image to Docker Hub:

docker push <image_name>:<tag></tag></image_name>

For example, we can use the following command Push the local image named mynginx and labeled 1.0.0 to Docker Hub:

docker push mynginx:1.0.0

This command will push the image to Docker Hub so that It can be shared with other developers or production environments.

4. Summary

This article briefly introduces the concept, production and management of Docker images, hoping to help readers better understand and apply Docker technology. Producing high-quality Docker images is an important part of ensuring the stability and reliability of Docker container operations. It requires the cooperation of developers and operation and maintenance personnel to produce and manage them in detail.

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