How docker runs a program

Docker is a popular container technology that is widely used in software development and deployment. Docker allows developers to package applications and their associated dependencies in a portable container for rapid deployment and operation in any environment. In this article, we will discuss how to run programs using Docker.

1. Install Docker

Before running the program, you need to install Docker. The installation process of Docker is very simple, and detailed installation instructions are provided on the Docker official website (https://www.docker.com/get-started). Depending on your operating system, follow the instructions to download and install Docker.

2. Writing Dockerfile

Dockerfile is an important concept in Docker. It provides a manifest for building a Docker image. A Dockerfile contains a series of instructions that describe how to build a Docker image. Each of these instructions creates a new image layer. A simple Dockerfile is shown below:

FROM python:3.7-slim-buster
WORKDIR /app
COPY requirements.txt /app
RUN pip install --no-cache-dir -r requirements.txt
COPY . /app
CMD ["python", "app.py"]

This Dockerfile will build an image based on Python 3.7. It first sets the current directory to /app and copies requirements.txt and the entire application to /app. It will then install the dependencies listed in requirements.txt and finally run app.py as the container’s default command.

3. Build the Docker image

After completing the Dockerfile, run the following command to build the Docker image:

docker build -t myapp .

Among them, myapp is the name of the image, and . indicates the current directory. This command will build a new image based on the Dockerfile and then save it to the local Docker Registry.

4. Run the Docker container

After building the Docker image, you can run the Docker container through the following command:

docker run -e ENV_VAR=value -p 5000:5000 myapp

Among them, myapp is the name of the Docker image, and the -e option You can set environment variables in the container, and the -p option maps the container's port to the host. In this example, the container's port 5000 will be mapped to the host's port 5000. Finally, run the myapp command to start the container. This command will execute the command specified by CMD in the Dockerfile.

5. Enter the Docker container

Sometimes, you need to enter the running Docker container to execute some commands. You can use the following command to enter the Docker container:

docker exec -it <container_name_or_id> bash

where, b10b500ee54cee6a0872d0dff4e6e1e7 is the name or ID of the Docker container. This command will start a new bash session in the Docker container.

6. End and delete the Docker container

After the operation is completed, you need to end and delete the Docker container to release resources. These operations can be performed through the following command:

docker stop <container_name_or_id>
docker rm <container_name_or_id>

where, b10b500ee54cee6a0872d0dff4e6e1e7 is the name or ID of the Docker container. The docker stop command will end the running of the Docker container, and the docker rm command will delete the Docker container.

Summary

The process of running the program can be easily managed by Docker, allowing for rapid deployment. Using Docker can reduce the workload of operation and maintenance and improve the security and reliability of applications. In the above steps, we learned how to build a Docker image and run a Docker container. These operations can allow developers to focus more on application development.

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