How to create a Docker container from an existing image

To create a Docker container from an existing image, you can use the docker run command. Here are the steps:

1. Pull or Build the Image: First, ensure you have the Docker image available locally. You can either pull an existing image from a registry like Docker Hub using docker pull <image_name>, or build an image from a Dockerfile using docker build -t <image_name> .
2. Create and Start the Container: Once you have the image, run the following command to create and start a new container from that image:

docker run [OPTIONS] <image_name> [COMMAND] [ARG...]

Replace <image_name> with the name of the image you want to use. You can also pass additional options and commands:

• -d or --detach: Run the container in detached mode (in the background)
• -p or --publish: Publish a container’s port to the host (e.g., -p 8080:80 to map host’s 8080 to container’s 80)
• -v or --volume: Bind mount a volume (e.g., -v /host/path:/container/path)
• -e or --env: Set environment variables
• --name: Assign a name to the container
• [COMMAND]: The command to run in the container (if different from the image’s default)

For example, to create and start a new container from the nginx image in detached mode and map port 8080 on the host to 80 in the container, you would run:

docker run -d -p 8080:80 nginx

This will pull the nginx image (if not available locally), create a new container instance from it, and start the container in the background while mapping port 8080 to 80.[1][5]

3. Verify the Container: After running the docker run command, it will output the container ID. You can verify that the container is running using docker ps to list all running containers.[1][4]

You can also create a container without starting it by using docker create instead of docker run. This is useful when you want to create and configure the container before running it later with docker start <container_id>.[2]

Citations:
[1] https://blog.iron.io/how-to-create-a-docker-container/
[2] https://docs.docker.com/reference/cli/docker/container/create/
[3] https://datascientest.com/en/docker-tutorial-how-to-create-your-first-container
[4] https://docs.docker.com/get-started/02_our_app/
[5] https://stackoverflow.com/questions/39076153/how-to-create-container-in-docker