How to assign a port mapping to an existing Docker container?

Better Stack Team
Updated on November 9, 2023

To assign a port mapping to an existing Docker container, you can follow these steps:

  1. Identify the Container: Find the container ID or name of the Docker container you want to modify. You can use the docker ps command to list all running containers:

    docker ps
  2. Stop the Container (if it's running): If the container is running, stop it using the following command. Replace CONTAINER_ID with the actual ID or name of your container:

    docker stop CONTAINER_ID
  3. Remove the Existing Container (if necessary): If you prefer to keep the existing container's data, you can skip this step. However, if you want to start a new container based on the same image but with a different port mapping, you might need to remove the existing container. Be careful as removing a container deletes any changes made inside the container:

    docker rm CONTAINER_ID
  4. Create a New Container with the Desired Port Mapping: You can create a new container based on the existing container's image and define the port mapping at this stage. Use the p flag to map the ports:

  • NEW_HOST_PORT: This is the port on the host machine where you want to map the container's port.
  • EXISTING_CONTAINER_PORT: This is the port inside the container that you want to expose.
  • NEW_CONTAINER_NAME: This is the name you want to assign to the new container.
  • IMAGE_NAME: This is the image of the existing container.
  1. Start the New Container: Once you've created the new container with the modified port mapping, start it:

    docker start NEW_CONTAINER_NAME

Remember to replace the placeholder values (like NEW_HOST_PORT, EXISTING_CONTAINER_PORT, NEW_CONTAINER_NAME, and IMAGE_NAME) with your actual port numbers, container name, and image name.

By following these steps, you can re-create a container based on an existing image with a different port mapping. This allows you to assign a new port to an existing Docker container without directly modifying the port mappings of a running container.

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