Troubleshooting Docker and Kubernetes Containers/

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Ports Availability

Ports Availability

Learn about port mapping and how to ensure their availability.

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Port mapping can be defined as exposing the services inside a container to the host system or external network. It allows traffic to be routed from a specific port on the host to a port within the container. This helps enable communication between the host system and the containerized application. Docker containers operate in an isolated network environment, and the ports aren’t accessible from the host or external network. Port mapping fixes this issue, making containers accessible.

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Various ways of port mapping

In Docker, there are various ways to perform port mapping. Here are some of those methods:

  • Using the docker run command: The docker run command automatically maps a container to a port whether it’s specified or not. It’s written this way:

docker run -d <image_name>

There are occasions when we want to specify the mapping to a particular port. We’ll then write it this way:

docker run -p 8080:80 <image_name>

  • Specifying port mapping in a Docker compose file: In a docker-compose.yml file, we can define port mappings for services using the ports directive. We illustrate that below.

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services:
  web:
    image: nginx
    ports:
      - 8080:80

  • Exposing ports in Dockerfile: In the case where ports are exposed in Dockerfile, there’ll still be a need to use the same port when running the docker run command. If we don’t use the port specified on the Dockerfile when using the docker run command, the port mapping will still work, as long as the port specified in the docker run command ...