docker run -d

Docker run command is used to create a docker container out of docker images. This tutorial is to tell ways to create docker container in detached mode.

So, the first question that came in the mind is what is detached mode. Detached mode means that the when the root process of the host machine on which docker engine is installed exits, the docker container started in detached mode also exits.

How to start docker container in detached mode?

docker run -d=true 

docker run -d

You can start the docker container in detached mode using -d=true (or simply -d) options with docker run interface. 

By default, the docker container starts in foreground mode.

Points to remember when docker container is started in detached mode:

(a) Docker container will not automatically be removed when you stop the container.

(b) Don't start container in detached mode using unix service command. The problem it will face here is that unix service process returns (and exits), so the container will also stop in detached mode due to this.

Docker Container Interview Questions

Docker is a new technology for virtualization. Here are some interview questions and answers on docker container.

How to create docker container?

We can create docker container by running this command

docker run -t -i <image name> <command name>

This will create and start the container

How do you create docker image?

Docker image are created using Docker file. Docker build is command to create docker image out of docker file

So you have the docker image, what is the next step?

With docker image, we can spawn as many containers as needed. All containers can be same instance or it can also be different instance, what I mean that if we are using the same command for creating multiple containers, all container will behave as same. However, if you choose different command to create container out of same image, it will provide different functionality altogether.

How to know the container status?

Just fire docker ps -a to list out all running container with stauts (running or stopped) on a host

How to stop and restart the container?

To stop container, we can use docker stop <container id>

To start a stopped container, docker start <container id> is the command

To restart a running container, docker restart <container id>

Docker Interview Questions and Answers

What is Docker

Docker is a platform to run each application isolated and securely. Internally it achieves it by using kernel containerization feature.

What is the advantage of Docker over hypervisors?

Docker is light weight and more efficient in terms of resource uses because it uses the host underlying kernel rather than creating its own hypervisor. 

What is Docker Image

Docker Image is the source of the docker container. In other words, docker images are used to create containers. It is possible create multiple isolated containers from a single image.

What is Docker Container

Docker Container is the instantiation of docker image. In other words, it is the run time instance of images. Images are set of files whereas containers is the one who run the image inside isolated.

Difference between Docker Image and container?

Docker container is the runtime instance of docker image.

Docker Image doesnot have a state and its state never changes as it is just set of files whereas docker container has its execution state.

To be continued...