Docker - Images

Docker Images are read-only templates comprised of multiple layers which act as a blueprint of the container environment.

Docker Images are built by specifying instructions inside a special file called Dockerfile.

Dockerfile allows us to define instructions to create a customized container environment.

We can execute the Docker build command on a Dockerfile to create a Docker Image.

This Docker image can then be used to create one or more instances of Docker containers associated with that image.

Running Containers from Docker Image

Steps to create a Docker Image and run a Container

Step 1:

• Create a Dockerfile.

Step 2:

• Run the following command in the terminal and it will create a docker image of the application and download all the necessary dependencies needed for the application to run successfully.
• docker build -t <tag to give to your image>
• This will start building the image.

Step 3:

• We have successfully created a Dockerfile and a respective Docker image for the same.

Step 4:

• Run the following command in the terminal and it will create a running container with all the needed dependencies and start the application.
• docker run -p 9000:80 <tag-name>
• The 9000 is the port we want to access our application on.
• 80 is the port the container is exposing for the host to access.

Useful Docker Image commands:

docker images See the list of Docker images on the system

docker build -t <tag name> . Build the container image

docker run -dp 3000:3000 <tag name> Start the app container using the image

docker rmi <Image ID> Removing Docker Images

docker images -q Return the Image ID’s only

docker inspect <name> Used to see the details fo an image or container