For example, to pull the Ubuntu 20.04 Docker image from the Docker Hub.

docker pull ubuntu:20.04

Create a new container from the Ubuntu 20.04 image.

docker run -t -i ubuntu:20.04 /bin/bash

This will create a new container and attach to the bash shell as shown below:

root@013aecdd6919:/#

Install the Nginx package inside the container:

root@013aecdd6919:/# apt-get update -y
root@013aecdd6919:/# apt-get install nginx -y

root@013aecdd6919:/# exit

Locate your new container ID:

docker ps -a

returns:

CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                       PORTS               NAMES
013aecdd6919        ubuntu:20.04        "/bin/bash"         3 minutes ago       Exited (0) 33 seconds ago                        happy_camper

Save the updated container with a new image named nginx-instance:

docker commit "013aecdd6919" nginx-instance

• Where: 013aecdd6919 is the ID of the container.

Verify the newly created image “nginx-instance”:

docker images

returns:

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
nginx-instance      latest              12cefc9b5362        57 seconds ago      158MB
ubuntu              20.04               d70eaf7277ea        12 days ago         72.9MB