We use a Dockerfile to build a Docker Image, we can write specific instructions such a install a package, update the system and define the ports that the container will be listen.
In the following example we write a Dockerfile in the /root directory
## Dockerfile that modifies centos:latest FROM centos:latest MAINTAINER User Name <firstname.lastname@example.org> ## Update the server OS RUN yum -y upgrade ## Install Apache Web Server RUN yum -y install httpd ## Install OpenSSH-Server RUN yum -y install openssh-server ## Expose the SSH and Web Ports for attachment EXPOSE 22 80
Now we execute the build command
docker build -t mycustomimg/withservices:v1 /root
Once the image is build we verify that the image is in our list.