Introduction: Learning Objectives
After this section, you will be able to:
- Build a container image using a Dockerfile.
- Create a running container using an image.
- And describe key Docker commands.
This diagram shows the development process of a running container.
How to Create a Container?
The steps to create and run containers are:
- Create a Dockerfile.
- Use the Dockerfile to create a container image.
- And use the container image to create a running container.
- Use a Dockerfile to create a running container.
FROM alpine CMD ["echo", "Hello World!"]
This sample Dockerfile has the commands FROM and CMD.
FROM defines the base image.
And CMD prints the words ”Hello World!” on the terminal.
Docker build command
The Docker build command create a container image usage the Dockerfile.
docker build -t my-app:v1 .
Note: You’ll notice that this Docker command uses the build command, the tag, the repository, the version, and the current directory.
After you run this build command, the output messages include:
Sending build context to Docker daemon “Successfully built <image id>”, which confirms image creation and “Successfully tagged my-app:v1”, which confirms the tag.
Docker Image Verification
To verify the creation of the image, run the “docker images” command.
$ docker images
The output displays the repository (my-app), as well as the tag (v1), image ID, creation date, and the image size.
Docker run Command
Create the container using the run command with the container image name and tag.
$ docker run my-app:v1
The application prints the words “Hello, world!!”
Execute the docker ps -a command, which displays the details of the container created.
$ docker ps -a
Given the appropriate input,
- The build command is used to create container images with tags from a Dockerfile.
- The images command will list all the images, their repositories and tags, and their sizes.
- The run command creates and runs a container from an image.
- The push command stores images in a configured registry and,
- The pull command retrieves images from a configured registry.
In this section, you learned that:
- The build command is used with a Dockerfile to build a container image,
- The run command is used with an image to create a running container,
- And key Dockerfile commands include build, images, run, pull, and push.