Your first Dockerfile should be your blueprint or recipe card for your application. Herein you list the ingredients (base image), the preparation steps (copying code, installing dependencies), and the final presentation (how your app starts). Docker will then take this recipe and create a portable, self-contained meal that will taste exactly the same on any server! Configuration nightmares on the servers are now history; your application is ready to be shipped!
First at play with creating your own Docker image? That’s great! But keep it on hold for a bit while you’re all about installing, starting, and understanding the basic stuff of Docker. It’s just like learning the traffic rules before sitting behind the wheel.
What is a Docker Image?
A Docker image is analogous to a notorious shipping container for the application. It catches everything – code, runtime, system tools, system libraries, settings -in one go, and ships the composed application running smoothly from the development environment to production, regardless of whatever environment it considers to be. Deployment is eventually the more predictable, the more reliable, and just less chaotic.
What Is a Dockerfile?
Think of a Dockerfile as a recipe. This recipe lists the exact ingredients (commands) and steps to bake your custom Docker image, written in Docker’s own special language. It is the container’s development manifesto that ensures consistency and reproduce-ability every single time.
Crafting a Dockerfile early in application development is akin to setting a foundation for a skyscraper. Docker follows each line and instruction within the Dockerfile to build your application’s image, also called “launchpad” on which it traverses its journey.
In short, the Dockerfile serves as the source code for your Docker image.
Building a Docker Image Using a Dockerfile
Docker image-building? It’s really not that complicated! You start by making a plan for your image through a Dockerfile and filling it with clear instructions. Then, all that remains is to type thedocker buildcommand-and your image goes on to be baked in that virtual oven. With the best part? The image is completely self-contained and portable so that containers can be launched anywhere on any Docker-furnished machine.
Create a New Dockerfile
Let’s create a Dockerfile in your project folder using an editor, like Vim, Nano, etc.
“`
nano
Dockerfile “`
The idea behind thinking that Dockerfile is set in stone is totally wrong! Though Docker will try to look for a file named “Dockerfile” to build your image, you are not chained to it. Channel your rebellious spirit and name the build file whatever you want! Remember, though, you will have to specify this to Docker using the-fflag in thedocker buildcommand.
Add Instructions to the Dockerfile
Let’s specify the following code in the Dockerfile to define the environment for your Python app:
“` FROM ubuntu:latest WORKDIR
/
usr
/
src
/
app COPY . . RUN
apt-get update
&&
apt-get install
-y
\ python3 \ python3-pip CMD
[
“python3”
,
“mteScript.py”
]
“`
Imagine a playground: your codes getting effortlessly transported from your local machine to a perfectly configured containerized environment. Using Ubuntu as our launchboy, we conduct this magic. First, your project files are teleported in the container. Then Python and Pip have to be installed in it for work. Lastly, the stage is set for your triumph:mteScript.pysits ready to be executed as the curtain rises.
Prepare a Sample Python Script
Now, create a Python file namedmteScript.pyin the same directory as your Dockerfile:
“`
def
message
(
)
:
(
“Hi Geeks! Welcome to maketecheasier.com”
)
if
name
==
“main“
: message
(
)
“`
“And with that, the configuration will issue the script for execution during container startup. Consider it an ‘all systems go’ check, verifying that the image is intact before the jobs turn real.”
Build the Docker Image
That is when you want to forge your Docker image: thedocker runcommand comes in handy! An alchemist’s stone that transmutes the instructions written on a Dockerfile into a ready-to-run image, namedpython-docker-demo.
“`
sudo
docker
build
-t
python-docker-demo . “`
“`
sudo
docker
build
-f
ExampleDockerfile
-t
python-docker-demo . “`
Verify the Docker Image
Once the Docker image is built, you can check if it was created successfully by running this command:
“`
sudo
docker
images “`
This will list all available images on your system, including the one you just built:
Run the Docker Image for Testing
To test your Docker image locally, you can start a container using this command:
“`
sudo
docker
run python-docker-demo “`
Let loose thepython-docker-democontainer! Unpack the look with all its basic setup through console and see for yourself the magic with it.
Final Thoughts
Unloading deployment chains from your applications and granting them real portability should have been first steps after building your very first Docker image with a Dockerfile. Fun thought would be to fine-tune the likeness of environment for your code, ensuring that it will work perfectly well in any situation. It is more than just containers; it is grasping control.
Ready to take your Docker skills to a new level? Get into the art of container optimization, or discover the untold scam: running full-blown GUI apps in the Docker universe.
Thanks for reading How to Create Your First Docker Image with a Dockerfile
