Creación de imágenes con Dockerfile

How to build a Docker image with a Dockerfile?

Creating a Docker image may seem challenging, but once you master the process, it makes it easier to distribute and deploy applications. The key is the Dockerfile, an essential file that defines the steps required to build a Docker image. From it, you can create an image that you can easily share. Here's how to do it.

What commands are useful for verifying the location of the Dockerfile?

Before building an image, it is essential to make sure that you are in the correct path in your terminal, where the Dockerfile is located. This can be verified using the ls command in Linux. This command will list the files in the current directory, allowing you to confirm the presence of the required Dockerfile.

How to actually build the Docker image?

To start building the image, use the docker build . command in your terminal. The dot (.) indicates that the Dockerfile is in the current location. When you run the command, Docker will read the instructions from the Dockerfile and start building the image, displaying the sequence of steps executed. You will see something like this:

docker build .

Docker will display the steps performed. For example, "1/2" might indicate that you are downloading a base image such as Nginx, and "2/2" will indicate that you are copying files to the image.

What to do with the unnamed image?

After creating your first image, when using docker images, you might notice that the image appears unnamed and untagged. Although this is the fastest way to create an image, it is not recommended as it results in missing information. If it happens, consider deleting it with the command:

docker rmi -f <image-ID> .

This will delete your image permanently. Use -f (force) in case the image has dependencies that might hinder its removal.

How to properly tag your image?

Labeling an image is basic to identify it easily. When building the image, use -t followed by the name and tag:

docker build -t web-site:latest .

This gives it a name and a label ("latest" indicates the latest version). This way, you will be able to handle different versions of your images with clarity.

What does it mean to have a tagged image?

Once properly labeled, when listing images with docker images, your new image will appear with the specified name and label, e.g. "sitio-web:latest". This makes it easy to manage multiple versions of an application or service.

What's next after creating a Docker image?

With the image creation complete, you can now proceed to deploy to different environments starting with your local environment. This involves running containers based on the image you just built. Having properly labeled images simplifies your organization and the recycling of previous versions.

Dive into the world of Docker and keep expanding your skills. With each step you take, you will be better prepared to orchestrate containerized applications, a valuable skill in modern software development. Keep learning and exploiting the full potential of Docker!