What is Dockerfile ENV? | Bootcamps

The tool of Dockerfile ENV refers to the option that allows you to define environment variables that can be used inside the platform containers.

To set Dockerfile ENV values, the user has the ability to take advantage of starting or booting containers, but also you can provide these variables by default inside the Dockerfile through coding.

So the Dockerfile ENV instruction is responsible for setting the environment variable to a certain value, which is in a specific environment, available for instructions that are implemented later during the compilation stage. This value will be interpreted for other environment variables.

The system sets the Dockerfile tool syntax as ENV =…and can be replaced by the alternative format ENV , where the “=” element is removed. It should be noted that this Alternate syntax does not allow user to set multiple environment variables in a single ENV statement, so it can be confusing.

Dockerfile ENV Features

The Dockerfile ENV option has a series of properties and elements that characterize it, including that, unlike other tools such as Dockerfile ARG values, ENVs cannot be provided directly when creating an image in Dockerbut you can use ARG to set these values ​​by default and work together within the system ( docker arg env ).

After the Docker image has been created, the user has the ability to start containers and provide values ​​for Dockerfile ENV variables through different mechanisms, such as from the command line or the file named docker-compose.yml. These options will be responsible for carrying out the override processes any .env dockerfile value that was pre-established inside the container, even those that are not explicitly set inside the Dockerfile.

In addition to this, the Dockerfile ENV instruction is characterized by allow docker and value environment variable options to set more than one variable at a time. So environment variables set using the ENV option have the ability to persist, that is, remain on the system, even when a Docker container is run from a platform image. These values ​​can be displayed by using the command docker inspect.

Docker also recommends that if an environment variable is only required during the build and is not needed in the final image, the user should set a value for a single command.

What is the next step?

In this article you have been able to learn what the Dockerfile ENV instruction is and what its most important characteristics and functions are within the Docker container platform. Now that you have reached this point, do not hesitate to take the next step to continue with your training process regarding this and many other resources in the IT sector. To do this, we recommend our DevOps & Cloud Computing Full Stack Bootcampwhere in just 6 months you will be able to learn everything you need to stand out in the technological world. Go ahead and sign up for this bootcamp and keep training!