Can Docker compose read environment variable?
When you run docker-compose up with this configuration, Compose looks for the POSTGRES_VERSION environment variable in the shell and substitutes its value in. For this example, Compose resolves the image to postgres:9.3 before running the configuration. Both $VARIABLE and ${VARIABLE} syntax are supported.
Does Docker compose inherit environment variables?
If you define an environment variable in the shell or via the command line when running docker-compose , those variables will take precedence over the . env file.
How do you set an environment variable in Python?
To permanently modify the default environment variables, click Start and search for ‘edit environment variables’, or open System properties, Advanced system settings and click the Environment Variables button. In this dialog, you can add or modify User and System variables.
How to substitute an environment variable in Docker?
If you have multiple environment variables, you can substitute them by adding them to a default environment variable file named .env or by providing a path to your environment variables file using the –env-file command line option.
When to change values in Docker-compose.env file?
If you are using docker-compose, the values from .env are used to replace $ {DOLLAR_NOTATION} placeholders in your docker-compose.yml file. But what if you want to change one of the values in the .env file dynamically? You could use something like sed or awk to change the file in-place, but there is a better way.
How to override a value in a.env file?
The “FROM_DOT_ENV” value taken from the .env file made it into the container. As one would expect. Now, let’s try overriding the value defined in the .env file by setting an environment variable in the host’s shell: The container’s NAME variable is set to “ENV”, which is the value of the environment variable.
How to use environment variables in a compose file?
It’s possible to use environment variables in your shell to populate values inside a Compose file: If you have multiple environment variables, you can substitute them by adding them to a default environment variable file named .env or by providing a path to your environment variables file using the –env-file command line option.