Dockerfile Overriding ENV variable

Question

I have a Dockerfile and I'd like to make the API configurable with a default value.

FROM socialengine/nginx-spa

ENV API_URL localhost:6007

So when I run this image I'd to be able to override the localhost:6007 with something like below:

docker run -e API_URL=production.com:6007 ui

This doesn't work and I can't find a clear explanation of how to do this.

Any advice?

Answer 1

What you have described should work just fine. Given:

$ cat Dockerfile FROM socialengine/nginx-spa ENV API_URL localhost:6007 $ docker build -t ui . [...] 

Consider this:

$ docker run -it --rm ui env | grep API_URL API_URL=localhost:6007 

Compared to:

$ docker run -it --rm -e API_URL='production:6007' ui env | grep API_URL API_URL=production:6007 

Passing a -e VARNAME=varvalue on the docker run command line will override a default set in your Dockerfile.

If you are seeing different behavior, please update your question to show exactly the command you are running and the associated output.