Env variable in Dockerfile

Question

I'm trying to dockerize a basic nodejs app. My dockerfile is the follow

FROM node:10

WORKDIR /usr/src/app

COPY package*.json ./

RUN npm install

COPY . .

EXPOSE 80
CMD [ "node", "index.js" ]

After i build the image I'm trying to running it with

docker run -p 3000:3000 imagename -e connectionString=myConnString

But I received always the same error

[eval]:1
connectionString=myConnString

ReferenceError: myConnString is not defined

How can I solve?

Answer 1

The docker run syntax is docker run [OPTIONS] IMAGE[:TAG|@DIGEST] [COMMAND] [ARG...], anything passed after the IMAGE[:TAG|@DIGEST] is passed as [COMMAND] [ARG...].

The environment variable setting should be passed in the run [OPTIONS] i.e.: docker run -p 3000:3000 -e connectionString=myConnString imagename