Multi tool use

dockerd set default environment variable for all containers

I have a docker daemon running behind an HTTP proxy.

My Dockerfile's look like this:

Dockerfile

FROM alpine:latest

RUN apk add --no-cache make gcc


Normally I configure the proxy by adding the http_proxy environment variable to the Dockerfile:

http_proxy

Dockerfile

FROM alpine:latest

ENV http_proxy http://myproxy.mydomain.com:8080/

RUN apk add --no-cache make gcc


And that works fine.

But I don't want to touch the Dockerfile because it is also used in other environments where the proxy isn't available. I don't want to have ENV http_proxy ... in the Dockerfile at all.

Dockerfile

ENV http_proxy ...

Dockerfile

So my question is: how to add an environment variable to all containers without touching the Dockerfiles?

Dockerfile

2 Answers
2

Try like this

Dockerfile

FROM alpine:latest

ARG HTTP_PROXY_ARGUMENT

ENV http_proxy ${HTTP_PROXY_ARGUMENT}

RUN apk add --no-cache make gcc


Build like below

docker build -t --build-arg HTTP_PROXY_ARGUMENT=http://myproxy.mydomain.com:8080/ imagename .


With adding a environment variable on run ?

https://docs.docker.com/engine/reference/run/#env-environment-variables

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