[SOLVED] How to pass ALL environment variables to container with docker exec

Issue

It's possible to set one or more environment variables in the container while doing docker exec, for example:

docker exec -ti -e VAR=1 -e HOME container_name command

But I would like to pass all the shell's environment variables without explicitly specifying them individually. Essentially the equivalent of sudo -E, although it's a different thing.

According to the documentation, there is no such option. But one hack would be something like:

env > env_vars && docker exec -ti --env-file ./env_vars container_name command

Which works, but I'm looking for a simple one step solution that doesn't involve creating a temporary file. Perhaps a bash trick I don't know or haven't thought of yet. Thanks.

Please note: Passing all environment variables is not recommended and defeats the purpose of container process isolation. This question is for knowledge, not about what should be done. Also, the question is specifically about running a temporary command in an existing container with docker exec, not about docker run.

Solution

With Bash it seems using process substitution work:

docker run --rm -ti --env-file <(env) alpine sh

Note, this creates a temporary fifo file behind the scenes anyway.

Note, this will not work properly with variables containing newlines, they are cutoff on newlines. You should do something along, I tried to make it short:

readarray -d '' -t args < <(env -0 | sed -z 's/^/--env\x00/')
docker run --rm -ti "${args[@]}" alpine sh

Answered By - KamilCuk

Answer Checked By - Timothy Miller (WPSolving Admin)