Set Multiline Environment Variable with Dockerfile

Question

I want to set a multiline environment variable in my Dockerfile.

Works through command line

If I pass in the environment variable through docker run everything works.

CONFIG="port: 4466
databases:
  prod:
    connector: mysql
    active: true
    host: 33.333.333.333
    port: 3306
    user: root
    password: pass"
docker run --env CONFIG="$CONFIG" ubuntu:latest env | grep 'CONFIG'

Output (its only a single line because its interpreted as multiline variable)

CONFIG=port: 4466

Doesnt Work through dockerfile

Dockerfile

FROM ubuntu:latest
ENV CONFIG 'port: 4466\ndatabases:\n  prod:\n    connector: mysql\n    active: true\n    host: host\n    port: 3306\n    user: root\n    password: pass'

Build and run the docker image

docker build -t multilinetest .
docker run multilinetest env | grep 'CONFIG'

Output

CONFIG=port: 4466\ndatabases:\n  prod:\n    connector: mysql\n    active: true\n    host: host\n    port: 3306\n    user: root\n    password: pass

Expected

Both scenarios should store the same environment variable (I'm passing this environment variable into a 3rd party image that requires a multiline string)

Dan Rasmuson · Accepted Answer · 2018-08-03 00:37:01Z

28

I was able to get this working by passing the multiline environment variable as a build arg to docker build.

Dockerfile

FROM ubuntu:latest
ARG CONFIG
ENV CONFIG $CONFIG

Build Command

CONFIG="port: 4466
databases:
  prod:
    connector: mysql
    active: true
    host: 33.333.333.333
    port: 3306
    user: root
    password: pass"
docker build --build-arg CONFIG="$CONFIG" ubuntu:latest env | grep 'CONFIG'

edited Aug 3, 2018 at 0:37

answered May 11, 2018 at 20:42

Dan Rasmuson

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Édouard Lopez · Accepted Answer · 2018-11-26 00:32:27Z

11

Escaping newline characters work fine.

Dockerfile

ENV BUILD_DEPENDENCIES apt-utils \
  curl \
  libc-dev \
  gcc \
  gnupg2

Output

Step 8/48 : ENV BUILD_DEPENDENCIES apt-utils   curl   libc-dev   gcc   gnupg2
 ---> Running in 65b0ad105af4

answered Nov 26, 2018 at 0:32

Édouard Lopez

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1 Comment

Gogowitsch Over a year ago

This is not actually the solution because this turns newlines into nothing,

Simon Smith · Accepted Answer · 2024-05-10 19:32:16Z

2

You can do it like this:

ENV CONFIG="port: 4466\n"\
"databases:\n"\
"  prod:\n"\
"    connector: mysql\n"\
"    active: true\n"\
"    host: 33.333.333.333\n"\
"    port: 3306\n"\
"    user: root\n"\
"    password: pass\n"

answered May 10, 2024 at 19:32

Simon Smith

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Comments

mot · Accepted Answer · 2025-04-17 02:10:00Z

0

Unfortunately, Docker does not support multiline by default. You can use dotenvx if you need multiline support with Docker. Just put dotenvx run -- out in front of your docker command.

$ docker run -- docker ...

answered Apr 17 at 2:10

mot

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Set Multiline Environment Variable with Dockerfile

Works through command line

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Works through command line

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Dockerfile

Output

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