How to read system environment variables inside docker container

Question

I am very new to docker. I have a requirement where docker container should read the system environment variable like AWS_INSTANCE_ID which is an instance-id in aws. Normally on bootup, I used to add these environment variables using a shell script as follows

    EC2_INSTANCE_ID="`wget -q -O - http://169.254.169.254/latest/meta-data/instance-id || die \"wget instance-id has failed: $?\"`"
test -n "$EC2_INSTANCE_ID" || die 'cannot obtain instance-id'
export EC2_INSTANCE_ID=$EC2_INSTANCE_ID
EC2_AVAIL_ZONE="`wget -q -O - http://169.254.169.254/latest/meta-data/placement/availability-zone || die \"wget availability-zone has failed: $?\"`"
test -n "$EC2_AVAIL_ZONE" || die 'cannot obtain availability-zone'
export EC2_AVAIL_ZONE=$EC2_AVAIL_ZONE
EC2_REGION="`echo \"$EC2_AVAIL_ZONE\" | sed -e 's:\([0-9][0-9]*\)[a-z]*\$:\\1:'`"

Current Dockerfile

    FROM node:boron
WORKDIR /usr/src/app
# Install app dependencies
COPY package.json .
RUN npm install
# Bundle app source
COPY . .
CMD [ "npm", "start" ]

How can I read these system variables in the Docker container?

Possible duplicate of [How do I pass environment variables to Docker containers?](https://stackoverflow.com/questions/30494050/how-do-i-pass-environment-variables-to-docker-containers) — juanlumn, Sep 27 '17 at 10:22
@BMitch I cannot run it like that in AWS. I am using ECS service which will handle that. — Naveen Kerati, Sep 27 '17 at 10:26
Which images are you using? You will need to customize your images to be able to do this — Tarun Lalwani, Sep 27 '17 at 10:34
No, I meant to ask you are building the images yourself? Because for doing this you need to have a custom Dockerfile — Tarun Lalwani, Sep 27 '17 at 10:43
Post that Dockerfile and I will see if I can suggest a solution — Tarun Lalwani, Sep 27 '17 at 10:52
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/155414/discussion-between-naveen-kerati-and-tarun-lalwani). — Naveen Kerati, Sep 27 '17 at 10:57

score 1 · Accepted Answer · answered Sep 27 '17 at 11:19

Create a shell script in your project

env.sh

EC2_INSTANCE_ID="`wget -q -O - http://169.254.169.254/latest/meta-data/instance-id || die \"wget instance-id has failed: $?\"`"
test -n "$EC2_INSTANCE_ID" || die 'cannot obtain instance-id'
export EC2_INSTANCE_ID=$EC2_INSTANCE_ID
EC2_AVAIL_ZONE="`wget -q -O - http://169.254.169.254/latest/meta-data/placement/availability-zone || die \"wget availability-zone has failed: $?\"`"
test -n "$EC2_AVAIL_ZONE" || die 'cannot obtain availability-zone'
export EC2_AVAIL_ZONE=$EC2_AVAIL_ZONE
EC2_REGION="`echo \"$EC2_AVAIL_ZONE\" | sed -e 's:\([0-9][0-9]*\)[a-z]*\$:\\1:'`"

Modify your dockerfile to below

FROM node:boron
WORKDIR /usr/src/app
# Install app dependencies
COPY package.json .
RUN npm install
# Bundle app source
COPY . .
COPY env.sh /etc/profile.d/awsenv.sh
ENTRYPOINT ["/bin/sh", "-lc"]
CMD ["env && exec npm start"]

Now when the image starts it will automatically have the environment variables

score 0 · Answer 2 · answered Sep 27 '17 at 10:20

0

Environment variables can be added to a container when running using either the environment option to docker run or through an --env-file option to docker run.

answered Sep 27 '17 at 10:20

yamenk

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How to read system environment variables inside docker container

2 Answers2