Accessing environment variables in AWS Beanstalk ebextensions - amazon-web-services

Question

I am trying to access an environment variable that I have defined in the AWS Beanstalk configuration. I need to access it within a config file in .ebextensions or in a file that is copied in place in a config file. I have tried the following:
container_commands:
update_nginx_config:
command: "cp .ebextensions/files/nginx/nginx.conf /etc/nginx/nginx.conf"
And in my nginx.conf file, I have tried to access $MYVAR, ${MYVAR} and {$MYVAR}, some of which was suggested here and here (the latter being directly within a config file).
files:
"/etc/nginx/nginx.conf" :
mode: "000644"
owner: root
group: root
content: |
$MYVAR ${MYVAR} {$MYVAR}
This does not work either. In all cases, the variable names are just output such as $MYVAR, so Beanstalk does not recognize my variables. I found the below in the AWS documentation about container_commands:
They also have access to environment variables such as your AWS
security credentials.
This is great, but it does not say how.
How can I access an environment variable with ebextensions, be it within a config file itself or in a separate file that is copied in place?
Thank you in advance!

Answer 1

I reached out to the Amazon technical support for an answer to this question, and here is their reply:
Unfortunately the variables are not available in ebextensions
directly. The best option to do that is by creating a script that then
is run from container commands like this:
files:
"/home/ec2-user/setup.sh":
mode: "000755"
owner: root
group: root
content: |
#!/bin/bash
# Commands that will be run on container_commmands
# Here the container variables will be visible as environment variables.
container_commands:
set_up:
command: /home/ec2-user/setup.sh
So, if you create a shell script and invoke it via a container command, then you will have access to environment variables within your shell script as follows: $ENVIRONMENT_VARIABLE. I have tested this, and it works.
If you're having issues running a script as root and not being able to read the configured environment variables, try adding the following to the top of your script.
. /opt/elasticbeanstalk/support/envvars
Depending on your use case, you might have to change your approach a bit (at least I did), but it is a working solution. I hope this helps someone!

Answer 2

From this answer: https://stackoverflow.com/a/47817647/2246559
You can use the GetOptionSetting function described here: https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/ebextensions-functions.html
For instance, if you were setting the worker_processes variable, it could look like:
files:
"/etc/nginx/nginx.conf" :
mode: "000644"
owner: root
group: root
content: |
worker_processes `{"Fn::GetOptionSetting": {"Namespace": "aws:elasticbeanstalk:application:environment", "OptionName": "MYVAR"}}`;
Note the backticks `` in the function call.

Answer 3

In case you're using the value directly in a container command, the get-config script that comes with the instance can help.
Example :
20_install_certs:
command: |
MY_VAR=$(/opt/elasticbeanstalk/bin/get-config environment -k MY_VAR)

Answer 4

This is a bit different use-case and be only for debugging purposes.
You can access the environment variables via
$ /opt/elasticbeanstalk/bin/get-config environment
Doc: https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/custom-platforms-scripts.html
Only works for Linux environments I think!