Using environment properties with files in elastic beanstalk config files - configuration

Question

Working with Elastic Beanstalk .config files is kinda... interesting. I'm trying to use environment properties with the files: configuration option in an Elastc Beanstalk .config file. What I'd like to do is something like:
files:
"/etc/passwd-s3fs" :
mode: "000640"
owner: root
group: root
content: |
${AWS_ACCESS_KEY_ID}:${AWS_SECRET_KEY}
To create an /etc/passwd-s3fs file with content something like:
ABAC73E92DEEWEDS3FG4E:aiDSuhr8eg4fHHGEMes44zdkIJD0wkmd
I.e. use the environment properties defined in the AWS Console (Elastic Beanstalk/Configuration/Software Configuration/Environment Properties) to initialize system configuration files and such.
I've found that it is possible to use environment properties in container-command:s, like so:
container_commands:
000-create-file:
command: echo ${AWS_ACCESS_KEY_ID}:${AWS_SECRET_KEY} > /etc/passwd-s3fs
However, doing so will require me to manually set owner, group, file permissions etc. It's also much more of a hassle when dealing with larger configuration files than the Files: configuration option...
Anyone got any tips on this?

Answer 1

How about something like this. I will use the word "context" for dev vs. qa.
Create one file per context:
dev-envvars
export MYAPP_IP_ADDR=111.222.0.1
export MYAPP_BUCKET=dev
qa-envvars
export MYAPP_IP_ADDR=111.222.1.1
export MYAPP_BUCKET=qa
Upload those files to a private S3 folder, S3://myapp/config.
In IAM, add a policy to the aws-elasticbeanstalk-ec2-role role that allows reading S3://myapp/config.
Add the following file to your .ebextensions directory:
envvars.config
files:
"/opt/myapp_envvars" :
mode: "000644"
owner: root
group: root
# change the source when you need a different context
#source: https://s3-us-west-2.amazonaws.com/myapp/dev-envvars
source: https://s3-us-west-2.amazonaws.com/myapp/qa-envvars
Resources:
AWSEBAutoScalingGroup:
Metadata:
AWS::CloudFormation::Authentication:
S3Access:
type: S3
roleName: aws-elasticbeanstalk-ec2-role
buckets: myapp
commands:
# commands executes after files per
# http://docs.aws.amazon.com/elasticbeanstalk/latest/dg/customize-containers-ec2.html
10-load-env-vars:
command: . /opt/myapp_envvars
Per the AWS Developer's Guide, commands "run before the application and web server are set up and the application version file is extracted," and before container-commands. I guess the question will be whether that is early enough in the boot process to make the environment variables available when you need them. I actually wound up writing an init.d script to start and stop things in my EC2 instance. I used the technique above to deploy the script.
Credit for the “Resources” section that allows downloading from secured S3 goes to the May 7, 2014 post that Joshua#AWS made to this thread.

Answer 2

I am gravedigging but since I stumbled across this in the course of my travels, there is a "clever" way to do what you describe–at least in 2018, and at least since 2016. You can retrieve an environment variable by key with get-config:
/opt/elasticbeanstalk/bin/get-config environment --key YOUR_ENV_VAR_KEY
And likewise all environment variables with (as JSON or --output YAML)
/opt/elasticbeanstalk/bin/get-config environment
Example usage in a container command:
container_commands:
00_store_env_var_in_file_and_chmod:
command: "/opt/elasticbeanstalk/bin/get-config environment --key YOUR_ENV_KEY | install -D /dev/stdin /etc/somefile && chmod 640 /etc/somefile"
Example usage in a file:
files:
"/opt/elasticbeanstalk/hooks/appdeploy/post/00_do_stuff.sh":
mode: "000755"
owner: root
group: root
content: |
#!/bin/bash
YOUR_ENV_VAR=$(source /opt/elasticbeanstalk/bin/get-config environment --key YOUR_ENV_VAR_KEY)
echo "Hello $YOUR_ENV_VAR"
I was introduced to get-config by Thomas Reggi in https://serverfault.com/a/771067.

Answer 3

I assume that AWS_ACCESS_KEY_ID and AWS_SECRET_KEY are known to you prior to the app deployment.
You can create the file on your workstation and submit it to Elastic Beanstalk instance with the code on $ git aws.push
$ cd .ebextensions
$ echo 'ABAC73E92DEEWEDS3FG4E:aiDSuhr8eg4fHHGEMes44zdkIJD0wkmd' > passwd-s3fs
In .config:
files:
"/etc/passwd-s3fs" :
mode: "000640"
owner: root
group: root
container_commands:
10-copy-passwords-file:
command: "cat .ebextensions/passwd-s3fs > /etc/passwd-s3fs"
You might have to play with the permissions or execute cat as sudo. Also, I put the file into .ebextensions for example, it can be anywhere in your project.
Hope it helps.