How do I pass environment variables to Docker containers

Question

I m new to Docker  and it s unclear how to access an external database from a container  Is the best way to hard-code in the connection string     Dockerfile ENV DATABASE URL amazon rds connection string

User · Answer

If you are using  docker-compose  as the method to spin up your container s   there is actually a useful way to pass an environment variable defined on your server to the Docker container  In your docker-compose yml file  let s say you are spinning up a basic hapi-js container and the code looks like  hapi server    container name  hapi server   image  node image   expose      -  quot 3000 quot   Let s say that the local server that your docker project is on has an environment variable named  NODE DB CONNECT  that you want to pass to your hapi-js container  and you want its new name to be  HAPI DB CONNECT   Then in the docker-compose yml file  you would pass the local environment variable to the container and rename it like so  hapi server    container name  hapi server   image  node image   environment      - HAPI DB CONNECT   NODE DB CONNECT    expose      -  quot 3000 quot   I hope this helps you to avoid hard-coding a database connect string in any file in your container

User · Answer

Using jq to convert the env to JSON   env as json  jq -c -n env  docker run -e HOST ENV   env as json   lt image gt    this requires jq version 1 6 or newer  this pust the host env as json  essentially like so in Dockerfile   ENV HOST ENV   all env from the host as json

User · Answer

Use -e or --env value to set environment variables  default       An example from a startup script    docker run  -e myhost  localhost  -it busybox sh   If you want to use multiple environments from the command line then before every environment variable use the -e flag   Example    sudo docker run -d -t -i -e NAMESPACE  staging  -e PASSWORD  foo  busybox sh      Note  Make sure put the container name after the environment variable  not before that    If you need to set up many variables  use the --env-file flag  For example      docker run --env-file   my env ubuntu bash   For any other help  look into the Docker help      docker run --help   Official documentation  https   docs docker com compose environment-variables

User · Answer

You can pass using -e parameters with docker run    command as mentioned here and as mentioned by  errata   However  the possible downside of this approach is that your credentials will be displayed in the process listing  where you run it   To make it more secure  you may write your credentials in a configuration file and do docker run with --env-file as mentioned here  Then you can control the access of that config file so that others having access to that machine wouldn t see your credentials

User · Answer

docker run --rm -it --env-file  lt  bash -c  env   grep  lt your env data gt    Is a way to grep the data stored within a  env and pass them to Docker  without anything being stored unsecurely  so you can t just look at docker history and grab keys   Say you have a load of AWS stuff in your  env like so   AWS ACCESS KEY  xxxxxxx AWS SECRET  xxxxxx AWS REGION  xxxxxx   running docker with    docker run --rm -it --env-file  lt  bash -c  env   grep AWS    will grab it all and pass it securely to be accessible from within the container

User · Answer

Another way is to use the powers of  usr bin env   docker run ubuntu env DEBUG 1 path to script sh

User · Answer

The problem I had was that I was putting the --env-file at the end of the command docker run -it --rm -p 8080 80 imagename --env-file   env list  Fix docker run --env-file   env list -it --rm -p 8080 80 imagename

User · Answer

Using docker-compose  you can inherit env variables in docker-compose yml and subsequently any Dockerfile s  called by docker-compose to build images  This is useful when the Dockerfile RUN command should execute commands specific to the environment   your shell has RAILS ENV development already existing in the environment  docker-compose yml  version   3 1  services    my-service       build          RAILS ENV is referencing the shell environment RAILS ENV variable        and passing it to the Dockerfile ARG RAILS ENV        the syntax below ensures that the RAILS ENV arg will default to         production if empty         note that is dockerfile  is not specified it assumes file name  Dockerfile       context          args          - RAILS ENV   RAILS ENV -production      environment         - RAILS ENV   RAILS ENV -production   Dockerfile  FROM ruby 2 3 4   give ARG RAILS ENV a default value   production ARG RAILS ENV production   assign the  RAILS ENV arg to the RAILS ENV ENV so that it can be accessed  by the subsequent RUN call within the container ENV RAILS ENV  RAILS ENV   the subsequent RUN call accesses the RAILS ENV ENV variable within the container RUN if    quot  RAILS ENV quot     quot production quot      then echo  quot production env quot   else echo  quot non-production env   RAILS ENV quot   fi  This way  I don t need to specify environment variables in files or docker-compose build up commands  docker-compose build docker-compose up

User · Answer

There is a nice hack how to pipe host machine environment variables to a docker container   env  gt  env file  amp  amp  docker run --env-file env file image name      Use this technique very carefully  because env  gt  env file will dump ALL host machine ENV variables to env file and make them accessible in the running container

User · Answer

We can also use host machine environment variable using -e flag and     Before running the following command  need to export means set  local env variables  docker run -it -e MG HOST  MG HOST -e MG USER  MG USER -e MG PASS  MG PASS -e MG AUTH  MG AUTH -e MG DB  MG DB -t image tag name and version   By using this method  you can set the environment variable automatically with your given name  In my case MG HOST  MG USER  Additionally  If you are using python you can access these environment variable inside docker by import os host username password auth database os environ get  MG HOST   os environ get  MG USER   os environ get  MG PASS   os environ get  MG AUTH   os environ get  MG DB

User · Answer

here is how i was able to solve it  docker run --rm -ti -e AWS ACCESS KEY ID -e AWS SECRET ACCESS KEY -e AWS SESSION TOKEN -e AWS SECURITY TOKEN amazon aws-cli s3 ls   one more example   export VAR1 value1 export VAR2 value2    docker run --env VAR1 --env VAR2 ubuntu env   grep VAR VAR1 value1 VAR2 value2

User · Answer

For Amazon AWS ECS ECR  you should manage your environment variables  especially secrets  via a private S3 bucket  See blog post How to Manage Secrets for Amazon EC2 Container Service   Based Applications by Using Amazon S3 and Docker

User · Answer

You can pass environment variables to your containers with the -e flag   An example from a startup script   sudo docker run -d -t -i -e REDIS NAMESPACE  staging     -e POSTGRES ENV POSTGRES PASSWORD  foo    -e POSTGRES ENV POSTGRES USER  bar    -e POSTGRES ENV DB NAME  mysite staging    -e POSTGRES PORT 5432 TCP ADDR  docker-db-1 hidden us-east-1 rds amazonaws com    -e SITE URL  staging mysite com    -p 80 80   --link redis redis     --name container name dockerhub id image name   Or  if you don t want to have the value on the command-line where it will be displayed by ps  etc   -e can pull in the value from the current environment if you just give it without the     sudo PASSWORD  foo  docker run        -e PASSWORD         If you have many environment variables and especially if they re meant to be secret  you can use an env-file     docker run --env-file   env list ubuntu bash      The --env-file flag takes a filename as an argument and expects each line to be in the VAR VAL format  mimicking the argument passed to --env  Comment lines need only be prefixed with

User · Answer

If you have the environment variables in an env sh locally and want to set it up when the container starts  you could try COPY env sh  env sh COPY  lt filename gt  jar   lt filename gt  jar ENTRYPOINT   quot  bin bash quot     quot -c quot    quot source  env sh  amp  amp  printenv  amp  amp  java -jar   lt filename gt  jar quot    This command would start the container with a bash shell  I want a bash shell since source is a bash command   sources the env sh file which sets the environment variables  and executes the jar file  The env sh looks like this     bin bash export FOO  quot BAR quot  export DB NAME  quot DATABASE NAME quot   I added the printenv command only to test that actual source command works  You should probably remove it when you confirm the source command works fine or the environment variables would appear in your docker logs

[docker] How do I pass environment variables to Docker containers?

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