Docker file variable substitution. In this short tutorial, we’ll learn how to pass an environmental variable value into Dockerfile. I've been looking though the docker-compose documentation and have not found anything mentioning this (or any examples online) but it seems like something that would be surprising if not possible. However, Docker does not append the CMD to the entrypoint. However, passing and using them in the Dockerfile isn’t as easy as it could be. /Dockerfile) -t "my-image" . You can workaround that by using env VAR=VALUE in the same line as docker stack deploy : Mar 19, 2024 · Environment variables are a convenient way to externalize application configuration; therefore, they’re also useful for building Docker containers. Sounds very inconvenient having to use the variables without curly brackets, I’m also more used to the curly notation, because it’s clearly readable in most editors and won’t always work using the other type, e. Docker will not expand environment variables inside your Dockerfile. What will we be doing: In this post we will build a simple docker application that returns the environment variable's value to standard out. env file counld be as The env variable substitution would work with a simple . yml Here's a code what's inside a docker-compose file. g SECRET_KEY=198191891. Substitutions are helpful for variables whose value isn't known until build time, or to re-use an existing build request with different variable values. 3 in a custom dockerfile where I copy my template nginx config file Apr 7, 2018 · One of them is using environment variables to store application configuration. Aug 22, 2020 · I take an argument TARGETARCH, assign it to a variable, then change the value of the variable within a RUN command. env file but have not had any luck so far. This issue / feature has been requested a lot from users of Docker, and it looks like the Docker dev team has taken a few passes at implementing the ability to use variable substitution with a env file outside of the working directory. How to use . Docker Compose allows you to define environment variables in several ways, including in the Compose file itself, in separate environment files, or using variable substitution in the Compose file. This file contains the following: jenkins: image: "jenkins:${JENKINS_VERSION}" external_links: - mongodb:mongo ports: - 8000:8080 The image below shows what happens when I try to start everything up. You should choose one method and stick to it, to avoid confusion or possible misconfigurations. env is for variables that are parsed in to the docker-compose. yml (or whatever file you point docker-compose to). 100| to the console. yml before it starts your containers. so, it means we can pass the desired command line parameters through _JAVA_OPTIONS without changing anything on Dockerfile as well as to allow it to be able to start as parent process of container for the valid docker May 9, 2018 · Docker doesn't expand ARG values in the RUN command. 03. 4) does appear to support internal env-file variable substitution. As any values in a Compose file can be interpolated with variable substitution, including compact string notation for complex elements, interpolation is applied before a merge on a per-file basis. This is my current docker-compose. Just create . This file typically contains key-value pairs of environment variables, and it allows you to centralize and manage configuration in one place. yml prometheus - prometheus. env file in your docker-compose. env <docker_image_name> where your . Dec 11, 2023 · I'm struggling with Nginx docker environment variable substitution, it somehow does not work for me. Feb 25, 2018 · You need to use . yml files. the reason why I want to do it, is that the same project is mounted on the same server of “developers” (not in production) and each one has its isolated development environment, I would like to use the same YML file and only change one environment variable, instead of everyone having to modify their YML files Mar 22, 2018 · So docker doesn't know what to do with that, it's just plain text to docker, docker just spews out what you wrote as-is. 25. envfile synax: This file should use the syntax <variable>=value (which sets the variable to the given value) or (which takes the value from the local environment), and # for Oct 17, 2019 · Is there any way to place a variable name as the creation of a network?. This is a snippet from the Dockerfile below: . This is a contrived example nothing something I actually want to do. These variables are not available in your container as environment variables. Jun 8, 2017 · Docker build will always show you the line as is written down in the Dockerfile, despite the variable value. env file in Docker Compose is a text file used to define environment variables that should be made available to Docker containers when running docker compose up. env files in your Compose application. This means that normal shell processing, such as variable substitution, doesn't happen. yml files and would like to specify which env each of them should target. If you want to get a good overview of build-time arguments, environment variables, env_files and docker-compose templating with . In my Dockerfile I have a run command; RUN echo "|${DOCKER_HOST}|", which correctly outputs |192. This works fine and env variables I include via “env_file: . The paths to your . Sep 26, 2022 · This is actually a problem with how you are using the dockerfile. You can combine environment variables and build arguments to allow environment variables to be configured at build-time. Here's my file tree. envfile info for docker run commands and ended up finding the answer elsewhere, but thought I'd share for others: This was key for understanding . (So because I use -- Dec 28, 2020 · EDIT: This answer clearly explains the important difference from defining environment variables in an env file vs using variable substitution in a docker-compose file. env file to dockerfile during build and then pass those args as env variable to container. You can set default values for multiple environment variables, in an . Recommendation To avoid hard-coding values into a Dockerfile, and instead, to dynamically change a setting or custom variable as PYTHONPATH during the build, perhaps the ARG , --build-arg docker features might be most Mar 20, 2018 · When you build the Dockerfile, you get an image. It is not supported when running docker run --env-file . Mar 29, 2022 · I'd like to pass env variables to an yml file which will be used as a config file for a certain container. Important. yml - rules. x of the Compose file format were merged into the Compose Specification. I noticed that the variable assignment in a RUN block behaves differently in buildx. Jan 7, 2019 · Variable substitution in docker-compose. Typical docker-compose file Typical docker-compose file . env” file contents. alertmanager - . And the image has no knowledege about what was written in the Dockerfile. Similar to ARG variables, the statement that defines ENV variables in Dockerfile provides the variable's definition and an optional default value. env file, which is used by docker-compose. env however i have more than one docker-compose. That means, the docker image has no knowledge weather ENV message="Hello, ${name}" or ENV message="Hello, world" was written in the Dockerfile. env && docker-compose up Nov 13, 2019 · When you use an execution list, Docker will interpret the given command literally (without variable expansion). RUN echo dir is $app_dir. Here's the wrapper script #!/bin/env bash # Make sure you have the appropriate token in your ENV variables on a machine that you're running this script on. 12. Grabbing the latest docker-compose release and manually using that version (currently 1. Sep 7, 2019 · I am new to Docker and CI/CD with Gitlab CI/CD. env up -d. That means such a file can not be used directly with Kubernetes/podman anymore and also linters, IDEs, etc. Variable substitution. Instead, it injects the ARG as an environment variable. Aug 6, 2021 · Optionally a name can be given to a new build stage by adding AS name to the FROM instruction. Feb 22, 2016 · docker run --rm --name $image_name -e "app_dir=${image_name}" $image_name. yml docker-compose. Using the exec form doesn't automatically invoke a command shell. I have . if concatenating some pre- and postfixes directly to the variable. env file, but docker stack deploy does not (see the note in Variable substitution section of the Compose file reference). will complain about it. Interpolation applies only to YAML values, not to keys. Dec 18, 2017 · The thing is that it will work if I change the environment variable name to APIPORT, so that it won't have the underscore in it. docker run --env-file . yaml file. docker run --env ZZ_ENVIRONMENT=PROD --env ENV_VAR2=value2 <docker_image_name> If you have a list of environment variables then you can simply create a . env file in folder where docker-compose. yaml is in order to declaring default environment variables for docker-compose. A clear solution is to break them all down to their separate folders but that feels like a last resort solution. Best Option (if it works for you) – Official CLI Arguments. I should also point out I'm using docker machine from a windows host - this configures Jul 4, 2020 · docker --context remote_name stack deploy -c compose-file. instead, Java can read the command line parameters either through the command line or by _JAVA_OPTIONS environment variable. This section covers: How to set environment variables within your container's environment . x and 3. But this variable is not set and is blank within the context of the docker build. Building an in-depth understanding of this topic is the best way to stop struggling and get back to what you actually want to achieve. This file typically contains key-value pairs of variables, and it lets you centralize and manage configuration in one place. DOCKER_BUILDKIT=1 docker build --no-cache -f <(envsubst < . Nov 28, 2020 · sudo snap refresh --edge docker (Version 19. env file, to set values for a pre-processing step for docker-compose. For an example on how to use environment variables for configuring builds, see ENV usage It helps you define a Compose file which is used to configure your Docker application’s services, networks, volumes, and more. yaml stack_name. Options and workarounds. env file with the following content: DIR=/var/www/html Of course you can do that dinamically on each build like: echo "DIR=/var/www/html" > . I'm using nginx version 1. While the same command works perfectly when executed in the Docker Desktop Exec term Nov 24, 2022 · Set ENV Values. So use this variable name a_version : ARG a_version The env_file attribute also lets you use multiple . Jun 14, 2021 · Docker Environment variable not working in CMD Hot Network Questions What was Jesus' issue with Mary touching him after he'd returned to earth after His resurrection? Oct 8, 2023 · I'm encountering an issue with environment variable substitution using the envsubst command within a Dockerfile. env file in Docker Compose is a text file used to define variables that should be made available for interpolation when running docker compose up. env file in the root directory of my Django project which contains my environmental variable e. The shell itself expands the variable, and all of the Linux shells I've used behave differently based on the type of quote. However, because MacOS needs Oct 14, 2021 · Variable substitution in . If you can't change the image at all, you can also configure Compose to pass through values from the host environment Oct 28, 2020 · Since there is no provision to pass substitution variables I am trying to build it with cloud build configuration file (yaml) and then passing the path to the dockerfile in the configuration file. env file to maintain environment-specific variables, docker-compose will substitute your . Docker is taking care of the substitution. env. yml and it hasn't worked. 0. Use substitutions in your build config file to substitute specific variables at build time. You can replace your ENTRYPOINT and CMD to use only this: CMD ["sh", "-c", "ng serve --host ${HOST} --port ${PORT} --disable-host-check"] Mar 7, 2022 · Regarding docker-compose variable substitution, Variable substitution in docker-compose. docker run -d -t my-image $1 And here's the Dockerfile: Dec 3, 2020 · Hi there, I have a docker-compose file where I mount the SSH Authentication Socket as a volume to share the SSH Agent of the host system. Aren't underscores allowed in substituted variable name? I've also tried it by including the variable through environment or env-file in docker-compose. For variables to be set in the container, you will need to specify a . For example, RUN [ "echo", "$HOME" ] won't handle variable substitution for $HOME. Viewed 2k times Jan 21, 2022 · Yes, we could use shell expansion, but in contrast to the Docker Compose file, having placeholders/shell variables inside the YAML makes it an invalid Kubernetes file. Mar 19, 2019 · This is for those looking to pass env variable from docker-compose using . Viewed 3k times Jun 18, 2019 · If you're committing your docker-compose. Substitute with --env-file. We are using environment substitution, so if the environment variable is not provided, we will set a default value of NOT_DEFINED. So ideally speaking these are not environment variables but templating variables. docker-compose uses value from the . Dec 7, 2021 · See 'docker run --help'. The variables that you declare in your env file will be available in your docker-compose file for variable substitution as ${variable_name}. env file and then pass the file as an argument in the CLI. . Feb 7, 2020 · Though having read the Docker documentation about environment variables I have some trouble understanding the variable substitution. If you want to expand variables, you need to use a shell in your CMD. This is the cloud build configuration file where I need to pass 5 variables for the Dockerfile to consume and the yaml file goes like this: Sep 3, 2020 · Variable substitution in . 27. You can't override or set an environment variable at build-time. yml file when running docker-compose with sudo. The name can be used in subsequent FROM and COPY --from=<name> instructions to refer to the image built in this stage. env file, specified in the env_file attribute, are relative to the location of your compose. 99. vars or whatever your file name is that contains the variables. env file and add all the varibales into it and in the docker run command can refer the env file as below. The template is nothing but the nginx configuration file with one/more variables which require substitution with some value. 8) Ask Question Asked 1 year, 7 months ago. 13)Still seems to contain docker-compose 1. 100. May 15, 2020 · So the problem does not have a "direct" solution, but if the variable you would like to substitute will be used, in the end, in some shell command (in a RUN, ENTRYPOINT or CMD directive), you could just as well keep the initial value as is (with no substitution), then substitute it later on? Before using environment variables, read through all of the information first to get a full picture of environment variables in Docker Compose. Users can provide values later via the command line or Docker Compose. Feb 24, 2017 · I want to create a Docker Image that acts as an executable for which the user passes a token as an environment variable. I would like to define one variable in the file and then use it in other variables: APP_ENV=dev-foo LOCALPATH=/tmp/ I am trying to perform variable substitution inside of a . env file. 5 and does not perform env-file substitution. Modified 1 year, 7 months ago. Feb 1, 2023 · Basic string variable substitution in docker-compose files (3. First of all sorry for the late reply. Sep 10, 2024 · Use default substitutions or define your own substitutions. The relevant part of my Dockerfile looks like this: Apr 25, 2024 · How does the variable substitution happen ? We will create a template in some folder ,say folder-A. env variables into docker-compose. In the . docs. yml using env_file: . Dec 1, 2016 · I am having trouble creating and using variables in a Dockerfile - I build a Docker image via a Dockerfile with this command: $ docker build --build-arg s=scripts/a. Ask Question Asked 4 years ago. I have edited my answer for clarity but please make sure you also understand the other answer. Aug 9, 2021 · docker-compose --env-file dev. Legacy versions 2. The executable has sub commands that the user should pass via dockers CMD (think of git with authentication via Env). yml file. web” are correctly used in the deployment. env files is a Docker Compose CLI feature. Interpolation in . yml to revision control and want to use a separate untracked . Feb 8, 2016 · I am using docker-compose and I want my env_file to have variable subsitution. yml file when running docker-compose with sudo 0 Passing in environment variables into docker file that is build via a compose yaml Sep 28, 2023 · This includes how you handle environment variables. Steps to reproduce the issue: Set an environment variable on the system running docker compose e. I am on Docker version 19. g. 168. However, I’d like to make use of docker-compose variable substitution to change a couple of items in the yaml based on an “. env file for docker run --env-file. yml: version: '3' services: The env_file attribute also lets you use multiple . Dec 10, 2020 · The computed value will not be visible in debugging tools like docker inspect or docker exec, but the main container process will still see it. export MY_VAR=foo; Reference the environment variable in an . sh -t a . yml interpreter, not for the container. When building a Docker image from the commandline, you can set those values using –build-arg: $ docker build --build-arg some_variable_name=a_value. env - alertmanager. env file I set DOCKER_HOST=192. Values for environment variables must be declared in the Dockerfile. Jan 25, 2019 · Docker Compose automatically loads . The nginx docker image has a function which will read this template file and execute the envsubst command on the template Mar 1, 2016 · I'm currently trying to use variable substitution in a docker-compse. env e. Dollar-notation variables like $HI are substituted in the docker-compose. env files does not work when using docker compose v2. env files that are in a different directory than a docker-compose YML file, with variable substitution and relative paths. You need to pass the environment value as a build argument in the docker build command then use the ARG keyword inside the Dockerfile. Jan 7, 2019 · I define the DOCKER_HOST arg in an . Jun 19, 2016 · Came here looking for . env files - head over to this in-depth guide about ENV and ARG variables in Docker. Modified 2 years, 10 months ago. (1) Rather than starting with just the names of the environment variables, and then trying to get the corresponding values, it might be easier to run env and get the names and the values together. MY_CONTAINER_VAR="${MY_VAR}" and use MY_CONTAINER_VAR as a environment variable in docker Feb 2, 2024 · Compose file Substitute with an . An . jihzezuvulodhoeeqwmomuebzbqpqgvedjymfsdvzwmv
