Docker file variable substitution

Docker file variable substitution. Name the variables however you want since we’ll only access their values. However, Docker does not append the CMD to the entrypoint. Cheers, P. env files - head over to this in-depth guide about ENV and ARG variables in Docker. 4) the build argument does not seem to expand as expected. The env_file attribute also lets you use multiple . 99. 9590. 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" > . env variables into docker-compose. The shell itself expands the variable, and all of the Linux shells I've used behave differently based on the type of quote. With this compose file: test. 6 days ago · Use default substitutions or define your own substitutions. env file: Sep 7, 2019 · I am new to Docker and CI/CD with Gitlab CI/CD. I have edited my answer for clarity but please make sure you also understand the other answer. The executable has sub commands that the user should pass via dockers CMD (think of git with authentication via Env). alertmanager - . yaml stack_name. Mar 1, 2016 · I'm currently trying to use variable substitution in a docker-compse. 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/ 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. However, passing and using them in the Dockerfile isn’t as easy as it could be. You should choose one method and stick to it, to avoid confusion or possible misconfigurations. sh . zip" SHELL ["powershell", "-command"] # This works, ${azureArchive} is Jun 20, 2016 · Variable substitution in your docker-compose. 25. sh instead of ENTRYPOINT ["/entrypoint. The env variable substitution would work with a simple . Jun 18, 2019 · If you're committing your docker-compose. This is my current docker-compose. yml up 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. 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. : ${PORT} and add it to the name of the service so the same compose file could be used without sed or any custom script. sh as ENTRYPOINT. env file in the root directory of my Django project which contains my environmental variable e. yml interpreter, not for the container. I change "/" to be ":" and get it worked. Nov 29, 2016 · I am attempting to consume ARG or ENV variables from a RUN or CMD statement on Docker in Windows Server 2016, but no matter what I try, the variable is never interpolated. If you can't change the image at all, you can also configure Compose to pass through values from the host environment 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. If unspecified, BuildKit uses a bundled version of the Dockerfile frontend. Viewed 3k times 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. I noticed that the variable assignment in a RUN block behaves differently in buildx. Feb 17, 2023 · You must create . In this short tutorial, we’ll learn how to pass an environmental variable value into Dockerfile. Sep 3, 2015 · The problem is I need to attach host Docker binaries, but I don't know exact path of docker on target system, on some it could be /bin/docker, on others - /usr/local/bin/docker, etc. /Dockerfile) -t "my-image" . Compose file 2. env file but have not had any luck so far. Feb 2, 2024 · Compose file Substitute with an . Instead, it injects the ARG as an environment variable. 1. The . You can reference the filename, which is parsed to extract the environment variables to set: $ docker run --env-file=env_file_name alpine env With docker-compose. docs. – Emil Commented Nov 8, 2019 at 11:37 Sep 3, 2020 · Variable substitution in . We are using environment substitution, so if the environment variable is not provided, we will set a default value of NOT_DEFINED. env variables not substituted in docker file. DOCKER_BUILDKIT=1 docker build --no-cache -f <(envsubst < . Jun 15, 2016 · Then when running the command docker-compose up it will result in a docker run that is configured for the machine you're working on. 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. Variables available in your container are a combination of values found in your env_file files and values described in the environment section of the service. yml docker-compose. First of all sorry for the late reply. In the . env file. 168. If you have specified a Compose file with docker-compose -f FILE, paths in env_file are relative to the directory that file is in. env file: STARTDATE=value Add environment variable directly to build machine with command; For linux. web” are correctly used in the deployment. I post the result in here. env <docker_image_name> where your . Mar 7, 2022 · Regarding docker-compose variable substitution, Variable substitution in docker-compose. env file, which is used by docker-compose. env - alertmanager. Obviously it wasn't possible so I wanted to use az environment variable e. Users can provide values later via the command line or Docker Compose. 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. env if it is substituted with --env-file. Feb 25, 2018 · You need to use . 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. Sep 28, 2023 · This includes how you handle environment variables. May 9, 2018 · Docker doesn't expand ARG values in the RUN command. Jul 11, 2019 · Looks like Thanos gives this out of the box. env e. For example, say I have this line in my Dockerfile: FROM myApp What I want is this: FROM myApp:${VERSION} This way I can say docker build . env file can be overridden by another . Modified 1 year, 6 months ago. <src> may contain wildcards and matching will be done using Go’s filepath. Results in: PS E:\myproject> docker build -t cmd . Can be a single value or a list. In entrypoint. env file and add all the varibales into it and in the docker run command can refer the env file as below. ServiceFabric. env file cannot be used? Aug 7, 2023 · I need to pass env variable from file to a command in a docker-compose but it seems impossible. However, note that if we want to change the environment variables we need to re-run docker compose again because the env values are placed in the container with the env_file attribute in docker-compose. md How to declare default values for environment values substitution in situations where the . 100. 5. instead, Java can read the command line parameters either through the command line or by _JAVA_OPTIONS environment variable. Provide details and share your research! But avoid …. yml - rules. ENV env_name John. You can declaratively do that in the Docker Compose file. yaml file. We have to configure Thanos to watch for the config file which has this templated variables and produce the output to a directory. 4+). env” file contents. env && docker-compose up By leveraging environment variables and interpolation in Docker Compose, you can create versatile and reusable configurations, making your Dockerized applications easier to manage and deploy across different environments. Asking for help, clarification, or responding to other answers. 3. I should also point out I'm using docker machine from a windows host - this configures Feb 1, 2023 · Basic string variable substitution in docker-compose files (3. The following syntax rules apply to environment files: Lines beginning with # are processed as comments Jun 8, 2017 · Docker build will always show you the line as is written down in the Dockerfile, despite the variable value. 03. Here's my file tree. x compose files. yml: version: '3' services: Feb 19, 2019 · When you set the same environment variable in multiple files, here’s the priority used by Compose to choose which value to use: 1. Example of . The paths to your . Conclusion. 1. (So because I use -- Jan 25, 2019 · Docker Compose automatically loads . yml file when running docker-compose with sudo. docker run --env-file . Jan 7, 2019 · I define the DOCKER_HOST arg in an . Since your Compose file requires PGPASSWORD to be Dec 7, 2021 · See 'docker run --help'. Jun 19, 2016 · Came here looking for . The result of this Dockerfile is that second and third lines are considered a single instruction: FROM microsoft/nanoserver COPY testfile. In Azure DevOps I have two pipelines. env files in your Compose application. yml -f docker-compose. So use this variable name a_version : ARG a_version Aug 6, 2021 · Optionally a name can be given to a new build stage by adding AS name to the FROM instruction. I'm using nginx version 1. The same problem you have is when putting environment variables in docker-compose and expect them to be available during building-phase with Dockerfile (in the build-stage of docker-compose). But Apr 12, 2016 · I am wondering if a env variable can be used in a docker from? Reason for this is to control the tagging. 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. export CLI=random on your host then docker exec -it <your_container> ${CLI} do something without quotes will substitute ${CLI} with the Apr 1, 2018 · In the docker-compose file, you can have variables substitution based on environment variables. We are substituting variables in ENTRYPOINT in order to read the environment variables passed at docker run. Dec 21, 2017 · I am trying to use variable substitution in a docker-compose. Best Option (if it works for you) – Official CLI Arguments. 0. We can declare and assign variables in our . 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. Legacy versions 2. Use substitutions in your build config file to substitute specific variables at build time. Just create . The name sounds like a . yml Here's a code what's inside a docker-compose file. It is a convenient way to pass many environment variables to a single command. You can fix this in a number of ways: You can just write it as a plain string instead, as in: Aug 26, 2021 · It looks like the environment variables in the docker-compose are not available at the time of creating the container with the docker-compose. yml version: "2. It is not supported when running docker run --env-file . yaml. You can workaround that by using env VAR=VALUE in the same line as docker stack deploy : Mar 20, 2018 · When you build the Dockerfile, you get an image. env file, but docker stack deploy does not (see the note in Variable substitution section of the Compose file reference). env file and put it to the docker-compose root directory. The simplest way to pass an environment value is to hardcode it in the Dockerfile. That means, the docker image has no knowledge weather ENV message="Hello, ${name}" or ENV message="Hello, world" was written in the Dockerfile. conf. I the matter is on delimiter. If <src> is a file or directory, then they must be relative to the source directory that is being built (the context of the build). Hardcoding Environment Values. x of the Compose file format were merged into the Compose Specification. If you can use 3. env. yml file should be. You can get similar behaviour with custom files names if you change a few things in your docker-compose command: docker-compose -f docker-compose. sh we substitute variables and run nginx. yml. However, because MacOS needs Nov 13, 2019 · When you use an execution list, Docker will interpret the given command literally (without variable expansion). yml to set the number of CPUs. Add environment variables from a file. However, I’d like to make use of docker-compose variable substitution to change a couple of items in the yaml based on an “. Here’s my . While the same command works perfectly when executed in the Docker Desktop Exec term Mar 19, 2019 · Now when you run docker-compose up -d command, docker-compose file takes values from . yml to revision control and want to use a separate untracked . Nov 12, 2019 · Dockerfile ENV variable substitution into another ENV variable. Steps to reproduce the issue: Set an environment variable on the system running docker compose e. Take this Dockerfile for example: FROM microsoft/windowsservercore ARG azureArchive="Microsoft. 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?. Sending build context to Docker daemon 3. env file in your working directory that contains DOCUMENT_ROOT=. An env_file, is a term for a file containing lines about environment variables which are usable by the Docker CLI. yml up Jun 5, 2019 · Hi There, I have this question going on Stackoverflow, I would copy/paste it here, but I’ve already added some comments to it that are interesting. 311. Oct 14, 2021 · Variable substitution in . env_file. Now Dockerfile of web containes all those varibales through args during build. Viewed 2k times Mar 22, 2021 · Reducing Docker Layers Jun 29, 2020 · 5 min read. Interpolation applies only to YAML values, not to keys. This file typically contains key-value pairs of environment variables, and it allows you to centralize and manage configuration in one place. You can replace your ENTRYPOINT and CMD to use only this: CMD ["sh", "-c", "ng serve --host ${HOST} --port ${PORT} --disable-host-check"] (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. Modified 2 years, 10 months ago. 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. If you want to get a good overview of build-time arguments, environment variables, env_files and docker-compose templating with . 12. 2 cpus: ${ Jul 9, 2018 · Thanks all. 5. I have . And Prometheus then picks this file as its config file. Docker Compose will automatically read environment variables from a . sh"] we wouldn’t be able to environment variables at Jul 16, 2018 · The env_file key (likewise for the environment key) is used to set environment variables for use inside the container only. The relevant part of my Dockerfile looks like this: 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. Substitution from . yml file. Jan 27, 2020 · In my projects Docker file I have some environment variables, like this: ENV ACCEPT_EULA=Y ENV SA_PASSWORD=Password ENV MSSQL_PID=Developer ENV MSSQL_TCP_PORT=1433 And I would like to pass the password here as an environment variable set in my pipeline. This is a contrived example nothing something I actually want to do. This works fine and env variables I include via “env_file: . I am on Docker version 19. env file counld be as Copies new files, directories, or remote file URLs from <src> and adds them to the filesystem of the image at the path <dest>. For the few places where keys are actually arbitrary user-defined strings, such as labels or Docker is taking care of the substitution. docker run -d -t my-image $1 And here's the Dockerfile: The file above is called env_file_name (name arbitrary) and it’s located in the current directory. Reducing the size of your Docker images is important for a number of reasons, and while there are newer tools such as multi-stage builds, reducing the number of layers in your image may help. vars or whatever your file name is that contains the variables. /, then you can use the local . local . env however i have more than one docker-compose. export STARTDATE=value For Windows. volumes: - $(which docker):/bin/docker into docker-compose. env file in your docker-compose. myApp --build-arg VERSION=9. Similar to ARG variables, the statement that defines ENV variables in Dockerfile provides the variable's definition and an optional default value. Example: 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 . 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 Aug 22, 2020 · I take an argument TARGETARCH, assign it to a variable, then change the value of the variable within a RUN command. For variables intended to be interpolated within the docker-compose. It is not supported by Swarm when running docker stack deploy. . Feb 7, 2020 · Though having read the Docker documentation about environment variables I have some trouble understanding the variable substitution. env file then pass it to docker-compose file. That can be achieved with the --build-arg param. Step 1/2 : FROM microsoft/nanoserver. And the image has no knowledege about what was written in the Dockerfile. Running that command, with the above Dockerfile, will result in the following line being printed in the process: Mar 19, 2024 · There are two different ways to do it. Azure. 2" services: neo4j: image: neo4j:3. Important. In this training, you will learn the difference between exec and shell form concerning variable substitution. Jan 7, 2019 · Variable substitution in docker-compose. Feb 22, 2016 · Notice that you are using the variable inside the Dockerfile. env files does not work when using docker compose v2. g SECRET_KEY=198191891. Setting ARG and ENV values leaves traces in the Docker image. env is for variables that are parsed in to the docker-compose. Declaring a syntax version lets you automatically use the latest Dockerfile version without having to upgrade BuildKit or Docker Engine, or even use a custom Dockerfile implementati Jun 20, 2018 · File: compose/environment-variables. MY_CONTAINER_VAR="${MY_VAR}" and use MY_CONTAINER_VAR as a environment variable in docker Apr 7, 2018 · One of them is using environment variables to store application configuration. sh -t a . Aug 3, 2019 · How do I replace placeholders in a file with variables from another file? (Like docker-compose is doing it. export MY_VAR=foo; Reference the environment variable in an . env file to maintain environment-specific variables, docker-compose will substitute your . Your . 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? I am trying to perform variable substitution inside of a . This is documented under Variable Substitution. Variable is not defined In the example below, we set the same environment variable on an Environment file, and the Compose file: It helps you define a Compose file which is used to configure your Docker application’s services, networks, volumes, and more. if concatenating some pre- and postfixes directly to the variable. env files is a Docker Compose CLI feature. env file, specified in the env_file attribute, are relative to the location of your compose. 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 Nov 24, 2022 · Set ENV Values. 4+ compose files, extension fields are probably the best option: Sep 17, 2019 · If you specify DOCUMENT_ROOT as a variable in the docker compose file. In some cases, this is good enough. 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. Environment file Dockerfile 4. env file by running. yml before it starts your containers. 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. Jul 4, 2020 · docker --context remote_name stack deploy -c compose-file. yaml is in order to declaring default environment variables for docker-compose. I need to pass an environment variable as LABEL in Dockerfile, my Dockerfile looks like below: FROM nginx LABEL maintainer="blabla" ENV GROUP="default" #Checking if Label values can be set from ENV Variables LABEL group="${GROUP}" below command to pass the build and run the docker file env variable: docker build -t nginx:test_label . yml file will be pulled (in decreasing order of priority) from your shell's environment and your . ) I found many articles about single variable replacements or replacement by environment Dec 1, 2023 · This command runs envsubst against our template file and then reloads our Nginx container with an updated conf iguration. An . Navigate to the folder 10_shell-vs-exec-form-variable-substitution from CLI, before you get started. Ask Question Asked 4 years ago. I want to have cross-platform solution, just putting something like this. g. yml and it hasn't worked. environment: - WORKING_DIR=${DOCUMENT_ROOT} And have an . yml file when running docker-compose with sudo 0 Passing in environment variables into docker file that is build via a compose yaml Nov 16, 2020 · Create . will complain about it. The name can be used in subsequent FROM and COPY --from=<name> instructions to refer to the image built in this stage. If we have used RUN /entrypoint. This file would have the "substituted values" already from Thanos sidecar. yml files, we just reference a env_file, and Docker parses it for the variables to set. Sep 13, 2023 · In docker file we run entrypoint. docker-compose -f /path/to/docker-compose. 100| to the console. Interpolation in . Shell environment variables 3. If you could shed some light onto this one, here or on stack, I’ll appreciate and cross-post where applicable. Let’s hardcode John as a default name in our Dockerfile: FROM alpine:latest. For variables to be set in the container, you will need to specify a . When executed without an explicit --env-file flag, Compose searches for an . If you want to expand variables, you need to use a shell in your CMD. That means such a file can not be used directly with Kubernetes/podman anymore and also linters, IDEs, etc. . yml using env_file: . env file for docker run --env-file. WindowsServer. In my Dockerfile I have a run command; RUN echo "|${DOCKER_HOST}|", which correctly outputs |192. Environment variables declared in the environment section override these values – this holds true even if those values are empty or Dec 11, 2023 · I'm struggling with Nginx docker environment variable substitution, it somehow does not work for me. yml file, they have to come from the host machine in one of the following ways: Apr 26, 2017 · You can then pass in the variable like you normally would between the strings and that would give you the readability of heredocs and still be able to use Docker variables. replace ENV values of Dockerfile at runtime. Mar 19, 2024 · Environment variables are a convenient way to externalize application configuration; therefore, they’re also useful for building Docker containers. A clear solution is to break them all down to their separate folders but that feels like a last resort solution. This file contains the following: jenkins: image: "jenkins:${JENKINS_VERSION}" external_links: - mongodb:mongo ports: - 8000:8080 The image below shows what happens when I try to start everything up. Jan 31, 2019 · @Ben my answer to your question of ~"if it's possible" is no, I don't believe so on the basis that the environment variables specified after the docker exec command appear to be evaluated on the host, e. 3 in a custom dockerfile where I copy my template nginx config file Dec 29, 2022 · There is a nice hack how to pipe host machine environment variables to a Docker container: env > env_file && docker run --env-file env_file image_name Use this technique very carefully, because env > env_file will dump ALL host machine ENV variables to env_file and make them accessible in the running container. yml prometheus - prometheus. 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: Apr 18, 2017 · This might have worked previously, but with current docker version (19. env file versus . env file in your working directory ( PWD) and loads values both for self-configuration and interpolation. 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 . Jul 1, 2024 · Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand Thanks for contributing an answer to Stack Overflow! Please be sure to answer the question. Use the syntax parser directive to declare the Dockerfile syntax version to use for the 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. 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. env file if it's available. The Docker Compose documentation pages are quite extensive and include a full reference for the Docker Compose file format. 072 kB. 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. COPY greetings. That variable will be evaluated at build time (docker build), so you need to pass its value at that moment. Other ways to go are: Extension fields (compose file 3. 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 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. env files at the root of your project, which is also where your docker-compose. Aug 19, 2016 · We have an infrastructure where we wanted to deploy compose apps with the same service name but different container name. x and 3. The process to build docker images for this app is the same. 8) Ask Question Asked 1 year, 6 months ago. 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. env file, but they are not the same. env file can also be used to declare pre-defined environment variables used to control Compose behavior and files to be loaded. Match rules. Jun 14, 2021 · That means no i/o redirection, no wildcard processingand no variable expansion. I am sure there are other methods with more extensive escapes with single-ticks, but I also prefer a solution that is easy to read and use in case others need to manage it. env file I set DOCKER_HOST=192. 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 in folder where docker-compose. Oct 6, 2020 · The extends option can be nice but it's not supported in 3. Oct 8, 2023 · I'm encountering an issue with environment variable substitution using the envsubst command within a Dockerfile. txt c:\\ RUN dir c:\. So I try first with environment var but it doesn't work again. Changing your example, it would be: 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. env file syntax. Feb 8, 2016 · I am using docker-compose and I want my env_file to have variable subsitution. setx STARTDATE value After that in docker-compose you need to use this value. In "Step 65/78", I print the script content and "Step 67/78" run the script well. yml files and would like to specify which env each of them should target. kdoq ggdxoe rotlyfc zinodv ljvf vbux dvnti vhcnfq wbkdt uluh