I want to let my application know which image version it is running on.
The idea was to pass the Docker image tag into the image as an environment variable. However I don't want to change the version number in both the image line AND in the ENV variable line all the time.
Example:
version: "3"
VERSION=0.2.3
services:
app:
image: myimage:$VERSION
environment:
- APPLICATION_VERSION:$VERSION
Is it possible to declare variables in order to update all values together or is there any other solution available?
You cannot define $VERSION inside the docker-compose.yml.
You have two options for this:
define it in a .env file
send as a command line argument when you run the docker-compose command. e.g. VERSION=0.2.3 docker-compose up -d
Related
I have a Dockerfile that has access to a variable that indicates the environment it is being targeted to. Our CICD pipeline makes this environment variable available to the Dockerfile and I can test for a particular environment using "Run if $Environment =".
When I detect a "test" environment, I need to create another environment variable on-the-fly. However, code like this doesn't seem to work:
RUN if $Environment="test" ; then ; /
ENV NewEnvironmentVariable = "test" ; /
fi
The get "ENV" not found when it runs. So obviously, you can't use ENV this way within a RUN .. if.
I CAN however, use bash commands to export the variable, but it's probably creating this export in a different context, so, the Dockerfile doesn't have access to it. I would have thought that exporting it would make the new environment variable to the Docker file (when it returns from the "if" block.
In short, I simply need to evaluate and existing environment variable and if it contains the value I'm looking for it will create a new ENV variable just as if I have done "ENV MyNewVar=1".
Is this possible?
Thanks
Am using drone docker plugin to build and publish docker images, while building the docker image, i want refer some of the env variables exposed by Drone in drone docker plugin repo and tags parameters.
What is needed
repo = first three characters of DRONE_COMMIT_BRANCH variable value - like ${DRONE_COMMIT_BRANCH:0:3}, not working
tags = first seven characters of DRONE_COMMIT_SHA variable value, like ${DRONE_COMMIT_SHA:0:7}, working
image = should be according to above repo and tags like,
Eg:- image: registry/repo:tag
image: registry/${DRONE_COMMIT_BRANCH:0:3}:${DRONE_COMMIT_SHA:0:7}
Concerns
I can use any env variable exposed by Drone for such purpose, or only
specific is only can be used?
drone docker plugin repo parameter supports env variable
expansion and string manipulation, as supported by tags
parameter?
image parameter support variable expansion and string manipulation?
Drone YAML file
Please suggest me how to achieve this use case?
Thanks in advance.
Having a Spring Boot application we are using application.yml file to store properties. I got a task to give a user a possibility to override some properties while starting an application. Taking into consideration we have dockerised our app docker-compose file is the very right place I believe for that. I found one option which works actually, env_file:
backend:
build:
context: backend
dockerfile: Dockerfile.backend
restart: always
ports:
- 3000:3000
env_file:
- backend/custom.env
volumes:
- ../m2_repo:/root/.m2/
- ../{APP_NAME}/data_sources:/backend/data_sources/
links:
- database
networks:
main:
aliases:
- backend
This solves perfectly my task and all the KEY=VALUE pairs override existing in application.yml properties. However, I have 2 questions:
It appeared that having multiple services in my docker-compose file I need specify a separate env_file for each service, which is probably not very convenient. Is there a possibility to have one common env_file for the whole docker-compose file?
I know that for docker-compose run command there is an option -e where i can put key=value pairs of env variables. Is there any similar option for docker-compose up? I mean in order not to use env_file at all.
Ad 1: It is not possible. I also believe it is intentional - to make the developer define what container has access to what .env data.
Ad 2: No, you cannot supply the variables using a runtime parameter of up command of docker-compose (run docker-compose help up to see the available runtime params). But you can define these using environment clause from within a compose file, like:
restart: always
ports:
- 3000:3000
env_file:
- backend/custom.env
environment:
- DB_PASSWORD # <= #1
- APP_ENV=production # <= #2
ie.
either just a name of the env var - its value is then taken from the host machine
or the whole definition to create a new one to be available within a container
See docs on environment clause for more clarification.
Another thing you can do in order to override some settings is to extend the compose file using a "parent" one. Docs on extends clause
Unfortunately as of now, extends won't work when using compose file of version 3, but it is being discussed in this github issue, so hopefully it will be available soon:)
I made an application and I need to test it on our lab. My colleague has done a docker-compose.yml file but nobody is at office today and I'm lost with a line in this file:
image: gitlab-${DOCKERADM_ENV}:5005/rims/mgmt-docker-gui:lab
Because when I do docker-compose -f docker-compose-mgmt.yml pull I have an error DOCKERADM_ENV is not set.
I want to set this variable but how can I do that ?
It's read from environment variables, so you can use:
DOCKERADM_ENV=<value> docker-compose -f docker-compose-mgmt.yml pull
Try setting environment variable
For windows ,
SET DOCKERADM_ENV=boo
For OS X or Linux:
export DOCKERADM_ENV=boo
In my Dockerfile, I would like to define variables that I can use later in the Dockerfile.
I am aware of the ENV instruction, but I do no want these variables to be environment variables.
Is there a way to declare variables at Dockerfile scope?
You can use ARG - see https://docs.docker.com/engine/reference/builder/#arg
The ARG instruction defines a variable that users can pass at
build-time to the builder with the docker build command using the
--build-arg <varname>=<value> flag. If a user specifies a build
argument that was not defined in the Dockerfile, the build outputs an
error.
Can be useful with COPY during build time (e.g. copying tag specific content like specific folders)
For example:
ARG MODEL_TO_COPY
COPY application ./application
COPY $MODEL_TO_COPY ./application/$MODEL_TO_COPY
While building the container:
docker build --build-arg MODEL_TO_COPY=model_name -t <container>:<model_name specific tag> .
To answer your question:
In my Dockerfile, I would like to define variables that I can use later in the Dockerfile.
You can define a variable with:
ARG myvalue=3
Spaces around the equal character are not allowed.
And use it later with:
RUN echo $myvalue > /test
To my knowledge, only ENV allows that, as mentioned in "Environment replacement"
Environment variables (declared with the ENV statement) can also be used in certain instructions as variables to be interpreted by the Dockerfile.
They have to be environment variables in order to be redeclared in each new containers created for each line of the Dockerfile by docker build.
In other words, those variables aren't interpreted directly in a Dockerfile, but in a container created for a Dockerfile line, hence the use of environment variable.
This day, I use both ARG (docker 1.10+, and docker build --build-arg var=value) and ENV.
Using ARG alone means your variable is visible at build time, not at runtime.
My Dockerfile usually has:
ARG var
ENV var=${var}
In your case, ARG is enough: I use it typically for setting http_proxy variable, that docker build needs for accessing internet at build time.
Christopher King adds in the comments:
Watch out!
The ARG variable is only in scope for the "stage that it is used" and needs to be redeclared for each stage.
He points out to Dockerfile / scope
An ARG variable definition comes into effect from the line on which it is defined in the Dockerfile not from the argument’s use on the command-line or elsewhere.
For example, consider this Dockerfile:
FROM busybox
USER ${user:-some_user}
ARG user
USER $user
# ...
A user builds this file by calling:
docker build --build-arg user=what_user .
The USER at line 2 evaluates to some_user as the user variable is defined on the subsequent line 3.
The USER at line 4 evaluates to what_user as user is defined and the what_user value was passed on the command line.
Prior to its definition by an ARG instruction, any use of a variable results in an empty string.
An ARG instruction goes out of scope at the end of the build stage where it was defined.
To use an arg in multiple stages, each stage must include the ARG instruction.
If the variable is re-used within the same RUN instruction, one could simply set a shell variable. I really like how they approached this with the official Ruby Dockerfile.
You can use ARG variable defaultValue and during the run command you can even update this value using --build-arg variable=value. To use these variables in the docker file you can refer them as $variable in run command.
Note: These variables would be available for Linux commands like RUN echo $variable and they wouldn't persist in the image.
Late to the party, but if you don't want to expose environment variables, I guess it's easier to do something like this:
RUN echo 1 > /tmp/__var_1
RUN echo `cat /tmp/__var_1`
RUN rm -f /tmp/__var_1
I ended up doing it because we host private npm packages in aws codeartifact:
RUN aws codeartifact get-authorization-token --output text > /tmp/codeartifact.token
RUN npm config set //company-123456.d.codeartifact.us-east-2.amazonaws.com/npm/internal/:_authToken=`cat /tmp/codeartifact.token`
RUN rm -f /tmp/codeartifact.token
And here ARG cannot work and i don't want to use ENV because i don't want to expose this token to anything else