Retrieving the environment variables from the Docker container and using it in the Jenkins pipeline

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Hello everyone!

I have a question regarding accessing sensitive data that are stored as environment variables in a Docker container to use those in a Jenkins pipeline.

Generally, I have built a custom image in Docker based on the jenkins/jenkins official image. Initially, when I was running the docker image to create a docker container, I passed environment variables there and I’m able to view them in the container via Docker CLI.

I’ve attempted to do so far:

pipeline {
    agent any
    tools {
        'org.jenkinsci.plugins.docker.commons.tools.DockerTool' 'docker'
    }

stage('Run Docker Container') {
                steps {
                    script {
                        def myContainer = docker.image('my_custom_image:0.1')
                        def var1Value = myContainer.inside {
                            sh(script: 'echo $Key', returnStdout: true).trim()
                        }
                        echo "The value of Key is: ${var1Value}"
                    }
                }
    }

Although I am aware that this script does not provide much value in a pipeline. I assume that it should be something with docker(my_custom_image).run, but I couldn’t find the correct script.

However, I found a way of retrieving the value of environment variables by using global credentials, particularly secret text which has been working for me, I still looking for a solution to implement the initial idea there though.

I would appreciate any advice or tips that help me to figure this out.

2

Hello @vitaliizghonnik,

I’m not entirely sure if I understood everything correctly, but let’s give it a try. You want to retrieve the environment variable from the Docker container and use it in your Jenkins pipeline, correct?

One approach could be to run a command inside the Docker container that prints the value of the environment variable, and then capture the output of that command. However, I’m not entirely comfortable with this approach.

Here’s a possible modification you could make to your pipeline script:

pipeline {
    agent any
    tools {
        'org.jenkinsci.plugins.docker.commons.tools.DockerTool' 'docker'
    }

    stages {
        stage('Run Docker Container') {
            steps {
                script {
                    def myContainer = docker.image('my_custom_image:0.1')
                    myContainer.run()
                    def var1Value = sh(script: 'docker exec <container_id> /bin/sh -c "echo $Key"', returnStdout: true).trim()
                    echo "The value of Key is: ${var1Value}"
                }
            }
        }
    }
}
3

Hello @poddingue,
Thank you for your prompt response and willingness to assist me in making it work.

Yes, you understood me correctly. Sorry, I should mention it initially, but I didn’t install Docker inside my custom Docker image but instead was supposed to use the Docker Plugin available in Jenkins for that reason.

Also, the way how I passed environment variables to the Docker container was the following command: docker run -e Key=$Key

I’m right now writing that message as I tried to implement the proposed solution, and it gave me the following response:

+ docker run -d my_custom_image:0.1

/var/jenkins_home/workspace/Jenkins_Pipeline@2@tmp/durable-dcf0766d/script.sh.copy: 1: docker: not found

script returned exit code 127

I tried to modify the script a bit to solve the problem, but none were successful.
Could you please share any idea what the reason for that error message maybe?

4

I suppose that’s because my solution was using the infamous Docker in Docker… And you don’t have Docker in your Docker container (which is a good thing, don’t get me wrong).

5

Not at all, I get it. I will rebuild the Docker image containing Docker and try the solution.