Container Jenkins cannot find Docker command

Question

in short, I’m trying to run one container inside another. Where the first container to go up is based on a Jenkins image and the second on a gcc image (which is only for testing).

this is the step by step of what I did:

1. I raised a Jenkins container based on the image jenkins\jenkins with the following command:

   • docker run -it -p 1234:8080 -v jenkins_home:/var/jenkins_home -u 0 jenkins/jenkins

   • jenkins_home is a volume created with the command docker volume create jenkins_home

2. I installed the plugins Docker, Docker Slaves and Docker Pipeline.

3. I created a job pipeline:

   pipeline {
       stages {        
           stage('Container') {
               agent {
                   docker {
                       image 'gcc'
                       args '-v ${nomedocurso}:/curso/'
                   }
               }
               steps {
                   sh 'ls -l'
               }
           }
       }
   }
   

   • In that step, Jnenkins was not finding Docker:

     + Docker Inspect -f . gcc /var/jenkins_home/Workspace/curso-c@2@tmp/Durable-ee333f1e/script.sh: 1: /var/jenkins_home/Workspace/curso-c@2@tmp/Durable-ee333f1e/script.sh: Docker: not found

4. I tried to include the label parameter:

   pipeline {
       agent {
           label 'docker' 
       }
       stages {        
           stage('Container') {
               agent {
                   docker {
                       label 'docker'
                       image 'gcc'
                       args '-v ${nomedocurso}:/curso/'
                   }
               }
               steps {
                   sh 'ls -l'
               }
           }
       }
   }
   

   • But Jenkins kept complaining:

     Still Waiting to Schedule task
     pra Jenkins' doesn’t have label ːDocker'

---

• Because Docker’s not being found by Jenkins?
• How to set up and run a Docker pipeline in one of the stages?

Answer 1

You shouldn’t start a container inside another container. Although not impossible, it simply should not be done and "hurts" the purpose of containers.

This article (in English) talks a little about this and presents an alternative. It seems to me that it is for a scenario similar to yours: https://itnext.io/docker-in-docker-521958d34efd

There is also a project that allows you to do this in a simpler way, but it depends on the images being available in the project: https://www.testcontainers.org/