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By default, all containers within a Kubernetes Pod share the same filesystem. In this tutorial, we’ll demonstrate how to create a file in an Ubuntu container and then read it from a Node.js container within the same Pod using a Jenkins pipeline.
Containers in the same Pod share volumes and file systems, allowing seamless data exchange without additional configuration.

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Jenkins Pipeline Configuration

Paste the following pipeline definition into your Jenkinsfile to set up two containers—ubuntu-container and node-container—in a single Pod: 
pipeline {
  agent {
    kubernetes {
      yaml """
apiVersion: v1
kind: Pod
spec:
  containers:
  - name: ubuntu-container
    image: ubuntu
    command: ['sleep']
    args: ['infinity']
  - name: node-container
    image: node:18-alpine
    command: ['cat']
    tty: true
"""
      defaultContainer 'ubuntu-container'
    }
  }

  stages {
    stage('Create File on Ubuntu') {
      steps {
        sh '''
          # Display the hostname
          hostname

          # Write data to a file
          echo important_UBUNTU_data > ubuntu-$BUILD_ID.txt

          # Confirm the file was created
          ls -ltr ubuntu-$BUILD_ID.txt
        '''
      }
    }

    stage('Access File on Node') {
      steps {
        container('node-container') {
          sh '''
            # Verify Node.js and npm versions
            node -v
            npm -v

            # List and read the file created earlier
            ls -ltr ubuntu-$BUILD_ID.txt
            cat ubuntu-$BUILD_ID.txt
          '''
        }
      }
    }
  }
}

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Pipeline in Action

Once you commit and run this pipeline, Jenkins will create the Pod and execute both stages. The Ubuntu container writes ubuntu-$BUILD_ID.txt, and the Node.js container reads it immediately afterward.
The image shows a Jenkins dashboard displaying the status of a pipeline named "k8s-cloud-agent-demo," with several stages and their execution results.
According to the Kubernetes Pod Lifecycle documentation, all containers in a Pod can share volumes and files.
The image is a screenshot from the Kubernetes documentation website, showing a diagram of a multi-container Pod with a file puller sidecar, a web server, and a shared volume.

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Console Output Example

Below is an excerpt from the Jenkins console log illustrating how the file is shared between containers: 
[ubuntu-container] Running shell script
+ hostname
k8s-cloud-agent-demo-5-rv7b8-8frt0-n41pw
+ echo important_UBUNTU_data
+ ls -ltr ubuntu-5.txt
-rw-r--r-- 1 root root 22 Nov 10 09:47 ubuntu-5.txt

[node-container] Running shell script
+ node -v
v18.20.4
+ npm -v
8.19.2
+ ls -ltr ubuntu-5.txt
-rw-r--r-- 1 root root 22 Nov 10 09:47 ubuntu-5.txt
+ cat ubuntu-5.txt
important_UBUNTU_data

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Comparing Jenkins Agent Strategies

Choose the right Jenkins agent model based on your infrastructure and maintenance requirements:
Agent TypeDescription
Kubernetes Cloud AgentOn-demand Pods; auto-provisioned and cleaned up per job.
Docker AgentTemporary containers managed by Jenkins; easy to customize.
Static NodeAlways-on VMs or servers; requires manual OS and tool updates.
Static nodes demand ongoing maintenance (OS patches, software upgrades). For most CI/CD workflows, dynamic agents reduce resource waste and simplify updates.

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