Docker Pipeline plugin in Jenkins - Step-by-Step Execution

Process Flow - Docker Pipeline plugin

Start Jenkins Pipeline

↓

Define Docker Image

↓

Pull or Build Image

↓

Run Container with Commands

↓

Capture Output / Status

↓

Use Container for Build/Test

↓

Stop and Remove Container

↓

End Pipeline

This flow shows how Jenkins uses the Docker Pipeline plugin to define, run, and manage Docker containers during a pipeline build.

Execution Sample

Jenkins

pipeline {
  agent any
  stages {
    stage('Run Docker') {
      steps {
        script {
          docker.image('alpine').inside {
            sh 'echo Hello from Docker'
          }
        }
      }
    }
  }
}

This Jenkins pipeline runs a simple command inside an Alpine Docker container using the Docker Pipeline plugin.

Process Table

Step	Action	Evaluation	Result
1	Start pipeline	N/A	Pipeline started on any agent
2	Define Docker image 'alpine'	docker.image('alpine')	Docker image object created
3	Run container with .inside block	docker.image('alpine').inside { ... }	Container started, shell inside container
4	Execute shell command	sh 'echo Hello from Docker'	Output: Hello from Docker
5	Exit container block	Container stops and cleans up	Container stopped and removed
6	Pipeline stage complete	Stage 'Run Docker' finished	Success
7	Pipeline ends	All stages complete	Pipeline success

💡 Pipeline ends after all stages complete successfully

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 5	Final
dockerImage	undefined	alpine image object	container running	container stopped	container removed

Key Moments - 3 Insights

Why does the container stop after the .inside block ends?

The .inside method runs commands inside a temporary container. When the block finishes, Jenkins automatically stops and removes the container to keep the environment clean, as shown in execution_table step 5.

What happens if the Docker image 'alpine' is not present locally?

Jenkins will pull the 'alpine' image from Docker Hub before running the container, as implied in step 3 where the container starts successfully.

Can we run multiple commands inside the .inside block?

Yes, you can run multiple shell commands inside the .inside block. Each command runs inside the same container session until the block ends.

Visual Quiz - 3 Questions

Look at the execution table, what is the output of the shell command at step 4?

A Hello from Docker

B Container started

C Pipeline success

D Docker image created

💡 Hint

Check the 'Result' column in row for step 4 in the execution_table.

At which step does the container stop and get removed?

A Step 3

B Step 5

C Step 6

D Step 7

💡 Hint

Look for the step describing container stop and cleanup in the execution_table.

If the Docker image 'alpine' was missing locally, what would change in the execution flow?

A Container would run without image

B Pipeline would fail immediately

C Jenkins would pull the image before running container

D Pipeline would skip the Docker stage

💡 Hint

Refer to key_moments explanation about image presence and pulling.

Concept Snapshot

Docker Pipeline plugin lets Jenkins run commands inside Docker containers.
Use docker.image('name').inside { ... } to run commands inside a container.
Jenkins pulls the image if missing, starts container, runs commands, then stops and removes container.
This keeps builds clean and isolated.
Use inside block for temporary container sessions.

Full Transcript

This visual execution trace shows how Jenkins uses the Docker Pipeline plugin to run commands inside Docker containers during a pipeline. The pipeline starts, defines a Docker image 'alpine', and runs a container with the .inside method. Inside the container, it executes a shell command that prints 'Hello from Docker'. After the commands finish, Jenkins stops and removes the container automatically. The pipeline then completes successfully. Variables like the dockerImage track the container state from creation to removal. Key moments clarify why containers stop after the block and how Jenkins pulls images if missing. The visual quiz tests understanding of output, container lifecycle, and image pulling behavior. The snapshot summarizes the plugin usage for quick reference.