Jenkinsfile Throws docker: not found in Jenkins Running on Docker for CI/CD of Spring Boot Project

I'm encountering an issue in my Jenkins CI/CD pipeline where Jenkins running in a Docker container is unable to find the docker command during the build process. Below is the setup:

• Groovy Script for creating a Jenkins pipeline job programmatically.
• Jenkins Dockerfile that installs Docker CLI. Docker Compose to define
• services, including Jenkins and its dependencies. Jenkinsfile which
• uses Docker to build a Docker image for the project.

Note : As I work with Windows , I change /var/run/docker.sock:/var/run/docker.sock to /var/run/docker.sock.raw:/var/run/docker.sock to detect testcontainer in the pipeline. Otherwise I cannot run integration.

Here is the groovy file shown below

import hudson.plugins.git.UserRemoteConfig
import hudson.plugins.git.BranchSpec
import hudson.plugins.git.GitSCM
import jenkins.model.*
import org.jenkinsci.plugins.workflow.cps.CpsScmFlowDefinition

def instance = Jenkins.getInstance()

def jobName = "flightsearchapi"
def job = instance.getItem(jobName)

if (job != null) {
    job.delete()
}

def pipelineJob = instance.createProject(org.jenkinsci.plugins.workflow.job.WorkflowJob, jobName)
def definition = new CpsScmFlowDefinition(
        new GitSCM(
                [
                        new UserRemoteConfig("https://github.com/Rapter1990/flightsearchapi.git", null, null, null)
                ],
                [new BranchSpec("*/development/issue-2/implement-jenkins-for-ci-cd")],
                false, Collections.emptyList(),
                null, null, Collections.emptyList()
        ),
        "Jenkinsfile"
)
definition.setLightweight(true)
pipelineJob.setDefinition(definition)
pipelineJob.save()

println("Pipeline job '${jobName}' has been successfully created!")

Here is the plugin.txt

workflow-aggregator
git
job-dsl
ws-cleanup
docker-plugin
docker-workflow
docker-commons

Here is the Dockerfile shown below

FROM jenkins/jenkins:lts

# Plugin list
COPY plugins.txt /usr/share/jenkins/ref/plugins.txt
RUN jenkins-plugin-cli --plugin-file /usr/share/jenkins/ref/plugins.txt

# For Groovy scripts, init.d directory
COPY init.groovy.d/ /var/jenkins_home/init.groovy.d/

# Install Docker CLI
USER root
RUN apt-get update && apt-get install -y docker.io

Here is the docker-compose.yml

version: '3.9'

services:
  jenkins:
    build:
      context: .
      dockerfile: Dockerfile
    container_name: jenkins-server
    ports:
      - "8080:8080"    # Expose Jenkins UI on port 8080
      - "50000:50000"  # Expose port for Jenkins agents
    volumes:
      - jenkins_home:/var/jenkins_home   # Persistent Jenkins data
      - /var/run/docker.sock.raw:/var/run/docker.sock # Mount Docker socket for Docker builds
      - ../k8s:/var/jenkins_home/k8s # Mount Kubernetes configuration files (optional)
      - ./init.groovy.d:/var/jenkins_home/init.groovy.d # Mount Jenkins init scripts (optional)
    environment:
      JAVA_OPTS: "-Djenkins.install.runSetupWizard=false" # Skip setup wizard (optional)
    user: root # Run as root to allow installing dependencies

volumes:
  jenkins_home:

Here is the Jenkinsfile shown below

pipeline {
    agent {
        docker {
            image 'maven:3.9.9-amazoncorretto-21-alpine'
            args '-v /root/.m2:/root/.m2'
        }
    }

    environment {
        GIT_REPO_URL = 'https://github.com/Rapter1990/flightsearchapi.git'
        BRANCH_NAME = 'development/issue-2/implement-jenkins-for-ci-cd'
        DOCKERHUB_USERNAME = 'noyandocker'
        DOCKER_IMAGE_NAME = 'flightsearchapi-jenkins'
    }

    stages {
        stage('Checkout') {
            steps {
                script {
                    checkout([
                        $class: 'GitSCM',
                        branches: [[name: "*/${env.BRANCH_NAME}"]],
                        userRemoteConfigs: [[url: "${env.GIT_REPO_URL}"]]
                    ])
                }
            }
        }

        stage('Build') {
            steps {
                sh 'mvn clean install'
            }
        }

        stage('Build Docker Image') {
            steps {
                sh "docker build -t ${env.DOCKERHUB_USERNAME}/${env.DOCKER_IMAGE_NAME}:latest ."
            }
        }

        stage('Push Docker Image') {
            steps {
                withDockerRegistry([credentialsId: 'docker-hub-credentials', url: '']) {
                    sh "docker push ${env.DOCKERHUB_USERNAME}/${env.DOCKER_IMAGE_NAME}:latest"
                }
            }
        }

    }

    post {
            always {
                cleanWs(cleanWhenNotBuilt: false,
                        deleteDirs: true,
                        disableDeferredWipeout: true,
                        notFailBuild: true,
                        patterns: [[pattern: '.gitignore', type: 'INCLUDE'],
                                   [pattern: '.propsfile', type: 'EXCLUDE']])
            }
        }
}

In the pipeline, I am attempting to build and push a Docker image as part of the CI/CD process, but the error message shows

+ docker build -t noyandocker/flightsearchapi-jenkins:latest .
/var/jenkins_home/workspace/flightsearchapi@tmp/durable-7294ca4e/script.sh.copy: line 1: docker: not found

Can you fix the issue ?

The issue disappeared after I followed these steps shown below

1 ) Change agent as any from docker image

2 ) Define mvn for build step and docker for its relevant step

Here is the code shown below.

pipeline {
    agent any
    ...

    stage('Build') {
                agent {
                        docker {
                            image 'maven:3.9.9-amazoncorretto-21-alpine'
                        }
                    }
                steps {
                    sh 'mvn clean install'
                }
            }
    
            stage('Build Docker Image') {
                agent {
                    docker {
                        image 'docker:27.5.1'
                    }
                }
                steps {
                    sh "docker build -t ${env.DOCKERHUB_USERNAME}/${env.DOCKER_IMAGE_NAME}:latest ."
                }
            }
    
            stage('Push Docker Image') {
                agent {
                    docker {
                        image 'docker:27.5.1'
                    }
                }
                steps {
                    withDockerRegistry([credentialsId: 'docker-hub-credentials', url: '']) {
                        sh "docker push ${env.DOCKERHUB_USERNAME}/${env.DOCKER_IMAGE_NAME}:latest"
                    }
                }
            }
    ...
}