Docker in docker within Jenkins on Kubernetes. Eat at Arby's.

Jenkinsfile

pipeline {
  agent {
    kubernetes {
      label 'dind'
      defaultContainer 'docker'
      yaml """
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: jenkins
spec:
  containers:
    - name: docker
      image: docker:latest
      command:
        - /bin/cat
      tty: true
      volumeMounts:
        - name: dind-certs
          mountPath: /certs
      env:
        - name: DOCKER_TLS_CERTDIR
          value: /certs
        - name: DOCKER_CERT_PATH
          value: /certs
        - name: DOCKER_TLS_VERIFY
          value: 1
        - name: DOCKER_HOST
          value: tcp://localhost:2376
    - name: dind
      image: docker:dind
      securityContext:
        privileged: true
      env:
        - name: DOCKER_TLS_CERTDIR
          value: /certs
      volumeMounts:
        - name: dind-storage
          mountPath: /var/lib/docker
        - name: dind-certs
          mountPath: /certs
  volumes:
    - name: dind-storage
      emptyDir: {}
    - name: dind-certs
      emptyDir: {}
"""
    }
  }
  stages {
    stage('Run Docker Things') {
      steps {
        sh 'printenv'
        sh 'docker info'
      }
    }
  }
}

k8s.yaml

---
# The following is just like that above, but will configure a generally available container for all Pipelines using the configuration as code plugin
jenkins:
  clouds:
  - kubernetes:
      connectTimeout: 5
      # These variables must be present in the environment in order for the
      # Jenkins agents to "find" the Jenkins master once they are launched,
      # such that they may bootstrap.
      jenkinsUrl: "http://${JENKINS_SERVICE_HOST}:${JENKINS_SERVICE_PORT}"
      maxRequestsPerHostStr: "32"
      name: "kubernetes"
      readTimeout: 15
      skipTlsVerify: true
      templates:
      # The "docker" container allows for the building and validation of
      # Docker containers on top of the existing kubernetes cluster without
      # requiring the kubernetes cluster to expose access to its docker socket
      - containers:
        - args: "cat"
          command: "/bin/sh -c"
          envVars:
          - envVar:
              key: 'DOCKER_HOST'
              value: 'tcp://localhost:2376'
          - envVar:
              key: "DOCKER_TLS_CERTDIR"
              value: "/certs"
          - envVar:
              key: "DOCKER_CERT_PATH"
              value: "/certs/client"
          - envVar:
              key: "DOCKER_TLS_VERIFY"
              value: "1"
          image: 'docker:stable'
          livenessProbe:
            failureThreshold: 0
            initialDelaySeconds: 0
            periodSeconds: 0
            successThreshold: 0
            timeoutSeconds: 0
          name: "docker"
          ttyEnabled: true
        - alwaysPullImage: true
          envVars:
          - envVar:
              key: "DOCKER_TLS_CERTDIR"
              value: "/certs"
          image: 'docker:dind'
          livenessProbe:
            failureThreshold: 0
            initialDelaySeconds: 0
            periodSeconds: 0
            successThreshold: 0
            timeoutSeconds: 0
          name: 'dind'
          privileged: true
          ttyEnabled: true
        # The jenkins-agent image is required in order to have a Jenkins agent
        # which can access resources like git.lo, etc.
        #
        # It is basically a jenkins agent image with our root certificate
        # bundled into it
        - args: "^${computer.jnlpmac} ^${computer.name}"
          command: ""
          image: "jenkins/jnlp-slave:latest"
          alwaysPullImage: true
          livenessProbe:
            failureThreshold: 0
            initialDelaySeconds: 0
            periodSeconds: 0
            successThreshold: 0
            timeoutSeconds: 0
          # The name "jnlp" is special and required in order to override the
          # built in container which the Kubernetes pod launches.
          name: "jnlp"
          ttyEnabled: true
        label: 'docker'
        name: 'docker'
        volumes:
        - emptyDirVolume:
            memory: false
            mountPath: '/var/lib/docker'
        - emptyDirVolume:
            memory: false
            mountPath: "/certs"
        workspaceVolume:
          emptyDirWorkspaceVolume:
            memory: false

Thanks for sharing. For reference, in the dind image now, you need to modify it to the below content.
Replace mountPath: "/certs" in line 40 with mountPath: "/certs/client".

Thanks for sharing the configuration file, it helps me a lot to !

Replace the deprecated image: image: "jenkins/jnlp-slave:latest" in line 66 with image: "jenkins/inbound-agent:latest" to get it work.