Run docker inside Jenkins

how-to-docker-jenkins.md

Create a Dockerfile with the following contents

FROM jenkins:2.32.3

USER root
RUN apt-get -qq update \
   && apt-get -qq -y install \
   curl

RUN curl -sSL https://get.docker.com/ | sh

RUN usermod -a -G staff jenkins

USER jenkins

Create an image:

docker build -t jenkins_docker .

Run the container:

docker run -d -p 8080:8080 -p 4040:4040 -v /var/run/docker.sock:/var/run/docker.sock jenkins_docker

Demo: https://drive.google.com/file/d/0Bz8VjLQTuhwvT05wMlFrYnJwZVE/view?usp=sharing

This code does not work.
Docker version: 17.12.1-ce
Error:
Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get http://%2Fvar%2Frun%2Fdocker.sock/v1.37/version: dial unix /var/run/docker.sock: connect: permission denied
This work only when USER root, not USER jenkins.
Any ideas?

Ok it is working now. Docker group id must be the same on host and container machine.
Helpful commands:
get group id:
getent group docker
set group id:
groupmod -g 3000 docker