Docker mounted volume GID mismatch causes error: dial unix /var/run/docker.sock: connect: permission denied

Question

Using the official jenkins image, I have installed docker and docker-compose and added jenkins to the docker group (GID 999 in the container).

After that, I shared the /var/run/docker.sock of the host so enable jenkins create "siblings" containers. It happens that the original file have GID 134 and with this GID is mounted. I am getting the following error:

demo_1 | docker: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post http://%2Fvar%2Frun%2Fdocker.sock/v1.32/containers/create: dial unix /var/run/docker.sock: connect: permission denied. demo_1 | See 'docker run --help'.

Any idea about how to solve this?

My minimal (and not optimized yet) Dockerfile is:

FROM jenkins/jenkins:lts

USER root

RUN apt-get update && apt-get install -y apt-transport-https \
     ca-certificates \
     curl \
     gnupg2 \
     software-properties-common

RUN curl -fsSL https://download.docker.com/linux/$(. /etc/os-release; echo "$ID")/gpg | apt-key add -
RUN apt-key fingerprint 0EBFCD88
RUN add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/$(. /etc/os-release; echo "$ID") \
   $(lsb_release -cs) \
   stable"

RUN apt-get update
RUN apt-get install -y docker-ce docker-compose
RUN usermod -aG docker jenkins

USER jenkins
RUN newgrp docker

I have also created a docker-compose to test it:

version: '2'
services:
    demo:
        build: .
        ports:
            - 8080:8080
            - 50000:50000
        volumes:
            - /var/run/docker.sock:/var/run/docker.sock
        command: >
            /bin/sh -c "
                set -e
                groups
                docker -v
                docker-compose -v
                ls -ln /var/run/docker.sock
                id jenkins
                docker run hello-world
            "

The output is:

demo_1  | jenkins staff docker
demo_1  | Docker version 17.09.0-ce, build afdb6d4
demo_1  | docker-compose version 1.8.0, build unknown
demo_1  | srw-rw---- 1 0 134 0 Sep 30 07:36 /var/run/docker.sock
demo_1  | uid=1000(jenkins) gid=1000(jenkins) groups=1000(jenkins),50(staff),999(docker)
demo_1  | docker: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post http://%2Fvar%2Frun%2Fdocker.sock/v1.32/containers/create: dial unix /var/run/docker.sock: connect: permission denied.
demo_1  | See 'docker run --help'.

Francisco Canela Francisco Canela · Accepted Answer · 2017-10-08T17:59:49

I gave the problem a dirty fix, so I am letting this question open to see if a better one appears.

As the /var/run/docker.sock file is owned by root, which have the same UID, I added jenkins to the list of sudoers without need to type password:

RUN adduser jenkins sudo
RUN echo "jenkins ALL=NOPASSWD: ALL" >> /etc/sudoers

This solved the issue. I dislike it, but it works.

Docker mounted volume GID mismatch causes error: dial unix /var/run/docker.sock: connect: permission denied

1 Answers