Permission denied with Docker in Docker in Atlassian Bamboo Server - docker

Question

I'm trying to build a docker image using DIND with Atlassian Bamboo.
I've created the deployment/ StatefulSet as follows:
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
labels:
app: bamboo
name: bamboo
namespace: csf
spec:
replicas: 1
serviceName: bamboo
revisionHistoryLimit: 10
selector:
matchLabels:
app: bamboo
template:
metadata:
creationTimestamp: null
labels:
app: bamboo
spec:
containers:
- image: atlassian/bamboo-server:latest
imagePullPolicy: IfNotPresent
name: bamboo-server
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
securityContext:
privileged: true
volumeMounts:
- name: bamboo-home
mountPath: /var/atlassian/application-data/bamboo
- mountPath: /opt/atlassian/bamboo/conf/server.xml
name: bamboo-server-xml
subPath: bamboo-server.xml
- mountPath: /var/run
name: docker-sock
volumes:
- name: bamboo-home
persistentVolumeClaim:
claimName: bamboo-home
- configMap:
defaultMode: 511
name: bamboo-server-xml
name: bamboo-server-xml
- name: docker-sock
hostPath:
path: /var/run
dnsPolicy: ClusterFirst
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
terminationGracePeriodSeconds: 30
Note that I've set privileged: true in securityContext to enable this.
However, when trying to run docker images, I get a permission error:
Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post http://%2Fvar%2Frun%2Fdocker.sock/v1.40/containers/create: dial unix /var/run/docker.sock: connect: permission denied.
See '/var/atlassian/application-data/bamboo/appexecs/docker run --help'
Am I missing something wrt setting up DIND?

Answer 1

The /var/run/docker.sock file on the host system is owned by a different user than the user that is running the bamboo-server container process.
Without knowing any details about your cluster, I would assume docker runs as 'root' (UID=0). The bamboo-server runs as 'bamboo', as can be seen from its Dockerfile, which will normally map to a UID in the 1XXX range on the host system. As these users are different and the container process did not receive any specific permissions over the (host) socket, the error is given.
So I think there are two approaches possible:
Or the container process continues to run as the 'bamboo' user, but is given sufficient permissions on the host system to access /var/run/docker.sock. This would normally mean adding the UID the bamboo user maps to on the host system to the docker group on the host system. However, making changes to the host system might or might not be an option depending on the context of your cluster, and is tricky in a cluster context because the pod could migrate to a different node where the changes were not applied and/or the UID changes.
Or the container is changed as to run as a sufficiently privileged user to begin with, being the root user. There are two ways to accomplish this: 1. you extend and customize the Atlassian provided base image to change the user or 2. you override the user the container runs as at run-time by means of the 'runAsUser' and 'runAsGroup' securityContext instructions as specified here. Both should be '0'.

Answer 2

As mentioned in the documentation here
If you want to run docker as non-root user then you need to add it to the docker group.
Create the docker group if it does not exist
$ sudo groupadd docker
Add your user to the docker group.
$ sudo usermod -aG docker $USER
Log out and log back in so that your group membership is re-evaluated.
$ newgrp docker
Verify that you can run docker commands without sudo
$ docker run hello-world
If that doesn't help you can change the permissions of docker socket to be able to connect to the docker daemon /var/run/docker.sock.
sudo chmod 666 /var/run

Answer 3

A better way to handle this is to run a sidecar container - docker:dind, and export DOCKER_HOST=tcp://dind:2375 in the main Bamboo container. This way you will invoke Docker in a dind container and won't need to mount /var/run/docker.sock