How to mount docker volume with jenkins docker container?

Question

I have jenkins running inside container and project source code on github.

I need to run project in container on the same host as jenkins, but not as docker-in-docker, i want to run them as sibling containers.

My pipeline looks like this:

1. pull the source from github
2. build the project image
3. run the project container

What i do right now is using the docker socket of host from jenkins container:

/var/run/docker.sock:/var/run/docker.sock

I have problem when jenkins container mount the volume with source code from /var/jenkins_home/workspace/BRANCH_NAME to project container:

volumes:
 - ./servers/identity/app:/srv/app

i am getting empty folder "/srv/app" in project container

My best guess is that docker tries to mount it from host and not from the jenkins container.

So the question is: how can i explicitly set the container from which i mount the volume?

Answer 1

I got the same issue when using Jenkins docker container to run another container.

Senario 1 - Running container inside Jenkins docker container

This is not a recommended way, explanations goes here. If you still need to use this approach, then this problem is not a problem.

Senario 2 - Running docker client inside Jenkins container

Suppose, we need to run another container (ContainerA) inside Jenkins docker container, docker pipeline plugin will use --volumes-from to mount Jenkins container volume to ContainerA.

If you trying to use --volume or -v to map specific directory in Jenkins container to ContainerA, you will got an unexpected behavior.

That's because --volumes or -v would try to map directories in host to ContainerA, rather than mapping from directories inside Jenkins container. If the directories not found in host, then you will get an empty dir inside ContainerA.

In short, we can not map a specific directory from containerA to containerB, we could only mount the whole volumes from containerA to containerB, and volume alias is not supported.

Solution

1. If your Jenkins is running with host volume, you can map the host directories to the target container.
2. Otherwise, you can access the files inside the newly created container with the same location as Jenkins container.

Answer 2

try:

docker run -d --volumes-from <ContainerID> <YourImage>

where container ID is id of container you want for mont data from.

You can also create volume, by:

docker volume create <volname>

and assign it to both containers

volumes:
 - <volname>:/srv/app

Answer 3

Sharing the sock between the Host and Jenkins was my problem because "/var/jenkins_home" is most likely a volume for the Jenkins container.

My solution was installing docker inside a systemd container without sharing the sock.

docker run -d --name jenkins \
    --restart=unless-stopped \
    --privileged \
    -v /sys/fs/cgroup:/sys/fs/cgroup:ro \
    -v jenkins-vol:/var/lib/jenkins \
    --tmpfs /run \
    --tmpfs /run/lock \
    ubuntu:16.04 /sbin/init

Then install Jenkins, Docker and Docker Compose on it.