How to mount volume in a docker job inside a dockerized jenkins

[Nicolas Geraud]

Hi all,

i'm using a dockerized jenkins (from jenkinsci/jenkins:2.2) and mounting the following volumes from my host :
volumes:
        - "/opt/jenkins:/var/jenkins_home"
        - "/var/run/docker.sock:/var/run/docker.sock"


I've created a job that launch a docker container to build some python files :
--Dockerfile

FROM python:3-onbuild
CMD [ "python" ]

docker command of my jenkins job :
$docker run --rm -v `pwd`:"/usr/src/myapp" graviteeio/python3 python src/main/python/package_bundles.py

But the result is :

Starting docker_package_bundle_and_publish_1
Attaching to docker_package_bundle_and_publish_1
[36mpackage_bundle_and_publish_1 | [0m python: can't open file './src/main/python/package_bundles.py': [Errno 2] No such file or directory
[36mdocker_package_bundle_and_publish_1 exited with code 2
[0mFinished: SUCCESS

This is working fine on a classic jenkins, but not on a dockerized jenkins. I've googled this error and it seems that mounting a volume inside a container with an already mounting volume doesn't work.

I think that some of you have already test the same use case so, how to do that ?

Thanks for any clue.
I need to test a data volume instead of mounting a host volume.

[nicolas de loof]

For this to work, you'll need the host path to be the exact same as the jenkins container path, i.e. not use /opt/jenkins but /var/jenkins_home on host

so `pwd` will resolve to some /var/jenkins_home/... subfolder that make sense to be mounted from host into your side container

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[Nicolas Geraud]

Thanks for the quick answer, I'll test this tonight.

Do you have any blog post (or perhaps i've missed a "Quoi de neuf Docker" episode) which explain why it works like this ?

[nicolas de loof]

The reason it works like this is the bind mount is done from host, so need a valid fully qualified host path, but the `pwd` command is ran inside jenkins container, so resolves to container filesystem.

A possible alternate approach is for you to rely on " --volumes-from $(hostname) ", as a container hostname defaults to it's ID. As a result, your second container will share /var/jenkins_home with jenkins master. Then you can run some commands using $workspace as a valid path in both containers :

docker run --rm --volumes-from $(hostname) graviteeio/python3 python ${WORKSPACE}/package_bundles.py

To view this discussion on the web visit https://groups.google.com/d/msgid/jenkinsci-users/f8487560-3e1a-44a2-883f-b5ae02213cc1%40googlegroups.com.

[Nicolas Geraud]

Ok, with some tests I know understand how "sibling containers" work.

thanks for your help