Docker.Image.mountJenkinsUser fails when Build executor runs in a container about ces-build-lib HOT 1 CLOSED

The problem was related to this mount triggered by MavenInDocker (realized by Docker.Image.mountJenkinsUser):

 -v /var/jenkins_home/workspace/ature_3_continuous_delivery-6HRXLXYING3RPQ2T3ATY6DOVMNEXY7ZFTGPCHQBMB7KHPI2V5JBQ/.jenkins/etc/passwd:/etc/passwd:ro

The problem on this specific Jenkins instance was, that the build executor of the Jenkins instance was a docker container that mounted the docker socket so Jenkins Pipelines can start Docker containers on the same docker host as the build executor (i.e. sibling containers).

However, the path /var/lib/jenkins_home on the host was mounted into /var/jenkins_home on the build executor (see jenkinsci/docker/Dockerfile).

So, when the Pipeline (on the build executor) mounted files from the workspace to its sibling container, the docker host could not mount /var/jenkins_home because it did not exist on the host (as the files were positioned under /var/lib/jenkins_home there).

So we learned:
When build executors are Docker containers that allow pipelines to access their docker host,
the JENKINS_HOME in the build executor's container should have the same absolute path as the JENKINS_HOME on the docker host.

Otherwise in Pipelines mounting files from the workspace into docker containers created within the Pipeline will fail.

There are two solutions:

• Change the JENKINS_HOME on the docker host
• Change the JENKINS_HOME in the build executor container.

from ces-build-lib.