Add user in Docker container, UID mismatch when running Jenkins job - docker

Question

I am running a Jenkins pipeline in a Docker container. The Docker container creates an unpriviliged user to run as:
RUN useradd jenkins --shell /bin/bash --create-home
RUN mkdir -p /home/jenkins/src && chown -R jenkins:jenkins /home/jenkins
USER jenkins
WORKDIR /home/jenkins/src
Jenkins runs this as:
docker run -t -d -u 1000:1000 [-v and -e flags etc.]
This works when I run Jenkins manually as my personal account (uid 1000) on the host. But now I changed it so that Jenkins is started automatically by systemd, and using a specifiy jenkins user with uid 1006, gid 1009:
docker run -t -d -u 1006:1009 [-v and -e flags etc.]
This mismatch causes my build to fail. I also get all kinds of problems, like this prompt in the container:
I have no name!#6d3b27a803e4:/$
Creating a jenkins user in the container seems like something that there should be a recipe for. How do I get the UIDs on host and container to match? What is the best practice?
Add something like usermod --uid $HOST_UID jenkins to the Dockerfile?
There seems to be no way to tell Docker to map host uid 1006 to container uid 1000, is there?

Answer 1

I face the same problem when run Jenkins job and found the solution working for me.
As you wrote above if you run job in container Jenkins automatically starts Docker like this:
docker run -t -d -u 113:117 [-v and -e flags etc.]
He takes his UID and GID locally and uses in Docker run command. But when steps commands start executing in the container docker doesn't have this values inside. It's cause of this trouble:
I have no name!#6d3b27a803e4:/$
The solution for me was to mount "passwd" and "group" files inside container like this:
pipeline {
agent {
docker {
image 'your_image'
args '-v /etc/passwd:/etc/passwd -v /etc/group:/etc/group'
}
}
stages {
stage('stage_name') {
steps {
sh '''
some_commands
'''
}
}
}
And create user in Dockerfile like this:
RUN groupadd jenkins && useradd -m -d /var/lib/jenkins -g jenkins -G root jenkins
Hope this helps someone)

Answer 2

This worked for me:
docker {
image 'your_image'
args '-e HOME=/tmp/home'
}
/tmp is writable for everyone. No need to create user.