Changing the user's uid in a pre-build docker container (jenkins)
I am new to docker, so if this is a fairly obvious process that I am missing, I do apologize for the dumb question up front.
I am setting up a continuous integration server using the jenkins docker image. I did a docker pull jenkins, and created a user jenkins to allow me to mount the /var/jenkins_home in the container to my host's /var/jenkins_home (also owned by jenkins:jenkins user).
the problem is that the container seems to define the jenkins user with uid 102, but my host has the jenkins user as 1002, so when I run it I get:
docker run --name jenkins -u jenkins -p 8080 -v /var/jenkins_home:/var/jenkins_home jenkins
/usr/local/bin/jenkins.sh: line 25: /var/jenkins_home/copy_reference_file.log: Permission denied
I would simply make the uid for the host's jenkins user be 102 in /etc/passwd, but that uid is already taken by sshd. I think the solution is to change the container to use uid 1002 instead, but I am not sure how.
Edit
Actually, user 102 on the host is messagebus, not sshd.
Answer
Please take a look at the docker file I just uploaded: https://github.com/bdruemen/jenkins-docker-uid-from-volume/blob/master/Dockerfile . Here the UID is extracted from a mounted volume (host directory), with
stat -c '%u' <VOLUME-PATH>
Then the UID of the container user is changed to the same value with
usermod -u <UID>
This has to be done as root, but then root privileges are dropped with
gosu <USERNAME> <COMMAND>
Everything is done in the ENTRYPOINT, so the real UID is unknown until you run
docker run -d -v <HOST-DIRECTORY>:<VOLUME-PATH> ...
Note that after changing the UID, there might be some other files no longer accessible for the process in the container, so you might need a
chown -R <USERNAME> <SOME-PATH>
before the gosu command.
You can also change the GID, see my answer here Jenkins in docker with access to host docker and maybe you want to change both to increase security.