Add predefined Jenkins jobs to Jenkins master in docker - docker

Question

I have now searched the Internet for 2 whole days without any progress. There might be so, that the answer is just a click away, but I cannot find it. I'm blinded. I work on Windows 10 by the way...
The problem is that I want to create a simple Dockerfile, that can create a Docker image with a Jenkins master with everything I want it to contain. For instance:
general Jenkins configuration
users
plugins
jobs
slaves
etc...
Now I at least some parts working... I'm able to get rid of the initial "hello welcome to jenkins"-thing, and define my first user + install plugins that i wrote down in a text file.
BUT when it comes to the freakin jenkins jobs it seems to get a bit more complicated.
Since my Dockerfile takes a "base image" from jenkins/jenkins:lts-alpine, it creates a volume for /var/jenkins_home/ which seems to be where the jobs are stored at. And it seems to be a bit problematic to copy files to this folder. I tried add a COPY instruction in my Dockerfile to copy folder & files that are created when I manually create a job in Jenkins, but it seems like Jenkins does not read them for some reason, even after restarting/reloading from disk. The thing is, it is actually working when copying the jobs after "installation". Like docker cp jobs-on-my-machine container:/var/jenkins_home/jobs, but I dont want a lot of extra stuff outside my Dockerfile. I want to keep it as simple as possible. With this solution I will most likely not even be able to commit this change since the docker diff show this output:
C:\Dev>docker diff 3
C /tmp
A /tmp/hsperfdata_jenkins
A /tmp/hsperfdata_jenkins/6
A /tmp/jetty-0.0.0.0-8080-war-_-any-6459623464825334329.dir
A /tmp/jna--1712433994
A /tmp/winstone4948624124562796293.jar
you see... Nothing have changed in /var/jenkins_home/jobs/ directory... Nothing trackable at all :(
Take a look at my Dockerfile content below:
# Pull the latest Jenkins docker image from Docker Hub.
# Currently Alpine is used because the Internet says its safer :)
from jenkins/jenkins:lts-alpine
# Disable Jenkins setup wizard normally showing up during initial startup
ENV JAVA_OPTS="-Djenkins.install.runSetupWizard=false"
# Copy the groovy script creating the first user into the
# run-on-startup-directory into the docker image
COPY **security.groovy** /usr/share/jenkins/ref/init.groovy.d/security.groovy
# Copy the plugins text file into the docker image
COPY plugins.txt /usr/share/jenkins/ref/plugins.txt
# Run the Jenkins default install-plugins script to install
# plugins defined in the plugins text file
RUN /usr/local/bin/install-plugins.sh < /usr/share/jenkins/ref/plugins.txt
# Add the predefined Jenkins jobs _inside_ folder 'jenkins-jobs' into Jenkins
COPY jenkins-jobs /var/jenkins_home/jobs/
security.groovy content:
#!groovy
import jenkins.model.*
import hudson.security.*
import jenkins.security.s2m.AdminWhitelistRule
def instance = Jenkins.getInstance()
def hudsonRealm = new HudsonPrivateSecurityRealm(false)
hudsonRealm.createAccount("admin", "admin")
instance.setSecurityRealm(hudsonRealm)
def strategy = new FullControlOnceLoggedInAuthorizationStrategy()
instance.setAuthorizationStrategy(strategy)
instance.save()
Jenkins.instance.getInjector().getInstance(AdminWhitelistRule.class).setMasterKillSwitch(false)
plugins.txt:
cloudbees-folder
bouncycastle-api
structs
script-security
workflow-step-api
scm-api
workflow-api
junit
antisamy-markup-formatter
workflow-support
workflow-job
token-macro
build-timeout
credentials
ssh-credentials
plain-credentials
credentials-binding
timestamper
durable-task
workflow-durable-task-step
matrix-project
resource-disposer
ws-cleanup
ant
gradle
pipeline-milestone-step
jquery-detached
jackson2-api
ace-editor
workflow-scm-step
workflow-cps
pipeline-input-step
pipeline-stage-step
pipeline-graph-analysis
pipeline-rest-api
handlebars
momentjs
pipeline-stage-view
pipeline-build-step
pipeline-model-api
pipeline-model-extensions
apache-httpcomponents-client-4-api
jsch
git-client
git-server
workflow-cps-global-lib
display-url-api
mailer
branch-api
workflow-multibranch
authentication-tokens
docker-commons
docker-workflow
pipeline-stage-tags-metadata
pipeline-model-declarative-agent
workflow-basic-steps
pipeline-model-definition
workflow-aggregator
github-api
git
github
github-branch-source
pipeline-github-lib
mapdb-api
subversion
ssh-slaves
matrix-auth
pam-auth
ldap
email-ext
mercurial

Answer 1

In case someone else find this question:
From the GitHub - jenkinsci/docker:
In such a derived image, you can customize your jenkins instance with hook scripts or additional plugins. For this purpose, use /usr/share/jenkins/ref as a place to define the default JENKINS_HOME content you wish the target installation to look like :
When jenkins container starts, it will check JENKINS_HOME has this reference content, and copy them there if required. It will not override such files, so if you upgraded some plugins from UI they won't be reverted on next start.
In case you do want to override, append '.override' to the name of the reference file. E.g. a file named /usr/share/jenkins/ref/config.xml.override will overwrite an existing config.xml file in JENKINS_HOME.
What I've done myself and the thing that is working for me is: copy the jobs directory found on your Jenkins instance to where you are able to run docker build. Place the jobs directory from the Jenkins instance in to another directory e.g jobs_jenkins. Meaning your will have $PWD/jobs_jenkins/jobs
Add the following line in your Dockerfile:
...
FROM jenkins/jenkins:lts-alpine
COPY jobs_jenkins /usr/share/jenkins/ref/
...
From my understanding I think the jenkins image itself run a "startup-script" utilizing /usr/share/jenkins/ref, and the stuff copied directly to /var/jenkins_home will not be present...
For more information read the README.md. (From the GitHub - jenkinsci/docker)