How can I add software or other packages to a docker container?

You will need to install all your dependencies at docker container build time.

You can make your own Dockerfile off of the jenkins library, and then put custom stuff in there. Your Dockerfile can look like

FROM jenkins:latestMAINTAINER BecksRUN apt-get update && apt-get install -y {space delimited list of package}

Then, you can do something like...

docker build -t jenkins-docker --file Dockerfile .docker run -it -d --name=jenkins-docker jenkins-docker

I might not have written all the syntax correctly, but this is basically what you need to do. If you want the run step to spin up jenkins, follow along with what they are doing in the existing Dockerfile here and add relevant sections to your dockerfile, to add some RUN steps to run jenkins.

Came across this page, which approaches a similar problem, although it also mounts the docker sock inside another container, to kind of connect one container to another. Given that its an external link, here's the relevant dockerfile from there,

FROM jenkins:1.596USER rootRUN apt-get update \      && apt-get install -y sudo \      && rm -rf /var/lib/apt/lists/*RUN echo "jenkins ALL=NOPASSWD: ALL" >> /etc/sudoersUSER jenkinsCOPY plugins.txt /usr/share/jenkins/plugins.txtRUN /usr/local/bin/plugins.sh /usr/share/jenkins/plugins.txt

And this is how you can spin it up.

docker build -t myjenk ....Successfully built 471fc0d22bff$ docker run -d -v /var/run/docker.sock:/var/run/docker.sock \                -v $(which docker):/usr/bin/docker -p 8080:8080 myjenk

I strongly suggest going through that post. Its pretty awesome.