These are my ongoing notes on how to get Jenkins up and running on a headless Ubuntu 18.04.

• Initial install: make sure you configure LVM to provide a big enough volume for what Jenkins needs in the root filesystem. By default, the Ubuntu installer will create a volume of only 4GB; if that happens, extend it as needed from the remaining free space.
• OPTIONAL: Get rid of cloud-init; it's installed by default but I see no value in it:

  
      wait until the VM boots
      login
      echo 'datasource_list: [ None ]' | sudo -s tee /etc/cloud/cloud.cfg.d/90_dpkg.cfg
      sudo apt-get purge cloud-init
      sudo rm -rf /etc/cloud/; sudo rm -rf /var/lib/cloud/
      reboot
  

• Reconfigure the timezone to America/Vancouver, since it may be UTC by default:

  sudo dpkg-reconfigure tzdata

• You must

  sudo apt-add-repository universe

  before installing Jenkins, because it requires a package called daemon which is in that repo. Other stuff needs it too.

• sudo apt-get install ntp

• Install subversion. Although Jenkins has its Java implementation, some of our jobs use the command line app to get info.
• You must install Java 8 (openjdk-8-jdk), which is in the universe repo.
• Install jing. This will probably install a newer Java and make it the default, so

  sudo update-alternatives --config java

  , and set it back to 8.
• Install ant, ant-contrib, and libxml2-utils.
• Install linkchecker.
• Jenkins setup requires that you configure a relative path to the files. If you're runing a vm and proxying the port to your own machine, beware: don't choose the selected port on which you're viewing Jenkins. Instead, choose the port that you know Jenkins is running on IN THE VM. If you screw this up, you can fix it by editing jenkins.model.JenkinsLocationConfiguration.xml in /var/lib/jenkins.
• Install sendmail so Jenkins can send email.
• When setting up Jenkins, accept the suggested package of general-use plugins.
• In Jenkins, install log parser plugin and the ThinBackup plugin.
• In the Jenkins configuration, set the svn version to 1.7 (matches our revision server).
• In the Jenkins global security settings, choose "Project-based Matrix Authorization Strategy" and allow anonymous users to read the appropriate stuff.
• Once Jenkins set up and running, edit /etc/default/jenkins to add an appropriate value for the CSP policy. For example, for an utterly permissive policy, do this:

  JAVA_ARGS="$JAVA_ARGS -Dhudson.model.DirectoryBrowserSupport.CSP=\"\""

  to set the CSP allowing HTML to work properly. Consult docs on CSP to decide exactly what you need.
• As the jenkins user, create a directory /var/lib/jenkins/backups, then use that in the configuration of the ThinBackup plugin. I use this for the full backup schedule: H 12 * * 6 and this for the differential: H 12 * * 1-5
• For Mariage only: install imagemagick and libvips-tools.
• We usually use a configuration where the job workspaces are inside the job folder itself. To make this work, edit jenkins/config.xml, comment out the workspaceDir line, and replace it:

  <!--<workspaceDir>${JENKINS_HOME}/workspace/${ITEM_FULL_NAME}</workspaceDir>-->
    <workspaceDir>${ITEM_ROOTDIR}/workspace</workspaceDir>
  
  

• For Moses project only:

  sudo apt install python3 python3-pip python3-lxml

  sudo -H pip3 install dicttoxml nltk numpy plotly jupyter

  Then install nltk punkt data:

  sudo python3

  import nltk

  nltk.download('punkt')

• Make sure that the folder nltk_data ended up in /usr/share. If it didn't, copy it there. It seems to end up in the wrong place often.