Some notes regarding dist-upgrades from wheezy to jessie with Foreman 1.8 (probably also valid for later versions, but this was not tested). Please note that this kind of upgrade is not officially supported by the Foreman project.
First of all, upgrade everything to the latest version available for wheezy, especially all Foreman related packages. Furthermore it's needed that everything was configured with foreman-installer and no manual changes were made later. This means, a run of foreman-installer before the dist-upgrade should bring in no changes.
- The package ruby-rdoc is not upgradable, so it has to be removed (but not purged), together with all dependent packages (including foreman-installer).
- Now all sources.list entries can be changed to jessie.
- If using the PuppetLabs repository, no jessie release packages are available, you can use puppetlabs-release-testing, but be aware that there are no updates after Puppet 3.8.1 available.
- If using Debian Puppet packages, see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=782325 for a potential source of a (harmless) error.
- While the dist-upgrade manual answering regarding apache modules and disabling of the ssl module is necessary. Just do everything needed for the upgrade to succeed.
- Reboot into the new kernel.
- If using PostgreSQL on the same host as database server, install the 9.4 packages and migrate the database with the help of pg_upgradecluster.
- Now foreman-installer can be installed and invoked again, configuring everything according to the old answers file.
- Everything should work again, on Debian/jessie.