Daniel Beck Yeah, In Ubuntu 14.04 you need a custom repo to install openjdk 8... To make things more interesting given that the "recommended" version of java in Ubuntu is 8 you can end with it installed when you install Java 9 in Ubuntu 16.04 so even strictly requirements on Java 8 may not be enough to guarantee nothing.
So, I would recommend to follow the same logic than the RPM package, java dependency was dropped for similar issues but the startup script includes a facility to check for a valid java version. I have a first draft of a java 8 detection function (need to test on debian not only on ubuntu) that I can incorporate to the debian init script. This way
- We make easy to install the package without forcing anyone to a concrete java configuration
- We do not really should care about how java is installed as long as we can use it, I, for example, like to install it manually via tar.gz files and after that use update-alternatives, every time a package installs automatically openjdk packages or similar I have to redo my entire conf
- We make sure the jenkins instance is only run with an appropriate java version
- We can provide a meaningful error message if an invalid java version is used to run jenkins