I'm on Ubuntu 12.04 and I need to install a version of Jenkins greater than the one provided in the Ubuntu repositories (1.424.6). Specifically I at least need version 1.426 (I want to use API tokens for an external script), but I would like to have the newest LTS version, 1.480.1.
I can install version 1.424.6 just fine through the default, Canonical repositories, but when I try to install Jenkins from their instructions, I get no upstart script as expected.
How can I install and set up a newer version of Jenkins on Ubuntu 12.04?