Hi,
Even before joining the WMF I have heard about the "opportunities for sysadmins to contribute", the possibility to get involved in Wikipedia that way, how great https://labs.wikimedia.org/ is for this purpose and the inevitable mention to Puppet at some point.
While improving http://www.mediawiki.org/wiki/How_to_contribute I couldn't find (m)any details about how a volunteer sysadmin could enter this path and make progress until, say, becoming a Wikimedia sysadmin wearing a 'got [Wikimedia logo] root' shirt.
http://www.mediawiki.org/wiki/Sysadmin_hub seems to be the closest landing page for a sysadmin volunteer, but that page needs love and there is little to be found there for wannabe contributors.
I can put some time sorting out this, but I need help from the people in the know. We could start defining the first step that a potential sysadmin volunteer could make in order to become a helpful contributor.