I do agree that "Off Topic" is used frequently where "Not Constructive" may be a better choice (particularly for shopping questions), but I don't think your examples really make the case. Only two of them are strong candidates for "Not Constructive" closes.
You did however bring up what I consider to be a very important point:
If we don't even bother to select the appropriate close reason when VTC'ing, how are the users going to learn?
Close reasons shouldn't be the only instrument of education. When closing a question people should really be leaving comments explaining what's wrong, and how it could be corrected.
This is not mandatory (nor do I think it should be), but if you're casting the deciding vote and nobody else has explained what's wrong with the question it is very helpful to the mod staff and the person whose question was closed) if you explain the reason behind the closure.
Looking at your examples quickly:
How do I make it so that files created in a directory have a certain group ownership?
This is a basic Unix question. While it can be answered here it can also be answered by Google or Wikipedia. If there were some indication of the reason behind this question being related in some way to professional system administration I might have more sympathy for it, but right now to me it looks like a lazy "gimmie" question.
I think closed, with two correct answers, is an appropriate fate, but a pointer to Unix & Linux wouldn't go amiss either.Ubuntu 12.04 updates broke VSFTP
I agree this question is on-topic, and should be kept open.
This is why it takes 5 people to close a question, and also why we have reopen votes.http://stackoverflow.com/questions/14006455/mongo-php-on-ubuntu-12-04
I reject the premise of the statement: "If it can be solved withaptitude" is not an acceptable standard for "Belongs on Server Fault". We have Unix & Linux and Ask Ubuntu for many of these questions.
Incidentally I also reject the question - I would have closed it outright and sent them to the How can I ask better questions on Server Fault? question, told them to do more troubleshooting, and submit the question for reopening with more detail. It's a good start, and may be on topic, but it needs work.http://serverfault.com/questions/460047/open-source-freeware-server-availability-monitoring-app-for-windows-with-web-d and
http://serverfault.com/questions/460019/are-there-any-guis-for-managing-kerberos-principals-on-enterprise-linux should be closed as "Not Constructive". I agree that using "Off Topic" here is confusing.
There is a long-standing precedent for using off-topic for these questions (in fact the standard comment is that shopping questions are "off topic on all Stack Exchange sites"), but Not Constructive better describes the reason the question is being closed.