If I have a question that is on-topic on, say, both Linux & Unix and Ask Ubuntu, may I post it on both sites? And if so, do I need to do anything special?
I personally don't have anything against it if it's done well but the official Stack Exchange policy on intra-StackExchange cross-posting is more clear on the topic:
I don't completely agree with this policy.
I don't want to confuse people too much, but the Internet is bigger than StackExchange sites and most things (be that programming or Ubuntu) have more than one support channel. I essentially don't think it would be fair for me to moderate in a way I don't behave.
A common cross-posting behaviour I engage in is asking for help with web development. I'm a StackOverflow member so [more frequently than I'd like], I'll ask a question on there and immediately ask on IRC (linking to the question on SO). I do this because this is my
With Ubuntu, I used to be a fairly active UbuntuForums poster. When I started here, I would very often post something here or there and then cross-link, or again, use IRC. I still do if it's urgent but thankfully I haven't had many super-serious issues recently.
I think I'd be a massive hypocrite if I slammed every cross-posted question as some sort of Simpsons-did-it-first-duplicate. What makes two diverse StackExchange sites more "special" than disconnected support avenues like Ask Ubuntu is to Ubuntu Forums or IRC? The same mechanics apply: you ask for help; people invest time to help you; you win.
But that doesn't mean I support all sorts of cross-posting; it's incredibly important that questions are maintained. By starting a question anywhere, you're creating a social contract: you're asking people for help and if they see an answered question, they might put [considerable] time into giving you a good answer. If you get an answer somewhere else and don't update your question here, you're wasting our users' time and I'm not okay with that.
My view on basic guidelines would be:
This is slightly different to the path other SE sites tread. If you cross-post something on another site with a different policy, they may well outright delete your thread. That's their choice.
As a deterrent against poor cross-posting, if we notice you cross-posting without taking these steps seriously, we'll give you a warning. Twice and we'll take action to protect our users from you wasting their time.
If you regret your initial choice and want to change sites, I recommend flagging for migration rather than deleting and re-asking, in case someone has seen the question and is preparing an answer.
Unix and Linux's FAQ explicitly says not to cross-post:
So Do not post the same question on both Ask Ubuntu and Unix & Linux. When a question is cross-posted to U&L and other sites, what normally happens is that all but one instance of the question are deleted. You get a warning the first time, and doing it routinely would be considered abuse.
By the way, althought the term “cross-post” is often used, there is technically no cross-posting facility on Stack Exchange. A given question exists on a single site; if you post questions with identical contents, that's a multi-post.