Stack Exchange network consists of 177 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
When I need to ask a Linux related question, I normally look at the activity on the related unix.se and sf tags to decide where to post it.
I read in a previous question that cross-posting might be okay if the site is beta (is unix.se still beta?)
The context of the question is important. If you substitute your-tag for rsync in this question and it's answers then you should get a feel for what goes where. There is though considerable overlap.
Unix and Linux was launched from beta some time ago.