The majority of questions that are on-topic for Unix & Linux would also be on-topic for Super User. The community there is more specialized and may be better equipped to handle Linux-related questions, but you should remember the general rule that if a question is on-topic for this site, it should not be migrated to another site (even if it would be better there) unless the OP requests it.
The right thing to do is to post a comment like this:
While your question is on-topic for Super User, you may get better answers on Unix & Linux. If you so wish, you may post your question there and then delete it here, or flag your question for migration. Please don't cross-post, though—having the same question on multiple sites at the same time is generally frowned upon.