Total 'implies' the size on disk that these files in this directory are taking up. So, a ls -lh /tmp returns something that looks like:
ls -lh /tmp
This should be the 'sum total' of all the files in that directory and what space they take up.
You find process ID's with 'ps' or 'top' generally speaking; there are other ways but those are likely the answers you are looking for.
I actually have no idea if you can integrate active directory after DNS is configured, but my quick (completely unfounded) guess would be that you can with quite a bit of work. You probably will want to consult a book on Active Directory and Linux or an online resource to see if it mentions it.
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