Is it possible to get information about all actions(views/downloads/outlinks, etc.) for a specific domain?
For example: I have a site whit about 7 domains and I would like to know, which domain is the most successful.
As far as I know, Piwik does not keep track of this since you probably specifically told it to treat your seven different URLs as one single website (see Settings -> Websites).
However, what you could do (depending on how you refer to your site from the various URLs) is simply not to tell Piwik what URLs your site has. That way, Piwik would track the URLs as external referrals to your site and you would be able to see where your visitors come from.
But like I said: Whether this works probably depends on the method you use to refer to your site from your various URLs.
Another option would be to use a custom variable. This would require some coding, though.