Since executing commands through db rules requires service desk agent on the other side, it depends on whether you can successfully run agent on a linux machine. Officially it is not supported but you could give a try.
However OVSD also support "update to an external system" through db rules. When conditions are met you could have a rule that will contact a web page on the linux machine and upon contact a command could be executed there. It's the safe bet (it is trivial to make it work) but I don't know how secure it is. Obviously there should be an access list in order only application server could hit that url on the linux machine.
Thanks King George for your answer. Id like the second option. Could you pls tell me where I can get some documentation about this issue "update to an external system". Could be easy if Id have an linux agent, but... My real problem is make the integration of HP Service Desk with C.A. Harvest, in order to solve my Itil release mgmt process. I guess more people have the same problem and Im accepting suggestions. Rgds, Rubem