According to my research, the best solution to use ubuntu server as a DVR system would be ZoneMinder. is there any alternatives to zoneminder out there? I'm not really happy it only has a web interface to control/view my cameras. And it doesn't have an option to record video stream non-stop. Am I missing something in its configuration? And the thing I really disappointed, I cant find a way to control my PTZ camera with it. what do manufacturers sell along with their standalone linux powered dvr systems?
As you mentioned the best solution is Zoneminder.
If you are using the 11.10 version of Ubuntu the 1.24.4 version of Zoneminder is there. along with the mythzoneminder to give a friendlier way to watch the videos.
For specific stuff about zoneminder and how it handles the devices I suggest:
Support Page - http://www.zoneminder.com/support