Is there an approach to pre-set (better included in the installation package) default general settings?
For example I don’t want client to do image back (too much space needed); do not want to allow automatic upgrade client (may cause problem before testing), etc. With large amount of machines it is very difficult to change it on the web one by one.
Or where are the settings stored on the server side?
Every version is different, if you are referring to the 2.1.X version of UrBackup, in your settings under Image Backups there is a disable check-box. Check to disable Image Backups; you can customize this to where only certain clients perform this with the Separate Client Settings feature.
Under the Server settings of your web-interface, there is a check-box labeled Autoupdate Clients. Make sure that is not checked.