A master image is the image of the hard drive/logical disk or partition which you will used to restore the system.
The safest way to create a master image for a system rescue disk is to set the system up, turn it off, then start it up with the R-Drive Image startup version and write the master image file either to a network drive or to a USB disk. Please note that you have to connect the USB disk before you start up the system.
If you are going to create the master image in the same way as a regular image , it is necessary to understand how OEM System Recovery Media searches for the target drives/partitions to restore data to.
Hard drives : OEM System Recovery Media identifies drives by their identity info (vendor+model+revision). So, when creating the master image, avoid connecting the source drive to a non-standard drive controller. It may change the drive name and/or size, making it impossible for OEM System Recovery Media to identify the target drive correctly when restoring data.
Partitions : OEM System Recovery Media identifies partitions by their offset+size and, with lesser priority, by their file system information (file system type and label). if OEM System Recovery Media find one object which properties coincide with those in the master image, it believes that it has found the target partition. If there are several same partitions on different drives, OEM System Recovery Media selects the target partition by its HDD identity info.
Note: When creating the master image, specify the Image split size option on the Image Options panel according to the requirements of the target where you want to store the master image and do not pay attention to the size requirements of the media type you plan to use. When producing the startup disk, R-Drive Image will split the image accordingly.