1. A method of selecting a subset of settings extracted from one or more virtual machine images, the virtual machine images storing therein values of the settings, the settings used by software executing in virtual machines of the virtual machine images, respectively, the method comprising: selecting a target one of the virtual machine images and obtaining target values of the settings from the target virtual machine image; accessing sample values of the settings, the sample values having been obtained from a plurality of virtual machine images; and forming the subset by identifying similarities and differences of the values between the virtual machine images.