How to update OS X using dmg I have multiple Macs and I want to update all those macs using a dmg file. From where I can get the dmg file.And how to update if the minor version difference is more than one. i.e. from 10.10.1 to 10.10.5?
You can get the dmg file from here: https://support.apple.com/downloads/macos

While downloading the dmg please check the system requirement. Because you will need a combo dmg file if you are upgrading from say 10.10.2 to 10.10.5

On detail page of the dmg there is a System Requirements button at the bottom, please check the system requirement from there.