The /proc/boot directory

By default, the files from the startup image are placed into a read-only filesystem mounted at /, in a directory called /proc/boot. In a tiny embedded system, for example, this might be used to hold configuration files, or other data files, without the need for a full-blown filesystem manager, and also without the need for additional storage. You can get more information about this by looking at the mkifs command in the Utilities Reference.