The doubt about missing vm.conf on media server

NBU environment: Master/Media  8.1.1
OS environment: RHEL 6.9

It might be very strange that we stumble across missing vm.conf on some media server that running normally.
What I mean is that the media server can still work fine, i.e. run backup jobs, even without its own vm.conf file.
Note: of course there must be the corresponding SERVER entry in the bp.conf for both media and master side.