Exclude Spotlight from indexing External Drives and folders

Getting Spotlight to skip indexing particular folders in a fixed drive is as simple as dragging the folders into Spotlight’s Privacy Settings tab. However, in order to get Spotlight to stop indexing external drives (USB drives, external hard disks, etc), the Privacy Settings tab only disables it temporarily – when you remount the volume, indexing begins again.

To avoid Spotlight from indexing an entire volume, create an empty file named .metadata_never_index in the root folder of the volume. If your volume is called MYDATA, for example, open up Terminal and type:

$ touch /Volumes/MYDATA/.metadata_never_index

Spotlight should now skip indexing this volume – as long as this file exists.