Spotlight Doesn't Search a Thing

Open Terminal application (Application > Utilities > Terminal) and run this command:

sudo mdutil -a -i

This command will turn on indexing on all volumes except impossible volumes such as DVD volumes and unsupported filesystems volumes. mdutil command is a command to manage the metadata stores used by Spotlight. Every volumes are separated-ly managed. Means for example you can turn on indexing on /home only instead of all volumes.

You can check the status first before simply turning on by running this command:

sudo mdutil -a -s

There is a good side for enabling indexing on few Volumes. It will narrow down search with the area that we want. Definitely we don't have to go through / to search documents in /Volumes/ExternalDisk.

PS: Volumes is not mount points. Volumes can be seen on your desktop. The hard disk icon, Macintosh HD is a volume.

Once you turn on indexing, you can see a slow blinking dot at the spotlight button at the top right corner of your Mac.