Following the instructions on a different post, I have been trying to reindex Spotlight on Yosemite. However, I am stuck now with a "Error: Unknown Indexing State" error. How can i force my iMac to start reindexing everything? I tried following instructions from a different post 8 down vote Has your spotlight been botched? IN short, finder relies on spotlight to find things quickly. This will take a while (5 or so mins) and make your Mac go into "jump-jet" mode with the fans, but: Drop to terminal type in sudo rm -rf /.Spotlight-V100 then sudo rm -rf /.Spotlight-V200 then sudo mdutil -i off / then sudo mdutil -i on / finally sudo mdutil -E / But it seems that I can stop the indexing, but i can't get it to restart it. Argh! if anyone has any suggestions for me to try, please let me know.