Fun fact: You can use a dry erase marker to erase the writing of a permanent marker. Assuming a smooth surface, scribble the dry erase marker over the permanent mark and erase.
I figured this out almost 25 years ago when my commander was writing in front of our group on a great big whiteboard I had just spent several days putting pinstriping on. Spent an hour or so using a dry erase marker to remove Sharpie permanent marker. I just tried it on a whim since we had nothing to lose, and was pleasantly surprised at how effective it was.
Spray deodorant also does the trick
Any organic solvent will do it. Acetone is ideal, in a metalworking shop Sharpie marks are constantly being cleaned off metal using acetone.
I hate recommending acetone flippantly. Sure, it will definitely take it off, but I'd bet that for a lot of the whiteboards in use today it would also take off the surface of the whiteboard. I do love acetone but it's my solvent of last resort.
Acetone can also dissolve plastics so you don't want to use to remove sharpie marks except on glass or metals (or possibly wood). For anything else 99% rubbing alcohol works pretty well.