I had to use this when I didn't follow directions on my XCP-NG lab system.
Also a note to Freenas/Truenas users, make sure you "keep" a few old versions when you are upgrading things on your NAS, for exactly the same reasons. Yup, had to roll back on one of my production NAS this summer, nearly had a heart attack when stuff booted back up and none of the shares were accessible.