Hi @Nyteghost,
if you installed the ISO of mineOS you should have made the password for root yourself, just note to not use root to host servers. Also buildtools.jar might be broken. If you look at it in filezilla or something how big is the file? if it’s really small it is probably broken and you should replace it by one downloaded of spigots own distribution system. I made a small tutorial for it in another post you can find it here