Originally posted by countgreen:

Originally posted by Schmowu:

-exit server

-create world in a singelplayer game with the seed you want

-start server with this world

Does this work for headless servers too?

Yes should work fine, just make sure your .bat file or startup file for the game references the new world file.
world files are generally saved in "C:\Users\%userprofile%\AppData\LocalLow\IronGate\Valheim\worlds"