How to Change the World Seed on a Minecraft Java Server
Attention
Create a backup of your server beforehand, as the current world can be lost by changing the world seed.
Open server.properties
Connect to your server via SFTP and open the fileserver.properties.Find the entry
Look for the following entry:level-seed=level-seed=Set the seed
Insert the desired world seed at this point (e.g.level-seed=5101553622029575588).Restart the server
Save the changes and restart the server.
Tip
You can find out the current world seed of an existing world by entering the command /seed in the game.