The launch script for a Minecraft server on Windows, Linux or systemd: memory, JVM flags, auto restart and the eula file, for vanilla, Paper, Purpur, Fabric or Forge alike.
Exactly as it sits on disk: server.jar, paper-1.21.4-100.jar, fabric-server-launch.jar.
Used for both -Xms and -Xmx. Equal values stop the JVM resizing the heap while players are online.
PaperMC's own advice is to try no flags first on a modern JVM, and reach for Aikar's only if the server is stuttering.
Loops the script so a crash brings the server back, with ten seconds to interrupt it.
Off adds --nogui. The window costs memory and shows nothing the console does not.