I downloaded the new 1.17 jar and updated my server as I have done numerous times. I received the error below this time around:
Error: LinkageError occurred while loading main class net.minecraft.server.Main
java.lang.UnsupportedClassVersionError: net/minecraft/server/Main has been compiled by a more recent version of the Java Runtime (class file version 60.0), this version of the Java Runtime only recognizes class file versions up to 55.0
I updated my java version using the commands below.
sudo add-apt-repository ppa:linuxuprising/java sudo apt update sudo apt install oracle-java16-installer --install-recommends
After updating it, it started up with no problems.