I am trying to run wildfly-init-debian.sh to run wildfly on starup but when I run the file it gives
"user wildfly does not exist..."
error.
How can I define this user?
The script is almost certainly trying to start WildFly as the debian user wildfly. You will need to create this user and make sure it has correct permissions for your WildFly directories.
The most easy way is to run
useradd wildfly