Hi hiro
Upon booting 98-tc.rules is initially under /tmp because that's how it was saved when tinycore.gz was made.
98-tc.rules just calls /usr/sbin/rebuildfstab when a drive is added or removed from the system, like a USB thumb drive.
If you use the boot code "nofstab" then /etc/fstab is not created and /tmp/98-tc.rules is simply left where it is.
If you do not use the boot code "nofstab" then /etc/fstab is created and /tmp/98-tc.rules is moved to its proper
location (/etc/udev/rules.d/) and the system is told those rules exist.
Without /etc/fstab anyone not in the sudoers list can not mount a drive.