I built out a number of images with Oracle Cloud using Oracle Linux 8. I was facing the trouble that due to the way I configured my instances, Oracle Cloud was not supplying a domain name via DHCP which caused my instances to return a short host name when I ran hostname -f. This in turn caused many scripts to fail, as they could not enumerate a FQDN.

So the answer was actually extremely simple:

echo 'DOMAIN="domain.com"' >> /etc/sysconfig/network
echo machine.domain.com > /etc/hostname
sed -i 's/PRESERVE_HOSTINFO=0/PRESERVE_HOSTINFO=2/g' /etc/oci-hostname.conf
reboot

Also ensure that the entry for the hostname in /etc/hosts references the FQDN first, and the shortname last, or else hostname -f will produce the shortname and not the FQDN