For the impatient, here are the commands:
- sudo dnf upgrade --refresh
- sudo dnf install dnf-plugin-system-upgrade
- sudo dnf system-upgrade download --releasever=29
- sudo dnf system-upgrade reboot
For the more cautious, see the original post in Fedora Magazine: "Upgrading Fedora 27 to Fedora 28" The instructions abpve are the same, with a minor version change.
Full disclosure: I'm a Red Hat associate, but not working in the Fedora space and my upgrade is currently 4585 out of 4597 packages complete. Call me an optimist!