The easiest way is to quickly upgrade Fedora through a few simple command lines.
1. Upgrade your existing system to the latest version.
sudo dnf upgrade --refresh
Of course, having proper backups well in advance can be of great benefit.
2. Install the DNF plugin
sudo dnf install dnf-plugin-system-upgrade
3. Start downloading the software for the upgrade
The following command will download the software Fedora28 used for the upgrade:
sudo dnf system-upgrade download --releasever=28
This command will download all the software you used to upgrade. If you have some rarely used software installed, it is recommended that you increase the parameter ‐allowerasing , which will automatically uninstall some software that may have an impact on the upgrade.
4. Reboot and upgrade
After the download is complete, please upgrade via the command below. :
sudo dnf system-upgrade reboot
Please refer to the original text:
https://fedoramagazine.org/upgrading-fedora-27-fedora-28/