https://superuser.com/questions/1143925/how-to-disable-automatic-updates-on-fedora-25
The title is sufficient I think. How can I stop Fedora to automatically download and install system and software updates on restart?
Answer
dnf is a background service that updates the repository metadata automatically.dnf makecache is scheduled to run after every reboot
To disable dnf-makecache.service:
systemctl disable dnf-makecache.service
Also disable the dnf-makecache.timer or the service will be restarted:
systemctl disable dnf-makecache.timer
Regards
Note that you also will need to separately disable packagekit refreshes. This is a known problem and I'm optimistic that we'll get this solved in the next release (but not F25).
gsettings set org.gnome.software download-updates false