Fedora uses the GRUB2 bootloader. By default, a menu is shown to the user for 5 seconds at system boot.
To hide this menu, add the following lines to /etc/default/grub:
GRUB_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT=1
GRUB_HIDDEN_TIMEOUT_QUIET=true
Optionally, you can also disable the graphical appearance by adding this line:
GRUB_TERMINAL=console
You then need to update the GRUB2 configuration file. This is usually located at /boot/grub2/grub.cfg. On UEFI-enabled systems, it’s probably located at /boot/efi/EFI/fedora/grub.cfg. If you’re not sure where it is on your system, there’s usually a symlink to it from within the /etc directory. Run the following command with the correct location:
# grub2-mkconfig -o /boot/grub2/grub.cfg
At system boot, the menu can be accessed by pressing <Esc>. You can give yourself more time to do this by setting GRUB_HIDDEN_TIMEOUT to a higher value (in seconds).