Fedora 26: Fedora is one of the most popular GNU / Linux distributions. It is the result of the Fedora Project, a large community of volunteers and sponsored by Red Hat. The default Fedora environment is GNOME desktop and the default interface is GNOME Shell. Of course it supports other desktop environments such as: KDE, Xfce, LXDE, MATE and Cinnamon released as custom ISO on Fedora spins.
One of the best-known distribution features is that each new version of Fedora is released every six months. The proposed upgrade method is restarted from CD with the new version. The software will check the computer hard drives for older versions of the distribution. If older versions are found, you should choose to re-install or upgrade.
Upgrade via yum / dnf is not recommended, but we'll see below how it happened without any problems:
We upgraded a multi-boot system with Fedora 25, CentOS and Manjaro Linux, on Fedora 26, CentOS and Manjaro. The main boot is under Manjaro as you will see in the picture below. The screenshot was taken after the upgrade of Fedora to 26. 
We ran the grub-mkconfig command into the main boot (Manjaro) to see the new upgraded version of Fedora 26 and the new Kernel.
But let's see how we went through the dnf upgrade.
We will initially install the package 
dnf-plugin-system-upgrade
sudo dnf install dnf-plugin-system-upgrade
and we will download all upgraded packages for the 26 version (releasever = 26):
sudo dnf system-upgrade download --refresh --releasever = 26 --allowerasing
Make sure to accept installing the new RPM-GPG-KEY
When all the packages are down, we can upgrade, which will start after reboot and will take a long time.
sudo dnf system-upgrade reboot
After restarting your computer, all your settings from the previous version will be there, but your operating system will be upgraded to the latest version.
But let's see what's coming with the new Fedora 26 (still under development)
As you can see in the above figure, the Cinnamon version (Gnome has reached the 3.24 version) is in 3.4, while Linux Kernel has been upgraded to 4.11.
You can see what else the new version brings to official webpage.
