Errors in Upgrade from Fedora 21 to Fedora 22

1. Make sure your current system is up-to-date and backed up

First up, ensure that you have the most up-to-date version of Fedora 21 by updating your system using the Software application, or running the following command in the terminal:

sudo dnf update

2. Install the FedUp tool

Now, open up a Terminal and install FedUp package by using the following command line:

sudo dnf install fedup

3. Start the update with FedUp

Now your system is fully up-to-date, start the upgrade using the following command:

sudo fedup --network 22

This command will tell FedUp to download all the appropriate packages from the Fedora repositories, and prep your system for the upgrade.
4. Reboot, and upgrade

Once the FedUp command from step 3 has completed without errors, reboot your system. In the Fedora Boot Menu (i.e. grub), there will be a menu item “System Upgrade”, select that and press enter.
Boot menu with System Upgrade (fedup) option selected
Boot menu with update option selected

All the appropriate packages and upgrade tasks will now be completed automatically, and when completed you will be able to start using your newly upgraded Fedora system.

# fedup --network 22
setting up repos...
Error: can't get boot images.
The installation repo isn't currently available.
Try again later, or specify a repo using --instrepo.

Using --instrepo To special a repo :

[lanbing@LanBing-PC ~]$ setting up repos...
getting boot images...

Downloading failed: couldn't get boot images: No more mirrors to try.
Last error was: [Errno 14] curl#56 - "Proxy CONNECT aborted"

Change the /etc/yum.conf file to disable Proxy settings ,