Upgrade from 22 to 22.1: by means of the terminal (emergency measure)

Sometimes upgrading from 22 to 22.1 by means of Update Manager doesn't succeed, for unclear reasons. 
Even in cases when the official upgrade feature has already been made available.

In that case you can do the upgrade as follows, by means of the terminal:

a. Launch a terminal window.
(You can launch a terminal window like this: *Click*)

b. In your sources list, replace the Wilma source (2) by the Xia source (22.1). For that, 
use copy/paste to transfer this line into the terminal (it's one line):

sudo sed -i 's/wilma/xia/g' /etc/apt/sources.list.d/official-package-repositories.list

Press Enter.

Then you update the packages list, like this:

sudo apt-get update

Then you perform the actual upgrade, in this way:

sudo apt-get dist-upgrade

This may take a while.

When it's done: reboot your computer. You're done!