After upgrading to Kubuntu 18.10, my virtual machine was no longer able to connect to the Internet. It turned out that this problem had already been reported on Fedora:
Once I changed the firewalld configuration (etc/firewalld/firewalld.conf) to use the iptables backend as suggested in that bug report, the virtual machine could connect to the Internet again.
I upgraded a desktop machine from Debian Squeeze to Debian Wheezy. After the upgrade, the power button was mapped to a suspend action, instead of a shutdown as in Debian Squeeze.
In order to map the power button to a shutdown action, I had to do the following;
'nothing' by means of dconf (for all users)
2) Add a new section
[org.gnome.settings-daemon.plugins.power] with the line