Q:

Synaptic not launching on Ubuntu 17.10

I just installed Ubuntu 17.10. Everything seems to be working quite okay, except that I'm unable to use Synaptic. I installed it with (apparently) no problems, but when I click its icon, nothing happens.
Trying from the terminal this is the error I get:
No protocol specified
Unable to init server: Could not connect: Connection refused
(synaptic:3572): Gtk-WARNING **: cannot open display:

Any idea what this means? 
Thanks in advance for the support. 

A:

You can use Synaptic (or any other application that needs to run as root) under Wayland by first entering this command in the terminal:
xhost +si:localuser:root

A:

You probably logged in using the default Wayland session. Wayland does not allow gui applications to run in superuser mode like Synaptic. If you really want to use this tool you have to login using the Xorg session.

