Gfilui

When I run the command to upgrade to Ubuntu 18.04

/usr/lib/ubuntu-release-upgrader/check-new-release-gtk

I get the following error :

/usr/lib/ubuntu-release-upgrader/check-new-release-gtk:30: PyGIWarning: Gtk was imported without specifying a version first. Use gi.require_version('Gtk', '3.0') before import to ensure that the right version gets loaded.
 from gi.repository import Gtk
Checking for a new Ubuntu release
Invalid MIT-MAGIC-COOKIE-1 keyUnable to init server: Could not connect: Connection refused
Invalid MIT-MAGIC-COOKIE-1 keyUnable to init server: Could not connect: Connection refused
/usr/lib/python3/dist-packages/DistUpgrade/DistUpgradeFetcher.py:23: PyGIWarning: Gtk was imported without specifying a version first. Use gi.require_version('Gtk', '3.0') before import to ensure that the right version gets loaded.
 from gi.repository import Gtk, Gdk
Segmentation fault (core dumped)

I am not able to understand how to resolve the above error.

You can upgrade to 18.04 by following this article or just follow my answer. I copied only the necessary parts from the article linked above, so it becomes a little bit easier.

Here we go;

first run these commands, so ubuntu is fully updated. This makes the upgrading to 18.04 easier.

$ sudo apt update 
$ sudo apt upgrade
$ sudo apt dist-upgrade
$ sudo apt autoremove

Then we can start the upgrade. By using the following commands;

$ sudo apt install update-manager-core
$ sudo do-release-upgrade -d

You should see the upgrade start by now. For further info take a look at the article.

source: https://linuxconfig.org/how-to-upgrade-to-ubuntu-18-04-lts-bionic-beaver