In update-manager I see error "no internet connection", but it isn't true. And update of Ubuntu is no possible for me

[Pavol]

software-properties-gtk probably doesn't work correct too.
I am desperate. Update of Ubuntu doesn't work for me :(.
I use Ubuntu with Cinnamon graphical interface.
I reinstalled software-propertie and software-propertie via Synaptic, but it doesn't help me.
I have Slovak language in Ubuntu.
I send you more screen-shots.
(you support only one file in attachment, I send you screen-shots in zip file)

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: ubuntu-release-upgrader-core 1:17.10.11
ProcVersionSignature: Ubuntu 4.13.0-41.46-generic 4.13.16
Uname: Linux 4.13.0-41-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.8
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: X-Cinnamon
Date: Thu May 17 17:29:08 2018
InstallationDate: Installed on 2016-12-03 (529 days ago)
InstallationMedia: Ubuntu-GNOME 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160720)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=sk_SK
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=sk_SK.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to artful on 2018-05-17 (0 days ago)
VarLogDistupgradeAptlog:
 Log time: 2018-05-17 16:20:23.507926
 Log time: 2018-05-17 16:20:35.638775
 Log time: 2018-05-17 16:24:37.386152
VarLogDistupgradeTermlog:

[dino99 (9d9)]

use 'ppa-purge' with each installed ppa, to get genuine package version. Then cleanup /etc/apt/sources.list to only use 'bionic' entries.

Also run 'gtkorphan' to purge old/un-needed packages; then reboot and update again.

[Pavol (pritel)]

Thank you very much for answer dino99.
I used gtkorphan.
But help me information only on this link
https://itsfoss.com/failed-to-download-repository-information-ubuntu-13-04/

Can you (=Ubuntu developers) repair in next update of Ubuntu all issues with updates full resales and applications? It doesn't work correct and the same issue has a lot of people.

[Jean-Baptiste Lallement (jibel)]

Thanks for your report.

Disregard dino99 comment, it is incorrect and misleading.

One of the reason of the upgrade failure are invalid entries in /etc/sources.list that point to a no longer available release:

deb http://archive.ubuntu.com/ubuntu zesty main universe restricted multiverse
deb-src http://archive.ubuntu.com/ubuntu zesty main universe restricted multiverse #Added by software-properties
deb http://security.ubuntu.com/ubuntu/ zesty-security main restricted multiverse universe
deb http://archive.ubuntu.com/ubuntu zesty-updates main restricted multiverse universe

Besides these duplicates the lines for artful and you can just remove them then attempt the upgrade again. If it fails again then don't hesitate to file another report.

[Pavol (pritel)]

Jean, thank you very much for help!
Now I have successfully installed Ubuntu 18.04!
It is perfect release: light and very quick OS.

But I see other bugs:
- in login manager, when I choose other graphical interface / environment, after login into, I see empty screen only with background picture. Developer team of Ubuntu probably never tested Ubuntu 18.04 for switch on other graphical interfaces

- Ubuntu Software is no possible for use. It work on experimental Snap packages. Installation of applications is no possible