I finally reinstalled my system using the Kubuntu 17.10 64 bits ISO today. It solved the problem.
-- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to network-manager in Ubuntu. https://bugs.launchpad.net/bugs/1721821 Title: Kubuntu 17.10 freezes 50 seconds before KDE Plasma starts Status in network-manager package in Ubuntu: New Bug description: I upgraded my Kubuntu 17.04 to 17.10 four days ago. My PC is booting fast: ~10 seconds to see the greeter. But when I connect to my Plasma session, the greeter is staying ~50 seconds at screen, before Plasma is starting (in ~10 more seconds). There was no problem before upgrading to Kubuntu 17.10. I connected to a terminal session just after having entered my password in the greeter, and I launched the htop command: all I can say is that there is no cpu eating process. The cpu is nearly idle during these 50 seconds. ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: sddm 0.14.0-4ubuntu1 ProcVersionSignature: Ubuntu 4.13.0-12.13-generic 4.13.3 Uname: Linux 4.13.0-12-generic i686 ApportVersion: 2.20.7-0ubuntu2 Architecture: i386 CurrentDesktop: KDE Date: Fri Oct 6 18:13:42 2017 InstallationDate: Installed on 2012-07-31 (1893 days ago) InstallationMedia: Kubuntu 12.04 LTS "Precise Pangolin" - Release i386 (20120423) SourcePackage: sddm 0.14.0-4ubuntu1 UpgradeStatus: Upgraded to artful on 2017-10-02 (3 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1721821/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp