Thank you, Murray. Now I have two question. First, as Lallement pointed out, it was the Xorg/ppa that prevented the upgrade. I have installed the newest version of Xorg with apt-get install command. So can I believe the clog is eliminated? Second, if there still remains some ppa, how do I know what ppa have been installed in the system? further，how do I check the ppa's url that would be needed when remove the ppa with the tool ppa-purge. I hope I make myself clear. I am still getting used to the Ubuntu. Thanks again.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1791208 Title: Fail to upgrade to 18.04LTS from 16.04LTS To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1791208/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
