Something is wrong with the name resolution service the system which you are trying to upgrade is using. From VarLogDistupgradeMainlog.txt we can see:
2019-04-23 00:26:37,923 DEBUG examining: 'deb http://us.archive.ubuntu.com/ubuntu/ bionic main restricted' 2019-04-23 00:26:37,923 DEBUG verifySourcesListEntry: deb http://us.archive.ubuntu.com/ubuntu/ cosmic main restricted 2019-04-23 00:26:37,923 DEBUG url_downloadable: http://us.archive.ubuntu.com/ubuntu//dists/cosmic/Release 2019-04-23 00:26:37,924 DEBUG s='http' n='us.archive.ubuntu.com' p='/ubuntu//dists/cosmic/Release' q='' f='' 2019-04-23 00:27:07,953 DEBUG error from httplib: '<urlopen error [Errno -2] Name or service not known>' 2019-04-23 00:27:07,953 DEBUG entry '# deb http://us.archive.ubuntu.com/ubuntu/ bionic main restricted' was disabled (no Release file) If you fix the issue resolving us.archive.ubuntu.com then you should be able to upgrade. ** Changed in: ubuntu-release-upgrader (Ubuntu) Status: New => Incomplete ** Summary changed: - crash on do-release-upgrade + release upgrade quits because archive mirror is not resolvable -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1825944 Title: release upgrade quits because archive mirror is not resolvable To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1825944/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
