Thanks for taking the time to report a bug and help make Ubuntu better. In this case it looks like you have a probable transient network error, as the dist-upgrade log is filled with messages like the following:
'W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/vivid/universe/source/Sources Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1360:8c01::19). - connect (101: Network is unreachable) [IP: 2001:67c:1360:8c01::19 80] which indicates that update-manager could not reach http://archive.ubuntu.com. Should the problem continue to exist, you would need to contact your Internet Service Provider. Thanks. ** Information type changed from Private Security to Public -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1448527 Title: i dnot know excatly To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1448527/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
