I tried this both with an Ubuntu desktop install of 18.04 LTS and an lxc cloud image of 18.04 LTS and during neither upgrade process did I encounter the error described in this bug report. Here's some relevant information from the lxc upgrade.
ubuntu@gorgeous-molly:~$ tail /var/log/dist-upgrade/screenlog.0 To finish the upgrade, a restart is required. If you select 'y' the system will be restarted. Continue [yN] y W: molly-guard: SSH session detected! Please type in hostname of the machine to reboot: Good thing I asked; I won't reboot gorgeous-molly ... === Command detached from window (Tue Aug 4 03:29:45 2020) === ubuntu@gorgeous-molly:~$ cat /etc/apt/sources.list ## Note, this file is written by cloud-init on first boot of an instance ## modifications made here will not survive a re-bundle. ## if you wish to make changes you can: ## a.) add 'apt_preserve_sources_list: true' to /etc/cloud/cloud.cfg ## or do the same in user-data ## b.) add sources in /etc/apt/sources.list.d ## c.) make changes to template file /etc/cloud/templates/sources.list.tmpl # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://192.168.10.7/ubuntu focal main restricted # deb-src http://192.168.10.7/ubuntu bionic main restricted ## Major bug fix updates produced after the final release of the ## distribution. deb http://192.168.10.7/ubuntu focal-updates main restricted # deb-src http://192.168.10.7/ubuntu bionic-updates main restricted ... -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1888916 Title: upgrade from bionic to focal a server with molly-guard moves back sources.list to bionic entries To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1888916/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
