This appears to be due to LightDM trying to connect to these X servers as 127.0.0.1:<displaynumber>. I think this means it's trying to use TCP/IP and failing. Since X.Org changed to TCP/IP disabled by default this stopped working. Solution is to just connect to :<displaynumber>.
** Changed in: lightdm Milestone: None => 1.17.4 ** Also affects: lightdm (Ubuntu Wily) Importance: Undecided Status: New ** Also affects: lightdm (Ubuntu Xenial) Importance: Medium Status: Triaged ** Also affects: lightdm (Ubuntu Vivid) Importance: Undecided Status: New ** Changed in: lightdm (Ubuntu Vivid) Status: New => Won't Fix ** Changed in: lightdm (Ubuntu Vivid) Importance: Undecided => Medium ** Changed in: lightdm (Ubuntu Wily) Status: New => Triaged ** Changed in: lightdm (Ubuntu Wily) Importance: Undecided => Medium ** Also affects: lightdm/1.16 Importance: Undecided Status: New ** Changed in: lightdm/1.16 Milestone: None => 1.16.6 ** Changed in: lightdm/1.16 Milestone: 1.16.6 => 1.16.7 ** Changed in: lightdm/1.16 Status: New => Fix Committed ** Changed in: lightdm/1.16 Importance: Undecided => Medium -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1529454 Title: dm-tool add-nested-seat fails To manage notifications about this bug go to: https://bugs.launchpad.net/lightdm/+bug/1529454/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs