15.04 Vivid Vervet won't boot after uninstalling lightdm

[Joyce]

We've been trying to figure out how to disable the login screen on 15.04 Vivid Vervet. Our method of doing this on 14.04 was to uninstall lightdm. If we do this on 15.04, however, the system won't boot. :( The main error seems to be: "Failed to isolate default target, freezing." (I have a picture of this, if there is a way to upload one.)

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1441883/+editstatus and add the package name in the text box next to the word Package.

[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

[Martin Pitt (pitti)]

This is due to xdiagnose's

Requires=display-manager.service
OnFailure=failsafe-graphical.target

[Martin Pitt (pitti)]

Didier kindly offered to work on the xdiagnose part. It's not yet clear whether we also need to change lightdm.

[Didier Roche (didrocks)]

Done, now xdiagnose only triggers if an installed display manager is configured as default but couldn't start. This should fix your boot issue.

We won't fail graphical.target anymore if the only available dm was uninstalled, however, I do recommend you set then your default target to multi-user.target (case on a server system for instance).

The lightdm part would be interesting to ensure /e/X/d-d-m is empty, but not required.

[Launchpad Janitor (janitor)]

This bug was fixed in the package xdiagnose - 3.7.2

---------------
xdiagnose (3.7.2) vivid; urgency=medium

  * Only fallback to xdiagnose on systemd if an installed default display
    manager is configured. Do not fail graphical.target without any dm.
    (LP: #1441883)
 -- Didier Roche <email address hidden> Thu, 09 Apr 2015 10:38:15 +0200

[Joyce (joyce-g)]

Wow, that was fast! Thank you!