I believe I found a solution (or at least, a temporary workaround until the potential bug is fixed). It seemed the bug was introduced in 4.15.0-24, as 4.15.0-23 works fine. I'm running an up-to-date 18.04 system on top of a Lenovo ThinkPad Yoga.
I would get a blank screen with both GDM and LightDM until I started switching virtual terminals or typing my login info, at which point, it would just start up seemingly at random. I set systemd to boot to multi- user instead of graphical, and ran 'startx' and experienced the exact same delay. I took a look at the startx script source and I traced it down to a call to /usr/bin/mcookie which generates a magic number to be used with xauth. According to the BUGS section in the mcookie manpage, it states that mcookie assumes that "none of the randomness sources will block." Sure enough, doing an strace on mcookie shows it hangs at a call to getrandom(), which I'm assuming (my knowledge is a little fuzzy here) means that entropy is too low for getrandom() to generate a number. Moving the mouse around, typing a few characters or switching virtual terminals, to my knowledge, all generate some entropy so that finally when there's enough, getrandom() returns a number to mcookie, thus allowing xorg to start. TL;DR: I installed 'haveged' from the repo, which, as far as I understand, adds to the entropy on boot, allowing xorg to start without any delay. My next step is to take a look at the changelog between kernel releases and see what I can come up with as a potential cause, but I figured I would post what I've found so that others may benefit in the meantime. -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gdm3 in Ubuntu. https://bugs.launchpad.net/bugs/1779476 Title: Ubuntu 18.04: gdm3 does not switch to graphics after update To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1779476/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
