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 Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1779476 Title: Ubuntu 18.04: gdm3 does not switch to graphics after update Status in gdm3 package in Ubuntu: Incomplete Status in linux package in Ubuntu: Incomplete Bug description: After update of gdm and kernel gdm3 no longer enables graphics. What happens: ============= With and without: WaylandEnable=false in /etc/gdm3/custom.conf gdm3 does not switch to graphics. In both cases I case the X process running (Xwayland or Xorg) but no vt has it. lightdm does work, but barely. It takes up to a minute to get to the login screen. What I expected to happen: ========================== gdm3 switching to graphics in ~20 after boot like pre-update. Release: ======== $ lsb_release -rd Description: Ubuntu 18.04 LTS Release: 18.04 $ apt-cache policy kernel-common gdm3 lightdm xorg xwayland kernel-common: Installed: (none) Candidate: 13.018+nmu1 Version table: 13.018+nmu1 500 500 http://us.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages 500 http://us.archive.ubuntu.com/ubuntu bionic/universe i386 Packages gdm3: Installed: 3.28.2-0ubuntu1.3 Candidate: 3.28.2-0ubuntu1.3 Version table: *** 3.28.2-0ubuntu1.3 500 500 http://us.archive.ubuntu.com/ubuntu bionic-proposed/main amd64 Packages 100 /var/lib/dpkg/status 3.28.2-0ubuntu1.2 500 500 http://us.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages 3.28.0-0ubuntu1 500 500 http://us.archive.ubuntu.com/ubuntu bionic/main amd64 Packages lightdm: Installed: 1.26.0-0ubuntu1 Candidate: 1.26.0-0ubuntu1 Version table: *** 1.26.0-0ubuntu1 500 500 http://us.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages 100 /var/lib/dpkg/status xorg: Installed: 1:7.7+19ubuntu7 Candidate: 1:7.7+19ubuntu7 Version table: *** 1:7.7+19ubuntu7 500 500 http://us.archive.ubuntu.com/ubuntu bionic/main amd64 Packages 100 /var/lib/dpkg/status xwayland: Installed: 2:1.19.6-1ubuntu4 Candidate: 2:1.19.6-1ubuntu4 Version table: *** 2:1.19.6-1ubuntu4 500 500 http://us.archive.ubuntu.com/ubuntu bionic/main amd64 Packages 100 /var/lib/dpkg/status Attaching journalctl -b. --- ProblemType: Bug ApportVersion: 2.20.9-0ubuntu7.2 Architecture: amd64 CurrentDesktop: ubuntu:GNOME DistroRelease: Ubuntu 18.04 EcryptfsInUse: Yes InstallationDate: Installed on 2016-08-27 (673 days ago) InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719) NonfreeKernelModules: wl Package: gdm3 3.28.2-0ubuntu1.3 PackageArchitecture: amd64 ProcVersionSignature: Ubuntu 4.15.0-24.26-generic 4.15.18 Tags: bionic package-from-proposed Uname: Linux 4.15.0-24-generic x86_64 UpgradeStatus: Upgraded to bionic on 2018-05-05 (58 days ago) UserGroups: adm cdrom dip docker lpadmin plugdev sambashare sudo _MarkForUpload: True mtime.conffile..etc.gdm3.custom.conf: 2018-06-30T11:12:29.280424 --- ProblemType: Bug ApportVersion: 2.20.9-0ubuntu7.2 Architecture: amd64 CurrentDesktop: ubuntu:GNOME DistroRelease: Ubuntu 18.04 EcryptfsInUse: Yes InstallationDate: Installed on 2016-08-27 (674 days ago) InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719) NonfreeKernelModules: wl Package: linux PackageArchitecture: amd64 ProcVersionSignature: Ubuntu 4.15.0-24.26-generic 4.15.18 Tags: bionic package-from-proposed Uname: Linux 4.15.0-24-generic x86_64 UpgradeStatus: Upgraded to bionic on 2018-05-05 (58 days ago) UserGroups: adm cdrom dip docker lpadmin plugdev sambashare sudo _MarkForUpload: True modified.conffile..etc.gdm3.custom.conf: [modified] mtime.conffile..etc.gdm3.custom.conf: 2018-06-30T11:12:29.280424 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1779476/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
