Created attachment 156523 [details] Journal for the boot of Fedora-KDE-Live-x86_64-38-20230218.n.0.iso on bare metal in which I saw the black screen problem twice SUMMARY I booted the Fedora 38 KDE Plasma live image Fedora-KDE-Live-x86_64-38-20230218.n.0.iso in a QEMU/KVM VM in GNOME Boxes with 3 GB RAM and 3D acceleration disabled using the llvmpipe driver in a Fedora 37 KDE Plasma installation. I noticed that Switch User was shown in the Leave menu of the Application Launcher menu in Plasma 5.27.0. The Switch User option had been missing in previous Plasma versions. When I selected Switch User, a black screen occurred. I tried to switch VTs by clicking on ctrl+alt+f2, ctrl+alt+f3 in the Keyboard menu in GNOME Boxes but the VT logins didn't appear. I shutdown the VM. I booted Fedora-KDE-Live-x86_64-38-20230218.n.0.iso from a USB flash drive written with Fedora Media Writer on bare metal with sysrq_always_enabled on the kernel command line. When I selected Switch User, a black screen occurred with a mouse cursor that I could move for a second then froze. I pressed sysrq+alt+e to stop all processes which restarted Plasma. The journal around the time of the black screen showed sddm-helper exited with the error code 5 and sddm "Couldn't initiate jump to VT 0: No such device or address" I didn't think there was a VT 0 which might be the reason for the problem. Feb 19 15:51:15 systemd[1]: Started session-c1.scope - Session c1 of User sddm. Feb 19 15:51:15 audit[2754]: USER_START pid=2754 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:session_open grantors=pam_unix,pam_systemd acct="sddm" exe="/usr/libexec/sddm-helper" hostname=localhost-live addr=? terminal=/dev/tty1 res=success' Feb 19 15:51:15 sddm-helper[2754]: pam_unix(sddm-greeter:session): session closed for user sddm Feb 19 15:51:15 audit[2754]: USER_END pid=2754 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:session_close grantors=pam_unix,pam_systemd acct="sddm" exe="/usr/libexec/sddm-helper" hostname=localhost-live addr=? terminal=/dev/tty1 res=success' Feb 19 15:51:15 audit[2754]: CRED_DISP pid=2754 uid=0 auid=4294967295 ses=4294967295 subj=system_u:system_r:xdm_t:s0-s0:c0.c1023 msg='op=PAM:setcred grantors=pam_permit acct="sddm" exe="/usr/libexec/sddm-helper" hostname=localhost-live addr=? terminal=/dev/tty1 res=success' Feb 19 15:51:15 systemd[1]: session-c1.scope: Deactivated successfully. Feb 19 15:51:15 sddm[1426]: Auth: sddm-helper exited with 5 Feb 19 15:51:15 sddm[1426]: Couldn't initiate jump to VT 0: No such device or address Feb 19 15:51:15 systemd-logind[1241]: Session c1 logged out. Waiting for processes to exit. Feb 19 15:51:15 systemd-logind[1241]: Removed session c1. I'll attach the journal for the boot in which I saw the black screen problem twice with the same sddm errors. I'm not sure if Switch User was intended to be enabled again. Plasma might have been trying to start sddm on VT 0 which didn't exist, or the problem might be with sddm. Selecting Switch User resulted in a black screen 6/8 times. I had switched to VT2 in VMs and logged in as the liveuser user before selecting Switch User in the two cases when the lock screen appeared instead of a black screen. STEPS TO REPRODUCE 1. Download Fedora-KDE-Live-x86_64-38-20230218.n.0.iso from https://koji.fedoraproject.org/koji/buildinfo?buildID=2154783 2. boot Fedora-KDE-Live-x86_64-38-20230218.n.0.iso in a QEMU/KVM VM in GNOME Boxes with 3 GB RAM and 3D acceleration disabled or on bare metal 3. in the VM case, I disabled automatic login from sddm in System Settings. I'm not sure if this is needed. 4. Select the Application Launcher menu in the lower left corner of Plasma 5.27.0 on Wayland 5. Select the Leave menu 6. Select Switch User OBSERVED RESULT Selecting Switch User in Plasma 5.27.0 in F38 resulted in a black screen with sddm errors EXPECTED RESULT sddm would appear normally without a black screen SOFTWARE/OS VERSIONS Linux/KDE Plasma: Fedora 38 (available in About System) KDE Plasma Version: 5.27.0 KDE Frameworks Version: 5.103.0 Qt Version: 5.15.8 ADDITIONAL INFORMATION Switch User doesn't appear in the Leave menu in Plasma 5.27.0 of my Fedora 37 KDE Plasma installation. I reported this problem at https://bugzilla.redhat.com/show_bug.cgi?id=2171316 There's a report about user switching problems involving two users at https://github.com/sddm/sddm/issues/1660
JFYI the "Switch User" button being missing is due to Fedora packaging, because at the time user switching was broken. Apparently it still is but the button is visible again, which may be a bug in Fedora's packaging for F38, or it may be an intentional change and the feature is supposed to be working now, but isn't for some reason. I'll investigate.
Per comments in https://bugzilla.redhat.com/show_bug.cgi?id=2171316, looks like this was caused by a packaging bug. I'll see if I can track down the bug report for user switching being broken in a general sense.
SDDM issue appears to be https://github.com/sddm/sddm/issues/1660.
The lines disabling user switching were removed by https://pagure.io/fedora-kde/kde-settings/c/c48b87a6c5447b9c9b2febe96bf94feae9ad5183?branch=rawhide in kde-settings-38.0-1.fc38 https://koji.fedoraproject.org/koji/buildinfo?buildID=2150810 That change was reverted due to this problem by https://pagure.io/fedora-kde/kde-settings/c/abdb7005d5e5d8b3ccdc84ffab5bd37b0973d36c in kde-settings-38.1-1.fc38 https://koji.fedoraproject.org/koji/buildinfo?buildID=2156292 Switch User isn't shown in the Leave menu of the Application Launcher menu in Fedora-KDE-Live-x86_64-38-20230221.n.1.iso. The underlying problem seems to be in sddm at the link mentioned previously. Thanks.