It does appear SIGUSR1 is special: https://gitlab.gnome.org/GNOME/gdm/blob/master/daemon/gdm-server.c https://gitlab.gnome.org/GNOME/gdm/blob/master/daemon/main.c
Next, please report the problem to the Gnome developers here: https://gitlab.gnome.org/GNOME/gdm/issues and then tell us the new bug ID. ** Changed in: gdm3 (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1782152 Title: GDM blocks SIGUSR1 used in PAM scripts To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdm3/+bug/1782152/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs