Dear Maintainer, I could reproduce the issue in a minimal bullseye VM. >From my observations I guess the USR2 signal is sent by logrotate:
/etc/logrotate.d/xdm: kill -s USR2 $(cat /var/run/xdm.pid); \ If I read [1] right, then USR2 has a default action of process termination. Therefore is my guess that log rotation is started/finishes too fast and the USR2 signal is sent before xdm replaced the default with its own signal handler. With a package built with the following line moved near the top of the main function I could no more reproduce the issue: (void) Signal (SIGUSR2, ReopenLogFileNotify); Kind regards, Bernhard [1] https://unix.stackexchange.com/questions/38589/why-does-sigusr1-cause-process-to-be-terminated
# Bullseye/testing amd64 qemu VM 2020-01-08 apt update apt dist-upgrade apt install systemd-coredump mc fakeroot xserver-xorg xdm openbox xterm apt build-dep xdm mkdir /home/benutzer/source/xdm/orig -p cd /home/benutzer/source/xdm/orig apt source xdm cd timedatectl set-ntp false timedatectl set-time "2020-01-11 23:59:00" reboot # stay in grub menu two minutes journalctl --no-pager Jan 12 00:00:11 debian systemd[1]: xdm.service: Main process exited, code=killed, status=12/USR2 Jan 12 00:00:11 debian systemd[1]: xdm.service: Failed with result 'signal'. journalctl -u xdm -- Logs begin at Sun 2020-01-12 00:00:11 CET, end at Sun 2020-01-12 00:00:27 CET. -- Jan 12 00:00:11 debian systemd[1]: Starting X-Window Display Manager... Jan 12 00:00:11 debian systemd[1]: Started X-Window Display Manager. Jan 12 00:00:11 debian systemd[1]: xdm.service: Main process exited, code=killed, status=12/USR2 Jan 12 00:00:11 debian systemd[1]: xdm.service: Failed with result 'signal'. systemctl status xdm ● xdm.service - X-Window Display Manager Loaded: loaded (/lib/systemd/system/xdm.service; indirect; vendor preset: enabled) Active: failed (Result: signal) since Sun 2020-01-12 00:00:11 CET; 2min 0s ago Process: 491 ExecStartPre=/bin/sh -c [ "$(cat /etc/X11/default-display-manager 2>/dev/null)" = "/usr/bin/xdm" ] (code=exited, status=0/SUCCESS) Process: 499 ExecStart=/usr/bin/xdm -nodaemon (code=killed, signal=USR2) Main PID: 499 (code=killed, signal=USR2) Jan 12 00:00:11 debian systemd[1]: Starting X-Window Display Manager... Jan 12 00:00:11 debian systemd[1]: Started X-Window Display Manager. Jan 12 00:00:11 debian systemd[1]: xdm.service: Main process exited, code=killed, status=12/USR2 Jan 12 00:00:11 debian systemd[1]: xdm.service: Failed with result 'signal'. ls -lisah /var/log/xdm.log* 393340 0 -rw-r--r-- 1 root root 0 Jan 12 00:00 /var/log/xdm.log 393269 4,0K -rw-r--r-- 1 root root 1,4K Jan 12 00:00 /var/log/xdm.log.1 root@debian:~# journalctl -u xdm -- Logs begin at Sun 2020-01-19 00:00:12 CET, end at Sun 2020-01-19 00:00:21 CET. -- Jan 19 00:00:12 debian systemd[1]: Starting X-Window Display Manager... Jan 19 00:00:12 debian systemd[1]: Started X-Window Display Manager. Jan 19 00:00:12 debian systemd[1]: xdm.service: Main process exited, code=killed, status=12/USR2 Jan 19 00:00:13 debian systemd[1]: xdm.service: Failed with result 'signal'. root@debian:~# ls -lisah /var/log/xdm.log* 393269 0 -rw-r--r-- 1 root root 0 Jan 19 00:00 /var/log/xdm.log 393340 12K -rw-r--r-- 1 root root 8,5K Jan 19 00:00 /var/log/xdm.log.1 393359 4,0K -rw-r--r-- 1 root root 274 Jan 11 23:59 /var/log/xdm.log.2.gz root@debian:~# cat /etc/logrotate.d/xdm /var/log/xdm.log { weekly rotate 52 compress delaycompress notifempty missingok postrotate if [ -r /var/run/xdm.pid ]; then \ kill -s USR2 $(cat /var/run/xdm.pid); \ fi endscript } # vim:set ai et sts=4 sw=4 tw=80: ############# watch -n0.01 kill -s USR2 \$\(cat /var/run/xdm.pid\) systemctl stop xdm rm /var/run/xdm.pid systemctl start xdm --> similar result, xdm is not able to start