My Ubuntu laptop recently runs into a power-off issue. Every time when I shutdown or reboot the machine, it stuck at blank screen with text message “systemd-shutdown: waiting for process: crond” for more than a minute.
According to the keyword ‘crond‘, it has something to do with the cron schedule job. And, thanks to this thread, user may run the command below to list all current schedule cron jobs:
find /etc/cron* -type f | xargs ls -ltr
And there you’ll find that the schedule job ‘/etc/cron.d/collect‘ tries to run an unknown crond binary under ‘/var/tmp’ every 10th minute (e.g., 5:10, 5:20, 5:30 …). So the problem may not occur when shutdown/reboot within a few minutes after login.
The /var/tmp directory stores temporary files or folders that are preserved between system reboots. According to @bird7676 in that thread, the files were probably created by Free Download Manager.
If you don’t use and have removed the Free Download Manager, simply remove these temporary files as well as the schedule job.
To do so, either use a system cleaner (e.g., BleachBit), or press Ctrl+Alt+T on keyboard to open terminal and run command below to remove the files:
sudo rm /etc/cron.d/collect /var/tmp/crond /var/tmp/bs
If the app is important for you, you may run ‘
mv‘ command to move the files to another location or backup unfinished downloads before deleting them.
NOTE: while the binary may be still running though you have removed the file, you may need to shutdown/reboot twice to check if the problem is fixed.
I’ve run into this problem a few times with mysql. However, it seems to be fixed now. I assume it was fixed in an update.