`vbetool dpms off` not working from crontab

Ntakwetet

11/12/22, 3:10 PM

I have an old laptop I'm using to host a home Debian server. I'd like to switch the screen off at boot, so I put

@reboot vbetool dpms off

in the root crontab (sudo crontab -e). It looks like it runs as expected (see troubleshooting below) but the screen doesn't switch off. Also, when I run vbetool dpms off from SSH it works as expected.

Do anyone have any suggestion?

Troubleshooting results following this answer. Please ask if more details are necessary.

Look at the logs (boot at 10:00:00)

sudo cat /var/log/cron.log:

...
Jul 12 10:00:00 my_hostname cron[457]: (CRON) INFO (pidfile fd = 3)
Jul 12 10:00:00 my_hostname anacron[461]: Anacron 2.3 started on 2021-07-12
Jul 12 10:00:00 my_hostname anacron[461]: Normal exit (0 jobs run)
Jul 12 10:00:00 my_hostname cron[457]: (CRON) INFO (Running @reboot jobs)
Jul 12 10:00:01 my_hostname CRON[487]: (root) CMD (vbetool dpms off)
Jul 12 10:00:01 my_hostname CRON[480]: (CRON) info (No MTA installed, discarding output)
Jul 12 10:00:05 my_hostname systemd-timesyncd[515]: Synchronized to time server for the first time 192.168.178.1:123 (192.168.178.1).

sudo cat /var/log/syslog:

...
Jul 12 10:00:00 my_hostname systemd[1]: Started Trigger anacron every hour.
Jul 12 10:00:00 my_hostname cron[457]: (CRON) INFO (pidfile fd = 3)
Jul 12 10:00:00 my_hostname systemd[1]: Started Run anacron jobs.
Jul 12 10:00:00 my_hostname anacron[461]: Anacron 2.3 started on 2021-07-12
Jul 12 10:00:00 my_hostname anacron[461]: Normal exit (0 jobs run)
Jul 12 10:00:00 my_hostname cron[457]: (CRON) INFO (Running @reboot jobs)
Jul 12 10:00:00 my_hostname systemd[1]: anacron.service: Succeeded.

Check that cron is running

ps -ef | grep cron | grep -v grep outputs

root       474     1  0 10:00 ?        00:00:00 /usr/sbin/cron -f

The last command in my crontab doesn't run

The file ends with an empty line.

Command output

I edited the command to

@reboot vbetool dpms off &>/tmp/mycrontablog.log

but mycrontablog remains empty.

166

0 + 1

debian

cron

Michael Hampton

11/12/22, 3:19 PM

This question appears to be off topic: We don't accept home computer questions. You may be able to get help at our sister site [unix.se].

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: `vbetool dpms off` not working from crontab

TH: `vbetool dpms off` ไม่ทำงานจาก crontab

RO: `vbetool dpms off` nu funcționează din crontab

RU: `vbetool dpms off` не работает из crontab

VI: `vbetool dpms off` không hoạt động từ crontab

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