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I have a python script that takes sensor data from a DHT11 and inputs the data into MySQL. This file when ran in the terminal on my Raspberry Pi returns the right results: python3 ./Data In which will return successfully upload the data and print something along the lines of:

Writing to Sensor...
Write Complete
1623911938828.7395
[19.0, 65.0]

I have used sudo crontab -eand edited the bottom of the file to */1 * * * * python3 /home/pi/Data.py >> /home/pi/data.log 2> &1. The issue is when this runs there are no new data entries into MySQL, but if I run the script outside of the crontab, it will successfully upload the data to the table. The Cron.log file looks normal to me:

Jun 17 16:25:58 raspberrypi cron[364]: (CRON) INFO (pidfile fd = 3)
Jun 17 16:25:58 raspberrypi cron[364]: (CRON) INFO (Running @reboot jobs)
Jun 17 16:26:01 raspberrypi CRON[615]: (root) CMD (pi /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:26:43 raspberrypi systemd-timesyncd[322]: Synchronized to time server for the first time [2606:4700:f1::123]:123 (2.debian.pool.ntp.org).
Jun 17 16:27:16 raspberrypi CRON[1351]: (root) CMD (pi /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:28:01 raspberrypi CRON[1355]: (root) CMD (pi /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:29:01 raspberrypi CRON[1359]: (root) CMD (pi /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:30:01 raspberrypi CRON[1363]: (root) CMD (pi /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:31:01 raspberrypi CRON[1367]: (root) CMD (pi /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:32:01 raspberrypi CRON[1428]: (root) CMD (pi /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:33:01 raspberrypi CRON[1445]: (root) CMD (pi /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:34:01 raspberrypi CRON[1492]: (root) CMD (pi /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:34:26 raspberrypi crontab[1509]: (root) BEGIN EDIT (root)
Jun 17 16:34:50 raspberrypi crontab[1509]: (root) REPLACE (root)
Jun 17 16:34:50 raspberrypi crontab[1509]: (root) END EDIT (root)
Jun 17 16:35:01 raspberrypi cron[364]: (root) RELOAD (crontabs/root)
Jun 17 16:35:01 raspberrypi CRON[1523]: (root) CMD (python3 /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:36:01 raspberrypi CRON[1549]: (root) CMD (python3 /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:37:01 raspberrypi CRON[1573]: (root) CMD (python3 /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:38:01 raspberrypi CRON[1581]: (root) CMD (python3 /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:39:01 raspberrypi CRON[1594]: (root) CMD (  [ -x /usr/lib/php/sessionclean ] && if [ ! -d /run/systemd/system ]; then /usr/lib/php/sessionclean; fi)
Jun 17 16:39:01 raspberrypi CRON[1595]: (root) CMD (python3 /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:40:01 raspberrypi CRON[1652]: (root) CMD (python3 /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:41:01 raspberrypi CRON[1668]: (root) CMD (python3 /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:41:22 raspberrypi crontab[1680]: (root) BEGIN EDIT (root)
Jun 17 16:42:01 raspberrypi CRON[1694]: (root) CMD (python3 /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:43:01 raspberrypi CRON[1701]: (root) CMD (python3 /home/pi/Data.py >> /home/pi/data.log  2> &1)
Jun 17 16:44:01 raspberrypi CRON[1719]: (root) CMD (python3 /home/pi/Data.py >> /home/pi/data.log  2> &1)

Further, the file has been made executable -rwxr-xr-x 1 pi pi 1.1K Jun 17 13:19 Data.py . What could be the issue?

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  • 1
    Why are you using the root crontab? Do you run the script as root from the terminal? Commented Jun 17, 2021 at 9:03
  • Are there new entries in data.log? How do you authenticate against MySQL? Does your script also run as "real" root (sudo su -)? Commented Jun 17, 2021 at 11:54

1 Answer 1

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1

I think two changes may be needed: 2>&1 (no space), and /usr/bin/python3 instead of python3.

Also, @joan comment: don't use root crontab unless it is needed. Its primary benefit (IMO) is that it gets around potential complications of using sudo in a cron job.

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  • What do I do to not use the root crontab? Sorry am quite new to this Commented Jun 18, 2021 at 1:54
  • @Arch1234: A couple of reasons I believe: 1. It's not considered good security practice, 2. It may cause unexpected results in some applications. Question for you: Did this fix your problem? Commented Jun 18, 2021 at 5:17

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