We Keep Coding

How to configure crontab to run Django command?

I run a Debian 10 system have the following shell file named "update.sh":
#!/bin/bash
cd home/user/djangoprojet
source /env/bin/activate
python manage.py update
I run a root user and set "chmod +x update.sh".
When I run "home/user/djangoprojet/update.sh", executing the script works perfectly.
I now used "crontab -e" to run the script every minute:
* * * * * home/user/djangoprojet/update.sh > testcron.log
However, the script is not executed. When I run "grep CRON /var/log/syslog", I get the following result, which indicates that crontab runs:
Jan 30 15:08:01 vServer CRON[22036]: (root) CMD > (home/user/djangoprojet/update.sh > testcron.log) Jan 30 15:08:01
vServer CRON[22035]: (CRON) info (No MTA installed, discarding output)
The "testcron.log" file, located in the root directory, is empty - although the script would generate an output, if it ran.
Somewhere on StackExchange I also found to execute this command
/bin/sh -c "(export PATH=/usr/bin:/bin; home/user/djangoprojet/update.sh </dev/null)"
which works perfectly.
How can I configure crontab correctly such that my script runs? Thanks!

I now found the solution: I need to use "/home/" instad of "home/" everywhere

Bash script executes Python manually, but not from cron

I've been trying to debug this for a while now and I feel like I've tried everything.
Code is slightly modified with *** for company reasons.
The following executes as expected when run from a session as my local user.
/var/www/****/***/run.sh path_to_my/script.py 2>&1 >> /var/www/****/***/test.log
Where run.sh is just a wrapper for running Python in a virtualenv:
#!/usr/bin/env bash
wd=$(dirname $0)
source ${wd}/virtualenv/bin/activate
python ${wd}/$1
I have placed a print statement inside of the Python main to show that it's being executed.
if __name__ == "__main__":
print("I got in here...")
When running the command as my local user, the log will contain this printed statement. However, when run in cron as:
*/30 * * * * /var/www/****/***/run.sh path_to_my/script.py 2>&1 >> /var/www/****/***/test.log
I do not get any printed statement, nor do I receive any error output from the 2>&1.
My permissions are 755 on both the .sh and .py scripts.
Everything works as expected except when run via cron.
Am I missing something? Does cron not use .bashrc for the crontab user?

First make sure your local cronjob is running by putting the following in the crontab file and check to see if it get written out at /tmp/env.output after a minute or two
* * * * * env > /tmp/env.output
Second make sure the user running the crontab has permission to write to the /var/www/****/***/test.log file
Third try changing your script to
wd=$(dirname $0)
cd $wd
source activate
python ${wd}/$1
Edited: Anders was able to figure out the answer by himself by adding PYTHONPATH to the cron environment: export PYTHONPATH="${PYTHONPATH}:${wd}"

Cronjob can not running after basic configuration

First thing, i'm surely know my python script is not run at all. Because i have 2 python script called checkDB.py and logDHT.py
this is my cron configuration :
# For more information see the manual pages of crontab(5) and cron(8)
#
# m h dom mon dow command
1 * * * * pi /usr/bin/python /home/pi/Sensors_Database/logDHT.py
15 * * * * pi /usr/bin/python /home/pi/Sensors_Database/checkDB.py
and sure i had to give each script chmod+x to make sure its executable, and double check if my script realy have an error but sure my python script is running when i execute it manualy.
also i made setting up the cron on superuser. so can you guys tell me whats happen ? or may be what i miss ?
note: i still have not figure it out why is different running cron under root (super user) and without superuser.
i check with this command :
grep cron /var/log/syslog
no cron job is run, but with this command :
/etc/init.d/cron status
my cron status is running

Script run from crontab leaves an empty file

I've tried to run a script from crontab on my Linux system which is leaving an empty file. When I run the script logged on the terminal, it works fine.
Cron line:
#reboot sleep 1m; /bin/bash /root/start_reader_services
The script "start_reader_services" calls a Python script as below:
/root/java/tag_output >> $TAGS_PATH/tags_$DATE_FILE.log
tag_output basically prints out a series of IDs. The same mechanics used to work when I was sending the stdout to my serial port (tag_output > /dev/ttyO0), but now, writing it to the file from cron, the file is created, but is empty.
As I mentioned, running start_reader_services or any piece of that on command line, it works as expected.
Have done:
- Set bash as cron shell
- Set java environments on cron
As requested:
ls -l /root/java/tag_output
-rwxr-xr-x 1 root root 1981 Aug 6 12:06 /root/java/tag_output
First line of tag output:
#!/usr/bin/python
Any help?

Is it possible that tag_output is writing to stderr instead of stdout? Try redirecting stderr too:
/root/java/tag_output >> $TAGS_PATH/tags_$DATE_FILE.log 2>&1
As an aside, you might also want to quote and use braces with the shell variable expansion; that makes it easier to read and probably a little safer:
/root/java/tag_output >> "${TAGS_PATH}/tags_${DATE_FILE}.log" 2>&1

After initialising and updating the crontab using crontab python and before issuing
cron.write(), give the command,
cron.__reduce__()[2]['lines'] = filter(None,
cron.__reduce__()[2]['lines'])
Doing this will remove the empty lines being printed in Linux crontab.

Crontab not restarting process

I am trying to setup a crontab to run 6 python data scrapers. I am tired of having to restart them manually when one of them fails. When running the following:
> ps -ef | grep python
ubuntu 31537 1 0 13:09 ? 00:00:03 python /home/ubuntu/scrapers/datascraper1.py
etc... I get a list of the datascrapers 1-6 all in the same folder.
I edited my crontab like this:
sudo crontab -e
# m h dom mon dow command
* * * * * pgrep -f /home/ubuntu/scrapers/datascraper1.py || python /home/ubuntu/scrapers/datascraper1.py > test.out
Then I hit control+X to exit and hit yes to save as /tmp/crontab.M6sSxL/crontab .
However it does not work in restarting or even starting datascraper1.py whether I kill the process manually or if the process fails on its own. Next, I tried reloading cron but it still didn't work:
sudo cron reload
Finally I tried removing nohup from the cron statement and that also did not work.
How can I check if a cron.allow or cron.deny file exists?
Also, do I need to add a username before pgrep? I am also not sure what the "> test.out" is doing at the end of the cron statement.
After running
grep CRON /var/log/syslog
to check to see if cron ran at all, I get this output:
ubuntu#ip-172-31-29-12:~$ grep CRON /var/log/syslog
Jan 5 07:01:01 ip-172-31-29-12 CRON[31101]: (root) CMD (pgrep -f datascraper1.py ||
python /home/ubuntu/scrapers/datascraper1.py > test.out)
Jan 5 07:01:01 ip-172-31-29-12 CRON[31100]: (CRON) info (No MTA installed, discarding output)
Jan 5 07:17:01 ip-172-31-29-12 CRON[31115]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Jan 5 08:01:01 ip-172-31-29-12 CRON[31140]: (root) CMD (pgrep -f datascraper1.py || python /home/ubuntu/scrapers/datascraper1.py > test.out)
Since there is evidence of Cron executing the command, there must be something wrong with this command, (note: I added the path to python):
pgrep -f datascraper1.py || /usr/bin/python /home/ubuntu/scrapers/datascraper1.py > test.out
Which is supposed to check to see if datascaper1.py is running, if not then restart it.
Since Cron is literally executing this statement:
(root) CMD (pgrep -f datascraper1.py || python /home/ubuntu/scrapers/datascraper1.py > test.out)
aka
root pgrep -f datascraper1.py
Running the above root command gives me:
The program 'root' is currently not installed. You can install it by typing:
sudo apt-get install root-system-bin
Is there a problem with Cron running commands from root?
Thanks for your help.

First of all, you need to see if cron is working at all.
Add this to your cron file (and ideally delete the python statement for now, to have a clear state)
* * * * * echo `date` >>/home/your_username/hello_cron
This will output the date in the file "hello_cron" every minute. Try this, and if this works, ie you see output every minute, write here and we can troubleshoot further.
You can also look in your system logs to see if cron has ran your command, like so:
grep CRON /var/log/syslog
Btw the >test.out part would redirect the output of the python program to the file test.out. I am not sure why you need the nohup part - this would let the python programs run even if you are logged out - is this what you want?
EDIT: After troubleshooting cron:
The message about no MTA installed means that cron is trying to send you an e-mail with the output of the job but cannot because you dont have an email programm installed:
Maybe this will fix it:
sudo apt-get install postfix
The line invoking the python program in cron is producing some output (an error) so it's in your best interests to see what happens. Look at this tutorial to see how to set your email address: http://www.cyberciti.biz/faq/linux-unix-crontab-change-mailto-settings/
Just in case the tutorial becomes unavailable:
MAILTO:youremail#example.com

You need to add python home to your path at the start of the job, however you have python set up. When you're running it yourself and you type python, it checks where you are, then one level down, then your $PATH. So, python home (where the python binary is) needs to be globally exported for the user that owns the cron (so, put it in a rc script in /etc/rc.d/) or, you need to append the python home to path at the start of the cron job. So,
export PATH=$PATH:<path to python>
Or, write the cron entry as
/usr/bin/python /home/ubuntu/etc/etc
to call it directly. It might not be /usr/bin, run the command
'which python'
to find out.
The 'No MTA' message means you are getting STDERR, which would normally get mailed to the user, but can't because you have no Mail Transfer Agent set up, like mailx, or mutt, so no mail for the user can get delivered from cron, so it is discarded. If you'd like STDERR to go into the log also, at the end, instead of
"command" > test.out
write
"command" 2>&1 > test.out
to redirect STDERR into STDOUT, then redirect both to test.out.