We Keep Coding

Raspberry Pi Crontab issue

I'm having trouble running my PHP script over crontab. The script is PHP with python that takes data from DHT22 and adds it to Mysql DataBase, then shows the result on HTML page. When I do it manually works fine.
Here is the line I try to run every minute in crontab:
* * * * * /usr/bin/php /var/www/html/cron/run.php
As I mentioned when I run the script in command line works fine but when I add it to crontab does nothing.
So far I have added Apache2 user to gpio with sudo adduser www-data gpio and also gave permissions to my python file with sudo chmod +x /var/www/html/cron/python.py
When I type: ps -ef | grep cron I get:
root 247 1 0 18:50 ? 00:00:00 /usr/sbin/cron -f
pi 1794 1119 0 19:48 pts/0 00:00:00 grep --color=auto cron
Any help is welcome :)

Simple solution; don't add sudo... just crontab -e

DietPi - running a script manually works - but starting from postboot.d throws I/O error

I'm trying to run a script automatic when booting Raspberry with DietPi.
My script starts a Python3 programm which then at the end starts an external program MP4Box which merges 2 video files to a mp4 in a folder in my lighttp webserver.
When I start the script manually everything works. But when the script starts automatically on boot, when it comes to the external program MP4Box, I get an error:
Cannot open destination file /var/www/Videos/20201222_151210.mp4: I/O Error
Script starting my pythons is "startcam" - which lies in the folder /var/lib/dietpi/postboot.d
#!/bin/sh -e
# Autostart RaspiCam
cd /home/dietpi
rm -f trigger/*
python3 -u record_v0.1.py > record.log 2>&1 &
python3 -u motioninterrupt.py > motion.log 2>&1 &
the readme.txt in postboot.d says:
# /var/lib/dietpi/postboot.d is implemented by DietPi and allows to run scripts at the end of the boot process:
# - /etc/systemd/system/dietpi-postboot.service => /boot/dietpi/postboot => /var/lib/dietpi/postboot.d/*
# There are nearly no restrictions about file names and permissions:
# - All files (besides this "readme.txt" and dot files ".filename") are executed as root user.
# - Execute permissions are automatically added.
# NB: This delays the login prompt by the time the script takes, hence it must not be used for long-term processes, but only for oneshot tasks.
So it should also start my script with root priviledges. And that is the (part of the) Script "record_v0.1.py" that throws the error:
import os
os.system('MP4Box -fps 15 -cat /home/dietpi/b-file001.h264 -cat /home/dietpi/a-file001.h264 -new /var/www/Videos/file001.mp4 -tmp ~ -quiet')
When I start the python programs manually (logged in as root) with:
/var/lib/dietpi/postboot.d/startcam
everythin is OK and instead of the error I get the message:
Appending file /home/dietpi/Videos/b-20201222_153124.h264
No suitable destination track found - creating new one (type vide)
Appending file /home/dietpi/Videos/a-20201222_153124.h264
Saving /var/www/Videos/20201222_153124.mp4: 0.500 secs Interleaving
Thanks for every hint

Contrary to the description, the scripts in postboot.d are not excuted as root. So I changed my script to:
#!/bin/sh -e
# Autostart RaspiCam
cd /home/dietpi
rm -f trigger/*
sudo python3 -u record_v0.1.py > record.log 2>&1 &
sudo python3 -u motioninterrupt.py > motion.log 2>&1 &
Now they are running as root and everything works as wanted.

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.

Raspbian python script at boot keeps failing

Good Day All,
I am trying to run a python script at boot using Rasbian on a Raspberry PI.
I have added the following into crontabt -e:
#reboot /usr/bin/python /home/pi/Midori_Monitor/Main_Midori.py
That did not work.
I then tried adding it to rc.local:
# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
printf "My IP address is %s\n" "$_IP"
fi
/usr/bin/python /home/pi/Midori_Monitor/Main_Midori.py
exit 0
That did not seem to work either. I tried adding the user and group (pi:pi) to both and that did not help.
I don't see a log for the crontab however syslog offers:
Feb 21 13:44:57 raspberrypi /USR/SBIN/CRON[1991]: (pi) CMD (pi:pi /usr/bin/python /home/pi/Midori_Monitor/Main_Midori.py)
Feb 21 13:48:22 raspberrypi /USR/SBIN/CRON[1964]: (pi) CMD (pi:pi /usr/bin/python /home/pi/Midori_Monitor/Main_Midori.py)
Feb 21 13:48:24 raspberrypi /USR/SBIN/CRON[2008]: (pi) CMD (pi:pi /usr/bin/python /home/pi/Midori_Monitor/Main_Midori.py)
Feb 24 07:22:18 raspberrypi /USR/SBIN/CRON[1983]: (pi) CMD (/usr/bin/python /home/pi/Midori_Monitor/Main_Midori.py & )
Feb 24 07:28:13 raspberrypi /USR/SBIN/CRON[1983]: (pi) CMD (/usr/bin/python /home/pi/Midori_Monitor/Main_Midori.py & )
Feb 24 07:34:04 raspberrypi /USR/SBIN/CRON[1993]: (pi) CMD (/usr/bin/python /home/pi/Midori_Monitor/Main_Midori.py )
Any suggestions?

SOLVED - I think the core being here that my script is required to run in a GUI environment.
I found this solution here: https://raspberrypi.stackexchange.com/questions/8734/execute-script-on-start-up
If you want a script to run when you boot into the LXDE environment, you could take a look at this Raspberry Pi forum post:
Navigate to:
etc/xdg/lxsession/LXDE
Open the autostart file in that folder:
sudo nano autostart
Add
#python /path/to/script on a new line.
If you want to run something like a python script, put something like #python mypython.py on a new line. Running a script file would be #./superscript, but for some reason the script runs in an infinite loop (perhaps this will stop that).
Save and exit:
Ctrl+X, Y, Enter
Restart your Raspberry Pi into the LXDE environment.

You added the code after exit 0, so it's never executed!
Use this rc.local:
# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
printf "My IP address is %s\n" "$_IP"
fi
/usr/bin/python /home/pi/Midori_Monitor/Main_Midori.py
exit 0

ubuntu ec2 - run python script at startup with arguments

I have a python script i'd like to start on startup on an ubuntu ec2 instance but im running into troubles.
The script runs in a loop and takes care or exiting when its ready so i shouldn't need to start or stop it after its running.
I've read and tried a lot of approaches with various degrees of success and honestly im confused about whats the best approach. I've tried putting a shell script that starts the python script in /etc/init.d, making it executable and doing update-rc.d to try to get it to run but its failed at every stage.
here's the contents of the script ive tried:
#!/bin/bash
cd ~/Dropbox/Render\ Farm\ 1/appleseed/bin
while :
do
python ./watchfolder18.py -t ./appleseed.cli -u ec2 ../../data/
done
i then did
sudo chmod +x /etc/init.d/script_name
sudo sudo update-rc.d /etc/init.d/script_name defaults
This doesn't seem to run on startup and i cant see why, if i run the command manually it works as expected.
I also tried adding a line to rc.local to start the script but that doesn't seem to work either
Can anybody share what they have found is the simplest way to run a python script in the background with arguments on startup of an ec2 instance.
UPDATE: ----------------------
I've since moved this code to a file called /home/ubuntu/bin/watch_folder_start
#!/bin/bash
cd /home/ubuntu/Dropbox/Render\ Farm\ 1/appleseed/bin
while :
do
python ./watchfolder18.py -t ./appleseed.cli -u ec2 ../../data/
done
and changed my rc.local file to this:
nohup /home/ubuntu/bin/watch_folder_start &
exit 0
Which works when i manually run rc.local but wont fire on startup, i did chmod +x rc.local but that didn't change anything,

Your /etc/init.d/script_name is missing the plumbing that update-rc.d and so on use, and won't properly handle stop, start, and other init-variety commands, so...
For initial experimentation, take advantage of the /etc/init.d/rc.local script (which should be linked to by default from /etc/rc2/S99rc.local). The gets you out of having to worry about the init.d conventions and just add things to /etc/rc.local before the exit 0 at its end.
Additionally, that ~ isn't going to be defined, you'll need to use a full pathname - and furthermore the script will run as root. We'll address how to avoid this if desired in a bit. In any of these, you'll need to replace "whoeveryouare" with something more useful. Also be warned that you may need to prefix the python command with a su command and some arguments to get the process to run with the user id you might need.
You might try (in /etc/rc.local):
( if cd '/home/whoeveryouare/Dropbox/Render Farm 1/appleseed/bin' ; then
while : ; do
# This loop should respawn watchfolder18.py if it dies, but
# ideally one should fix watchfolder18.py and remove this loop.
python ./watchfolder18.py -t ./appleseed.cli -u ec2 ../../data/
done
else
echo warning: could not find watchfolder 1>&2
fi
) &
You could also put all that in a script and just call it from /etc/rc.local.
The first pass is roughly what you had, but if we assume that watchfolder18.py will arrange to avoid dying we can cut it down to:
( cd '/home/whoeveryouare/Dropbox/Render Farm 1/appleseed/bin' \
&& exec python ./watchfolder18.py -t ./appleseed.cli -u ec2 ../../data/ ) &
These aren't all that pretty, but it should let you get your daemon sorted out so you can debug it and so on, then come back to making a proper /etc/init.d or /etc/init script later. Something like this might work in /etc/init/watchfolder.conf, but I'm not yet facile enough to claim this is anything other than a rough stab at it:
# watchfolder - spawner for watchfolder18.py
description "watchfolder program"
start on runlevel [2345]
stop on runlevel [!2345]
script
if cd '/home/whoeveryouare/Dropbox/Render Farm 1/appleseed/bin' ; then
exec python ./watchfolder18.py -t ./appleseed.cli -u ec2 ../../data/0
fi
end script

I found that the best solution in the end was to use 'upstart' and create a file in etc/init called myfile.conf that contained the following
description "watch folder service"
author "Jonathan Topf"
start on startup
stop on shutdown
# Automatically Respawn:
respawn
respawn limit 99 5
script
HOST=`hostname`
chdir /home/ubuntu/Dropbox/Render\ Farm\ 1/appleseed/bin
exec /usr/bin/python ./watchfolder.py -t ./appleseed.cli -u $HOST ../../data/ >> /home/ubuntu/bin/ec2_server.log 2>&1
echo "watch_folder started"
end script
More info on using the upstart system here
http://upstart.ubuntu.com/
https://help.ubuntu.com/community/UbuntuBootupHowto
http://blog.joshsoftware.com/2012/02/14/upstart-scripts-in-ubuntu/