# Tag Info

29

To edit the root crontab: sudo -i crontab -e put the entries you want in; there's a handy template loaded by crontab that shows you what fields are what. Once you're done and saved out of the crontab editor: exit to get back to the user shell. To reboot the machine at midnight and 8 am, you need the line: 0 0,8 * * * reboot though really, Linux doesn'...

24

Edit this file sudo nano /home/pi/.config/lxsession/LXDE-pi/autostart And add this: @xset s off @xset -dpms @xset s noblank @chromium-browser --kiosk http://google.com/ # load chromium after boot and open the website in full screen mode Then reboot. Chromium should automatically launch in fullscreen mode after the desktop has loaded.

19

By default, the logging for the cron daemon is not enabled in Debian (I assume it is the system you are using). To enable it, please open the file /etc/rsyslog.conf via $vi /etc/rsyslog.conf and uncomment the line # cron.* /var/log/cron.log After that, you need to restart rsyslog via$ /etc/init.d/rsyslog restart and you will ...

12

There are pros and cons on both sides of this argument. On the one hand, by keeping your system up to date you insure that you have the latest bug and security fixes; on the other hand, by being on the bleeding edge you may become the victim of an unfound bug or security hole in one of the updated packages, which can prevent your system from working as ...

8

From man 5 crontab: Step values can be used in conjunction with ranges. Following a range with "/<number>" specifies skips of the number's value through the range. For example, "0-23/2" can be used in the 'hours' field to specify command execution for every other hour (the alternative in the V7 standard is "0,2,4,6,8,10,12,14,16,...

7

Like most Debian based systems, the crontab is stored in /var/spool/cron/crontabs On a different note: Why are you trying to start your program using crontab? This is neither a good nor a standard practice. If you're going through the effort of writing an installer, you should be using an init script so that the user has the ability to issue start/stop/...

6

besides the obvious (removing MAILTO line), you may also try to redirect the output of your scripts to /dev/null, since if the script has any output it will be sent to the user this script belongs to by default. add something like this to the end of offending scripts in crontab: >/dev/null 2>&1 the first part '>/dev/null' redirects stdout, the ...

6

on chromium you can use --start-fullscreen (like F11)

6

There is NO NEED to do anything before a reboot. If you issue a sudo reboot command Linux will manage an orderly shutdown of the software. This is, however, a poor way of ensuring a reliable 24/7 system. If it crashes there is no guarantee the reboot itself would happen. The normal solution would be to use a watchdog timer. The Pi has an inbuilt hardware ...

6

As is typical with crontab issues. The environment is not the same as your user or even a sudo/root shell , and env python3 may not return anything (env simply searches through Instead you should explicitly use the full path of python which can be found either as which python3 or which $(env python3) and use that full path in your crontab (typically /usr/... 5 Did you try to add an entry with crontab -e Looks like you have no crontab entries and therefore the file is not created. 5 I know I'm a little late to the game here, but since I found a reason for this not working for me, I wanted to help others: This happened to me too, and I discovered a resolution yesterday. Check to see if any of the compressed files (particularly all the *.1.gz fiels) have 0 bytes? Technically this file exists, but the script sees it as empty, and ... 5 The ampersand (for sending a process in the background) is not necessary for commands issued to cron via the crontab as processes are already forked. The given examples work fine without the &. Actually the first version shows working parameters as it invokes the python interpreter with the filename of the script to be executed as parameter. 0,30 * * * ... 5 The following is an excerpt from the 'Raspberry Pi: Measure, Record Explore' book. It doesn't have the script for the restarting, but at least it will give you a going over of setting crontab. Consider that we wish to run a Python script every day at 6am. The following command will let us edit the crontab; crontab -e Once run it will open the crontab in ... 5 The easiest way to have something run at boot is via /etc/rc.local. Some systemd based distros (e.g., Arch and Fedora) have stopped including this, although it is easy to implement. Which doesn't matter in this case since currently Raspbian does still have that file. It probably contains something about printing the IP address to console, but don't worry ... 5 To run in foreground you'd need to add DISPLAY=:0: @reboot DISPLAY=:0 \usr\bin\python3 \home\pi\Desktop\photo_frames\get_random_row.py > /logs/cronlog Or open it explicitly with xterm: @reboot DISPLAY=:0 xterm -e \usr\bin\python3 \home\pi\Desktop\photo_frames\get_random_row.py /logs/cronlog Generally if it's Python, you could use logging library ... 5 will the entire system halt until the network is up No. where in the boot-up sequence is crontab activated? Crontabs are managed by cron, a system daemon started by init, which on Raspbian jessie is systemd. Exactly when a service is started in terms of time depends on what it depends on, and a degree of indeterminacy, since things that do not depend ... 5 We can ask cron to tell us what its environment is. Create a shell script in your home directory (~/) as follows (or with the editor of your choice):$ nano ~/envtst.sh Enter/C+P the following in the editor: #!/bin/sh echo "env report follows for user "$USER >> /home/pi/envtst.sh.out env >> /home/pi/envtst.sh.out echo "env report for ... 5 As I understand your question: You have a cron job to reboot your RPi every night at 01:00; e.g. 0 1 * * * sudo reboot (#or something similar; e.g. shutdown -r now) You have a 2nd cron job to restart your app using the @reboot facility in cron; e.g. @reboot /path/to/your/flask/app If you're certain that your 01:00 reboot is being executed successfully, ... 4 The shell used is dash; a POSIX-compliant shell, which is designed to be much smaller and more stable than bash. One could argue that you should be writing cron jobs to be POSIX-compliant. Alternatively, try encapsulating your logic into a script and prepending the shebang #!/usr/bin/env bash 4 Most such cases (where script works in shell but not in cron) are because of environment variables that are different in script. In many case the problems is PATH variable. You could use full paths to all executables you are running in script or modify PATH in first line of your script. To trace such issues, you could start from dumping environment ... 4 Be sure that the crontab file is not executable or writable by other users. You should edit the file with crontab -e filename rather than with a general purpose editor. cron needs to be told to re-read crontabs after a modification thereto, with SIGHUP. I believe (but RTM to be sure) that crontab -e will send the signal but if you use another method to edit ... 4 supervisord is such a monitoring daemon. It can launch processes when it starts (though this can be disabled, so processes are manually started). If a process crashes, it will be restarted. As a bonus, it has a nice web interface: 4 cron scripts most likely lack PATH variable, therefore you have to specify the full path to your executables, that you could easily find using: which ifconfig and which date, and your script might look like this: #!/bin/sh /bin/date >> /media/log/crontest.txt /sbin/ifconfig tun0 >>/media/log/crontest.txt 4 Show us your logrotate.conf. Delete your state file /var/lib/logrotate.status and do logrotate -f /etc/logrotate.conf as root. Post back any error messages. You are running logrotate as a cron job? As root? 4 As others have noted in the comments, you need to redirect the output from the command somewhere. This will write to a file, overwriting the file if it already exists. @reboot python /home/pi/Python27/pimon.py > /path/to/output_file.txt Change > to >> if you want to append to an existing file. Check this link for more information on standard input ... 4 Try to use absolute paths inside your bash script. read ip1 < ip.txt and echo "$ip2" > ip.txt Change ip.txt to /home/pi/ip.txt or something like that. The other thing would be the crontab line itself. Why do you have the "pi" there? It goes: minute hour day_of_month month day_of_week command If you want it to execute with the pi user, just ...

4

The most common error in crontabs seems to be not giving the full paths to programs or data used. Use the which command to find where gpio is stored on your machine (probably /usr/local/bin/gpio) and change the command as follows 15 18 * * * /usr/local/bin/gpio -g write 10 1

4

You never flush the buffer, thus, the info is not being dumped to the file. This is done when the file is closed (you never do it), assigning a buffer size (see this stackoverflow answer and comments or flushing the buffer. To achieve the latter (and the easier IMHO), add before the sleep line: log.flush() It should look like: temp = cpu.temperature ...

4

If you want to run cron jobs with start times relative to sun up/down or twilight then you could use sunwait It will determine the correct time to wait, based on your location's coordinates. Simple example running echo 1 hour before sunrise: # m h dom mon dow command 01 00 * * * /usr/local/bin/sunwait sun up -1:00:00 52.518N 1.475W; /bin/echo "...

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