Crontab, Screen and Java

[dbrazzor]

Hello!

I've searched a lot but still didn't find the solution to my problem

I have a Java application which works perfectly on a detached screen when I run the command "screen -S twitter java -jar /home/pi/Twitter\ Bot\ Server.jar" manually. I want it to be executed at reboot.

I am using crontab to achieve it, so far I have created a script named "launch.sh" (content here : http://pastebin.com/WygEPp0Y) in the home directory (it works when running "sh launch.sh"), and I added this line to crontab : "@reboot sh /home/pi/launcher.sh >/home/pi/logs/cronlog 2>&1".

The problem is that nothing happen at reboot
Does anyone has advice? I would really appreciate it.

Thanks in advance,
dbrazzor

[stderr]

I have a Java application which works perfectly on a detached screen when I run the command "screen -S twitter java -jar /home/pi/Twitter\ Bot\ Server.jar" manually. I want it to be executed at reboot.

I am using crontab to achieve it,

The problem usually involves the environment or permissions when crontab fails. Try doing something simple that could show that it is starting like perhaps printenv into a file. If that makes sense, does java by itself start?

[scruss]

the combination of screen and sudo (?? why) in cron's reduced PATH will be killing it

[dbrazzor]

Thanks for your answers!

stderr : This is what I get when printenv runs with contab : http://pastebin.com/xFkLZs7g
I can get the java application running without screen, it must be the problem

scruss : The application use WiringPi and needs to be executed with sudo, do crontab executes commands with the same permissions? (sorry for my bad knowledge, I'm new to this). Still, nothing happens, even if I remove sudo

Regards,
dbrazzor

[mutley]

As long as you are using root's crontab, you won't need the sudo command. As an FYI, using sudo in a script is not the best approach, you should use sudo to run the actual script if it needs elevated privileges.

It looks like the path may be you problem.
put the full path to the screen / java commands in your script.

[dbrazzor]

Thanks for your answer!

I changed the script (which looks like this now : http://pastebin.com/cEvNm1jM)

But nothing changed, I still don't have any detached screen on reboot

It works perfectly without screen, maybe a problem with the environment?
I saw some posts saying the crontab line should starts with "(. ~/.profile;", can someone explains me what it does and what is the default profile name?

Thanks a lot!

[scruss]

I saw some posts saying the crontab line should starts with "(. ~/.profile;", can someone explains me what it does and what is the default profile name?

That will source the old-style shell profile, which you may not have. It's supposed to set up your PATH so your cron command can find everything. It makes a lot of assumptions.

If you want to start something as root on boot, it can go in /etc/rc.local - but that has some limitations too.

[DougieLawson]

That will source the old-style shell profile, which you may not have. It's supposed to set up your PATH so your cron command can find everything. It makes a lot of assumptions.

If you want to start something as root on boot, it can go in /etc/rc.local - but that has some limitations too.

You could also join the 21st century and write a systemd service file.

viewtopic.php?p=949137#p949137

[scruss]

You could also join the 21st century and write a systemd service file.

One could, but it's not as straightforward as adding a line of shell commands to rc.local when you just need to run something. I'm sure I'll get to systemd when I need something more.

I wasn't, incidentally, recommending the . ~/.profile approach. Just that I've seen it suggested before.