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I've got a few Python based servers that I need to run, and would like them to start automatically when I start my Ubuntu Server box. What is the best way to execute them like this?

I was hoping I could write a Bash script and use Screen to get them running in the background, where I can check on them every now and then, but where as

echo screen -d -m python

works just fine,

echo screen -d -m `sudo python /home/matt/tornadoServer/tornadoDeploy.py`

doesn't, with no error messages. Is that something to do with the spaces? Even though I did surround it with backquotes? I also tried:

WEB="screen -d -m `sudo python /home/matt/tornadoServer/tornadoDeploy.py`"
echo $WEB

As a way of escaping the spaces, but no luck. What's Bash scripting way to do this?

And, once the Bash script works, where can I put it to make it execute on startup?

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Are you trying to execute tornadoDeploy.py in the screen session, or are you trying to have screen run the command tornadoDeploy.py prints out, because that's what backquotes do: run the quoted command immediately, collect its standard output, replace the quoted command with its output, then finally run the full command with replaced text. – DerfK Dec 26 '10 at 20:54
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4 Answers

up vote 1 down vote

Its failing because sudo is prompting for a password. Since there's no TTY open, its just waiting for you to enter one--or may, in fact, be instantly failing. If you're running this as root, you don't need to launch it as sudo.

However, what you likely want to do is alter tornadoDeploy.py to daemonize itself--that is, to detach itself, so that its not running with an open session. The python-daemonize library provides easy tools to allow you to do this. This eliminates having to deal with screen, while still allowing you to daemonize the process.

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Put 

sudo -n python /home/matt/tornadoServer/tornadoDeploy.py &

into the file /etc/rc.d/rc.local. Or whatever the equivalent is for your distribution.

Assuming your script is a well behaved daemon and that you have set up sudo to not require a password for running your script.

Read this about startup scripts and this about a python daemon library. Also, don't you have to run tornado behind a real http server?

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Oh yes, apparently I am indeed meant to run it behind an http server. I'm new at deploying my webservers, don't I still have to run the tornadoDeploy.py (which runs the server) just not on port 80? Can I get nginx to do that for me somehow? – DizzyDoo Dec 26 '10 at 17:41
I don't think so unless your tornado code can handle getting called like a CGI script, which it can't since it gets input from a socket instead of stdin and has a never-ending loop. What you need is a wrapper that switches the user id and then executes your script for safety. Just a line in rc.local like "su -c tornadoID "/home/matt/tornadoServer/tornadoDeploy.py &" where tornadoID is a restricted user id under which you will run your server. – Allen Dec 26 '10 at 23:35
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up vote 1 down vote

The Ubuntu (and Debian) way to get applications to start at boot time is to turn them into system services using update-rc.d -- see here for instructions: http://www.debuntu.org/how-to-manage-services-with-update-rc.d

Remember that anything that runs as root is a potential security vulnerability, especially if other users can modify it.

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If you run it from rc.local, you also need to edit /etc/sudoers and comment this string:

Defaults requiretty

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