CDROM autoload on commandline

jazernorth · 05-27-2004, 01:13 PM

The Plan:
I am setting up a self-sustaining Linux system that requires no user interaction on the terminal. Once booted, and not logged in, if a CDROM is loaded into the drive I want the system to launch a desired application.

The Question:
How do I receive signals from the kernel/system that a CDROM is loaded?
How do I determine whay type of CD it is (ie Audio or data)?

Any help would be greatly appreciated.

JN

Vlad-A · 05-27-2004, 03:27 PM

So no one is logged in. My question: In which user context shall the action be executed when the CD-ROM is inserted?
Root ? Normal user ? I mean this can be a serious treat to the overall syste security.

I think that you have to write a daemnon, which is then started on system start-up/boot.

This deamon can check if a CD-ROM is inserted or not.

One option can be by:

...
while ( (handler=open("/dev/cdrom", O_READONLY)) == -1)
sched_yield();
...

with ioctl you can detremine what type the cd is.

I *suggest* you take a look in file:/usr/src/linux/drivers/cdrom directory and browse through
the sources of the cd-rom subsystem for further information.

You may also take a look on the supermounter (submount) sorces to get an idea
how to write an autodetect for cd-rom insert.
http://sourceforge.net/projects/submount/

You may also consider to browse the web to see if maybe someone has already written
such software.

jazernorth · 05-28-2004, 06:23 AM

I already have automounter installed and working fine. I have to enter the /auto/cdrom folder (location where I put the automounter mount) to activate the cdrom. I know there is a way to mount and load the cd when it is inserted into the drive. My Red Hat system does this when I am in X, using KDE. I would like the same feature when I am at the command line (not in X at all).

As for the user, the system is standalone in a place where security doesn't really matter. Plus I am hoping that when I catch the insert cdrom signal that I can have it execute a job as a dummy user.

So, in short, I need to know how to start an application when a signal is sent from the cdrom. I will use the application to mount the cdrom.

I couldn't get the while code posted earlier to work. Maybe I need a little more instruction on what it is supposed to do and where it is supposed to be put.

Thanks.

Jay

Vlad-A · 05-28-2004, 06:58 AM

It could look like:

#include <unistd.h>
#include <fcntl.h>
#include <sched.h>

int main ()
{
int handler;
while ( (handler=open("/dev/cdrom", O_READONLY)) == -1) sched_yield();

###### CD-ROM inserted #########
close handler;
##### YOUR ACTION ######

return (0);
}

now compile it using gcc.

You may start it via an init script in the run-level you want. init level 3 is one where you do not have X.

/dev/cdrom is the device file for your CD-ROM. You may use a different name according to the
dev file of your CD-ROM.

BTW: You may try to mount a CD. If mount succeeds then it's very likely that you have a data CD.
If NOT, then either there is a Audio CD inserted *or* something's wrong with the CD media.
So the mount test isn't 100% bullet proof., but it's simple to implement.

jazernorth · 05-28-2004, 10:14 AM

What I ended up doing:
Already had autofs installed (uses automounter, except it is used on distros other than debian and redhat).
installed cdde (compact disc detection and execution) available at http://freshmeat.net/cdde
had to write a python script to launch cdde in daemon mode:

Code:

#!/usr/bin/python
import os
pid = file('/var/run/cdde.pid','w')
pgm = 'cdde'
arg = [pgm,'-c','/etc/cdde.xml']
this = os.spawnvp(os.P_NOWAIT,pgm,arg)
pid.write(str(this) + '\n')
pid.close()

Created init.d script:

Code:

#!/bin/bash
# Begin $rc_base/init.d/cdde

source /etc/sysconfig/rc
source $rc_functions

case "$1" in
     start)
          echo "Starting cdde..."
          loadproc /usr/sbin/cdde_py
          ;;
     stop)
          echo "Stopping cdde..."
          killproc /var/bin/cdde
          ;;
     reload)
          echo "Reloading cdde..."
          killall -HUP cdde
          ;;
     restart)
          $0 stop
          sleep 1
          $0 start
          ;;
     status)
          statusproc /usr/bin/cdde
          ;;
     *)
          echo "Usage: $0 {start|stop|reload|restart|status}"
          exit 1
          ;;
esac
# End $rc_base/init.d/cdde

Then I make the init.d script execute on boot up using:

Code:

cd /etc/rc.d/init.d &&
ln -sf ../init.d/cdde ../rc0.d/K25cdde &&
ln -sf ../init.d/cdde ../rc1.d/K25cdde &&
ln -sf ../init.d/cdde ../rc2.d/K25cdde &&
ln -sf ../init.d/cdde ../rc3.d/S35cdde &&
ln -sf ../init.d/cdde ../rc4.d/S35cdde &&
ln -sf ../init.d/cdde ../rc5.d/S35cdde &&
ln -sf ../init.d/cdde ../rc6.d/K25cdde

I modified the /etc/cdde.xml according to the cdde instructions.

Now when I insert a cd, no matter the type, it will launch the desired application accordingly.

Works pretty much how I wanted.
[edit]Small clarification: I use as the command /auto/cdrom, when it is a data cd to get the drive mounted. Then all I do is use the information from it.
If it is an audio cd, I launch an application that rips the cd to mp3's and ejects the cd when complete.
[/edit]

Thanks for all of the pointers. I wouldn't have known where to look for any of the iformation without certian key words.

JN