K3b needs some special permissions to work properly. Most distrobutions come with permissions that I don't like
very much and make problems when adding new CD/DVD devices to your system.
If you set up your system as follows you can be sure to never have K3b permission problems again.

1. Disable pam authentication for cdrom and burner devices in /etc/security/console.perm. Otherwise your permissions
   will be overwritten when loggin in and it's not possible for two users to use K3b at the same time.
   In my opinion one should disable this completely and create a proper configuration instead. The most annoying
   issue with this pam stuff is that you cannot have two sessions with two different users running because the first 
   one owns all the sound and cd devices.

2. Create a cdrom or cdrw or whatever group (if it not already exists) and add all users that should be able to
   use K3b to that group. You may also skip this step and let everybody use K3b. In that case simply use root as
   the group and permissions 4711 and 666 instead of 4710 and 660 in the following steps.

3. Change the permissions of cdrecord and cdrdao to 4710 root.cdrom (substitute cdrom with the group from 2).
   This way both will run suid root which allows them to increase their scheduling priority resulting in a more
   stable burning process.

4. Change the permissions of all your cdrom device to 660 root.cdrom (substitute cdrom with the group from 2).
   With devfs you may do this with lines like this (the first changes all ide cd devices while the second takes
   care of the scsi cd devices):
     REGISTER        ^ide/host.*/bus.*/target.*/lun.*/cd          PERMISSIONS root.cdrom 660
     REGISTER        ^scsi/host.*/bus.*/target.*/lun.*/cd         PERMISSIONS root.cdrom 660
   In case you are not using devfs you may determine the devices by running K3b once as root and looking in the
   device settings. The corresponding devices are listed there.

5. Change the permissions of the generic SCSI devices to 660 root.cdrom (substitute cdrom with the group from 2).
   Both cdrecord and cdrdao use the generic devices to access the scsi drives. So you don't need to perform this step
   if you only have IDE devices.
   Use a line like the following for devfs:
     REGISTER        ^scsi/host.*/bus.*/target.*/lun.*/generic    PERMISSIONS root.cdrom 660
  In case you are not using devfs the devices are /dev/sg*.
