Ah Linux, where there's usually an answer, but it's different for everyone. Maybe I can get you started. Ubuntu 12.10 picked up an upstream change that automounts media in a directory that changes by user ID. (Justification for the change can be found at freedesktop.org.) You want a static location shared by all users.
The quick and dirty fix is to symlink all your users' mount points back up to the shared directory, something like
sudo ln -s /media/$USER/* /media/. See How to configure the default automount location? Note a comment by rocko in that reference claiming a better, general solution is coming in Ubuntu 13.04.
In 12.10 a solution better than the symlink hack is to arrange a static mount point in /etc/fstab. In my case, I have a USB CDROM drive, and this works as far as I've tested it:
- Find the symlink for the CDROM device in udev rules:
in my case, there was a series of entries for my PLDS_DVD device including one with SYMLINK+="cdrom", meaning the device shows up at /dev/cdrom.
- Create a suitable static mount point:
sudo mkdir -p /mnt/cdrom
- Link these things together in /etc/fstab with a line like this:
/dev/cdrom /mnt/cdrom iso9660 ro,user,noauto,unhide
- Create a Samba share using
path=/mnt/cdrom (you know how to do this already)
I'm just piecing things together here, and honestly I haven't tested this whole series in exactly this way, but you should be able to share the CD after some user, any user, manually mounts: