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GNU/Linux Desktop Survival Guide
by Graham Williams


One likely cause of your CD/DVD not being found is that the appropriate module has not bee loaded. Try loading ide-scsi to see if that helps!

  # modprobe ide-scsi

If that works you may want to add ide-scsi to /etc/modules so it will be loaded on reboot.

Otherwise, to make use of a CD-ROM device you need to know what device it is mapped to. Let's assume it is /dev/hde (but look through the output of the dmesg command to see which it is). If the device /dev/hde does not exist (for modern versions of Debian it usually does exist as the devices where identified at boot) you will need to create it with MAKEDEV as root:

  # cd /dev
  # ./MAKEDEV hde

As a common convenience /dev/cdrom points to the physical device /dev/hde using a symbolic link:

 # ln -s /dev/hde cdrom

You can then mount any data CD-ROM:

  # mount /dev/cdrom /media/cdrom
  # ... 
  # umount /media/cdrom

If users can not mount the CD-ROM device then they probably don't have the right permissions. To allow general access to the CD-ROM edit /etc/fstab to add the following line.

  /dev/cdrom  /media/cdrom  auto  defaults,noauto,users,ro,nohide  0 0

Any user can then mount and unmount /media/cdrom, irrespective of who mounted it. Also note that the standard CD-ROM format is iso9660 and the auto in the above could have been this. However, as DVDs become more common using auto allows the udf format to also be recognised with no extra effort.

The Gnome mount applets allow a user to mount and unmount the CD-ROM. Make sure you unmount the CD-ROM before you physically remove the media. (For most drives the eject button is disabled while the CD is mounted.)

The various options in the /etc/fstab line above are: ro which mounts the file system as read-only; users which lets all users mount and unmount the file-system; noauto which means that the file-system is not automatically mounted at boot time; and nohide which shows hidden and associated files.

With the above entry in /etc/fstab the command line mounting of the partition becomes:

  # mount /media/cdrom

By default the CD-ROM device belongs to group disk. For audio CD access the user will need to be a member of the group to which the device belongs. But do not add users to the group disk because this will give them read/write access to raw devices for all disks meaning that they can directly read the bits off the hard disk and effectively ignore file system permissions. Instead change the Unix group of /dev/hde from disk to cdrom and add users who need access to the drive to the group cdrom:

  # chgrp cdrom /dev/hde
  # adduser kayon cdrom

Next time user kayon logs on they will be in group cdrom in addition to the other groups they were already in. They will then have access to the CD-ROM device.


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