Re: /dev/cdrom is not a valid block device

From: Jan Minar (Jan.Minar_at_seznam.cz)
Date: 01/05/04

  • Next message: Jan Minar: "Re: /dev/cdrom is not a valid block device" 
    Date: Mon, 5 Jan 2004 10:21:23 +0100
To: debian-user@lists.debian.org

    Hi, Stephen.

    On Mon, Jan 05, 2004 at 04:51:06AM +0800, Stephen Liu wrote:
    > $ eject /mnt/cdrom or
    > $ eject /mnt/cdwriter
    > did not work.

    Ejecting the device is done by ioctl(2)-ing the device, i.e. writing to
    it:

    | (#:/usr/src/linux-2.4.23)- sudo -u toor eject
    | eject: unable to find or open device for: `cdrom'

    --where `toor' is an unprivileged user.

    You must have a write access to the device to accomplish this. The
    Debian way is, as was already pointed out by David Goodenough:

    > > > Add yourself to the cdrecording group, (or whichever group /dev/hdc is
    > > > owned by).

    -- You didn't do your homework, did you :-(

    If you are worried by the problems of the group-driven security, create a
    new group for the /dev/cdrom device, or use sudo. If the limitations of
    the Unix security model are unbearable, you might consider using kernel
    patches allowing more fine-grained security control, e.g. RSBAC. Maybe
    the new security framework of the 2.6 line will do something for you,
    too.

    In my case, for example, all the cdrom drives are owned by root.cdrom
    % ls -l /dev | grep cdrom | grep hdc
    lrwxrwxrwx 1 root root 3 Dec 10 03:45 cdrom -> hdc
    brw-rw---- 1 root cdrom 22, 0 Mar 14 2002 hdc
    % grep cdrom /etc/group
    cdrom:x:24:jan

    The `user' or `users' option in /etc/fstab will allow the user to
    _mount_ the _filesystem_, not read/write the raw device. man mount for
    details.

    Please make sure to understand the advises before reporting further
    problems the next time :-(

    HTH. 

    -- 
Jan Minar                   "Please don't CC me, I'm subscribed." x 7



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