problem mounting DVD

dgitelman · 03-02-2004, 07:25 PM

I am running redhat 8.0. I have a Teac combo drive (DV-W58E) installed.
It is CD read/write and DVD+R/RW read/write. If I put a CD in the drive it
mounts fine and I can see its contents under /mnt/cdrom. If I put a DVD+R
in the drive I can mount it, but when I type ls /mnt/cdrom it lists the contents
of /mnt/cdrom and then says permission denied. However, as root I can see
the DVD just fine. I can also burn CD's in the drive using xcdroast, but if I put
in an blank DVD it appears not to recognize it as a dvd and the xcdroast says
there is a blank CD in the drive. (I have installed the key for xcdroast, by the way,
and the appropriate binaries, so the buttons do say burn cd/dvd.

If I change my /etc/fstab to say the file system is iso9660 instead of auto
(see below) then the dvd mounts just fine with no permission problems, but
of course the filenames are abbreviated.

I know the drive is working fine because I took it out, installed it in a windows
machine and it recognized and burned a dvd just fine.

Here is some system info:

/etc/grub.conf contains the line
kernel /vmlinuz-2.4.18-14 ro root=LABEL=/ hdc=ide-scsi

/etc/fstab contains the line
/dev/cdrom /mnt/cdrom auto noauto,user,kudzu,ro 0 0

ll /dev/cdrom
lrwxrwxrwx 1 root root 9 Mar 2 18:59 /dev/cdrom -> /dev/scd0

ll /mnt
drwxr-xr-x 2 root root 4096 Mar 2 18:59 cdrom

I've run out of things to try. Any suggestions,
Thanks,
Darren

Tinkster · 03-03-2004, 01:10 AM

Quote:

Originally posted by dgitelman
ll /dev/cdrom
lrwxrwxrwx 1 root root 9 Mar 2 18:59 /dev/cdrom -> /dev/scd0

So ... what are the permissions on the
original device, rather than the links?

ll /dev/scd0

?

Cheers,
Tink

dgitelman · 03-03-2004, 09:44 AM

Thanks:
The original permissions were
brw-rw-rw- 1 root disk 11, 0 Aug 30 2002 scd0

So I tried chmod 777 scd0, but that didn't help.

I looked at the directory I'm mounting the drive to. When there is no cd/dvd mounted the permissions say
drwxrwxrwx 2 root root 4096 Mar 2 18:59 cdrom

When I mount a cdrom (mount /dev/cdrom) the permissions become
dr-xr-xr-x 3 root root 2048 Jul 10 2003 cdrom
and of course I can read the data, no problem.

However, when I instead mount a dvd (mount /dev/dvd) the permissions become
dr--r--r-- 2 4294967295 4294967295 132 Mar 3 00:00 cdrom

I added dvd to /etc/fstab by the way, so that I now have these entries.
/dev/cdrom /mnt/cdrom auto noauto,users,exec,kudzu,ro 0 0
/dev/dvd /mnt/cdrom auto noauto,users,exec,kudzu,ro 0 0

That same weird uid and gid is seen for every dvd that is mounted- some burned on windows machines and some burned on linux machines. However, root has no trouble seeing the data on the dvds so I know the filesystems are good, but not regular users. I am mounting data dvd's by the way not commercial dvds.

I also tried adding myself to the group disks, but that didn't help.

darren

Tinkster · 03-03-2004, 03:27 PM

Sorry, no idea what to do ... the kudzu bit in
the mount-options and the "change permissions
on the fly" must be specific to Little Red Ridinghood's
way of doing things...

Cheers,
Tink

dgitelman · 03-03-2004, 06:11 PM

I took out the kudzu thing, no improvement.
If I had to boil this down to one issue then if I mount the dvd as type iso9660 then all is good and both users and root can read it. However, if I mount it as udf then only root can read it. Why is this? I can find nothing on why mounting with different fs type would change the permissions on the mount.

Tinkster · 03-04-2004, 12:09 PM

As I pointed out earlier ... I've never heard of the
like before, but then I don't have to deal with little
Red Ridinghood, either :}

Sorry.

Cheers,
Tink

ptahlis · 07-20-2004, 02:40 PM

I am experiencing the exact same problem on a Fedora Core 2 system. Root can read the drive just fine, but no users can. I posted at FedoraForum .org yesterday:

Quote:

I'm having some problems with mounting data DVDs created on a Windows machine. Although I'm a newbie, I have tried man mount, man fstab, and searching these forums for clues as to what I'm doing wrong, but haven't been able to figure it out.

Here's what's going on:

I have a laptop with a combo CD-RW/DVD+RW drive. Any CD I've tried to use so far has worked fine. I haven't tried DVD video yet. DVD data (read) works fine, but only if I am trying to access it as root. If I try as my normal user I get the following error: bash: cd: /mnt/cdrom: Permission denied

Here's the relevant line from my fstab file:

/dev/cdrom /mnt/cdrom udf,iso9660 noauto,users,kudzu,ro 0 0

Before I mount the drive the /mnt/cdrom permissions are:
dr--r--r-- 36 hansenc hansenc 3908 Jul 16 13:58 cdrom

and after mounting they are:
dr--r--r-- 36 4294967295 4294967295 3908 Jul 16 13:58 cdrom

Things I have tried:

After mounting the drive I have tried changing the permissions via chmod, but I get an error message because the filesystem is read only. If I remove the "ro 0 0" from fstab I can mount the drive (with an error message that basically states the device will be mounted read-only) and also successfully browse it as a user. BUT the long filename support (Rock Ridge/Joliet?)is no longer there, and I can't do without that. Permissions after such a mount operation look like this:

dr-xr-xr-x 1 root root 2048 Jul 16 07:58 cdrom

I have tried modifying the fstab entry by removing kudzu, and by inserting a uid= and gid= statement without achieving any success at all. In the end, I can use the DVD as I need to only as root. As a user I either get "permission denied" or I have to use 8.3 format filenames. I would appreciate any insight someone can offer as to how to fix this, and just as importantly (because I do want to learn) why it's acting this way in the first place.

Thanks,

ptahlis

Additional Info: I have also tried a couple things not mentioned above. Changing permissions (and owner) on hdc, where /dev/cdrom links to, did not help, nor did using 'owner' in place of 'users' in fstab make any difference.

Hopefully some fresh eyes will see this and someone will figure out what the problem might be, 'cause I am totally stumped.

bad_gui · 09-07-2004, 02:10 PM

I have a dvd written on a Windows XP machine by someone else (I don't
know how it was written) that I can only access as root even though the
permissions for the drive and mount point are univeral read. I can mount it
as iso9660 and read it as user but the filenames get truncated.

Could it be that the UDF permissions on the disk override the mount and device settings?

http://www.uemforums.com/2pop/ubbthreads/showflat.php?Cat=&Number=3632&page=4&view=collapsed&sb=11&o=&fpart=1

Quote:

he following is a "UDF For Dummies" summary which may be more understandable:

• The primary volume descriptor (also known as UDF) is set up at authoring. This is part of the user data that Synchronicity cannot alter in the mastering process.
• The error "UDF File/Dir Permissions Incompatible with Read-Only Media" indicates that the permissions set at authoring allow for file and directory changes or deletion. The bottom line is that the replicated DVD disc from input media with this permission incompatibility may get characterized by the DVD drive as a DVD-R rather than read-only. (Note that all DVD drives have an initialization sequence that they go through to define the type of disc in the drive. This sequence is part of the firmware created by the drive manufacturer. There is no industry specification for this initialization sequence. As such, a drive manufacturer creates this initialization sequence as they see appropriate and the sequence varies based on the original equipment manufacturer.)
• If the disc is incorrectly described as a DVD-R after this initialization sequence and if the drive is not designed to play DVD-R discs, it may reject the disc.