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When trying to burn a DVD it sometimes happens that growisofs will fail with:

$ sudo growisofs -speed=8 -dvd-compat  -Z /dev/scd0 -J -r .
Executing 'genisoimage -J -r . | builtin_dd of=/dev/scd0 obs=32k seek=0'
I: -input-charset not specified, using utf-8 (detected in locale settings)
0.23% done, estimate finish Fri Sep 16 14:49:33 2011
0.46% done, estimate finish Fri Sep 16 14:49:33 2011
0.69% done, estimate finish Fri Sep 16 14:49:33 2011
:-( unable to O_EXCL /dev/scd0: someone was in time to remount?

This only seems to happens when burning multiple DVD's in a row and I think it happens when I eject an automounted disc without manually unmounting it first, which implies that something is keeping the drive busy, lsof and fuser however fail to find a process still accessing the drive. Rebooting makes the problem go away.

How can I find out what process is causing this issue?

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This can happen if your /etc/fstab has the following line for your cdrom:

/dev/cdrom /media/cdrom auto rw,noauto,user,exec 0 0

Change it to

/dev/cdrom /media/cdrom iso9660 rw,noauto,user,exec 0 0

, reboot and try if it still happens.


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up vote 0 down vote accepted

I have been running into issue now again a few times and I am reasonably confident that it is really nothing more then having an shell open that is still in /cdrom/ and thus prevents a proper unmounting of the drive.

Still no idea on how to find the trouble causing shell with lsof or fuser, but there is another way that should work:

sudo ls -l /proc/*/cwd  | grep -i cdrom
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had this issue too, with 12.04 LTS, default desktop GUI setup (running from the livecd on a USB stick, actually). Hit the eject button on the drive to umount and open the tray,but now growisofs can't open /dev/sr0 with O_EXCL. I guess it didn't really unmount? But there's nothing about it still in /proc/mounts, and no processes with a cwd in /media or anything. I can mount and unmount burned discs with no complaints or effects on the problem. Is there a bug open for this on Launchpad? – Peter Cordes Dec 27 '12 at 5:01
update: actually some mounting and careful unmounting do appear to have solved it. /proc/<pid>/cwd doesn't show the working directory of a process still CDed to a force-unmounted filesystem, so I did find a shell that might have been CDed to a CD while I was trying to burn the first time – Peter Cordes Dec 27 '12 at 5:13

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