Re: How to coordinate a DVD burn program with udev ?
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Hi, Tom Gundersen wrote: > Could you possibly use one of the /dev/disk/by-* links instead? As far > as I understand, the rule generator is being deprecated. Aside from the general problem, i can of course advise my users to use whatever is reliably existent and can be unambigously documented. The files in /dev/disk/by-id seem not to represent any of the two DVD drives. In /dev/disk/by-path i see them as /dev/disk/by-path/pci-0000:00:11.0-scsi-2:0:0:0 /dev/disk/by-path/pci-0000:00:14.1-scsi-0:0:0:0 But i understand that these addresses are prone to change at boot time, too. And they would uglify any program message that contains a drive address. Alternatively one can find the desired /dev/sr address by running xorriso -devices I could even implement in libburn a functionality similar to udev which identifies drives by unique persistent properties. But that would not prevent other problems which can arise from udev trying to inspect the busy CD drive. > Sorry to not answer your main question, I'm not sure exactly what is > happening... Maybe someone else can shed some light on it? The vanishing links are only one example symptom of the general problem that udev tries to perform SCSI commands on a CD drive that is already aquired with open(O_EXCL) and might be brought into a state which does not tolerate such interference. Especially with media types CD-R, CD-RW and DVD-R this often results in misburns. Obviously there are race conditions deciding over success or failure of the coexistence of udev and burn program. xorriso is hit more than the others, because it inspects the media content additionally to the drive's MMC properties. Nevertheless i can reproduce the problem with wodim. It is a general one. libburn and xorriso are part of a project that tries to improve the neighborhood relations between Linux and burn programs. Different to growisofs and wodim it is under maintenance (by me), and different to the author of cdrecord i am willing to follow instructions from the Linux developers. But first i need to get such instructions when Linux changes its behavior. The random permutation of /dev/sr addresses at boot time is such a change. I understand the recommended way to cope with this device juggling is to use the udev links. Now what shall a user think of udev and/or xorriso if this recommended solution goes up in smoke on first use ? Is there a better place than this mailing list where i could ask for advise ? Especially i wonder what the designers of kernel and udev have planned for the use case of CD/DVD/BD burning. Have a nice day :) Thomas -- To unsubscribe from this list: send the line "unsubscribe linux-hotplug" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html