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Linus smoking crackLinus smoking crackPosted Jan 9, 2004 0:21 UTC (Fri) by Ross (subscriber, #4065)Parent article: The future of device numbers Randomized numbers?! Anything that depends on them broken?! Linus likes to shock people too much. But taking him literally, just about everything is broken. My /dev directory isn't going to magically update itself by somehow guessing the proper major nad minor numbers for each device. And NFS exports of devices will do "interesting" things... randomly different on each client. I'd have to boot my system hundreds of thousands of times before getting lucky enough to get the correct mapping. So I don't see this happening until something like udev and a static mapping layer for things like NFS. And since udev is on hold and devfs is a piece of junk... I'll continue to use my static mapping and it better keep working or I'm just not going to use 2.6.
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Linus smoking crack Posted Jan 9, 2004 6:53 UTC (Fri) by AdHoc (subscriber, #1115) [Link] I think Linus means to put the randomization into the 2.7 (unstable dev) tree when it is released, then remove it when the 2.8 (stable) tree is released.
Linus smoking crack Posted Jan 9, 2004 8:45 UTC (Fri) by iabervon (subscriber, #722) [Link] Linus is actually talking about randomization of the devices that thekernel can't necessarily keep stable. So it's only really hotpluggable devices, disks that can show up in surprising places, and that sort of thing. I doubt /dev/zero will be change around between boots (which would potentially cause problems with memory allocation in udev necessary to create a device node with the right number...), and IDE disks and floppies will probably stay the same. TTYs, PTYs, and so forth might as well stay the same, since they're mostly kernel constructs anyway. What'll be different is things like SCSI disks (which includes USB storage), which will probably get random numbers instead of getting numbered sequentially by when they're detected; if you're depending on those being static, you could be in for an unpleasant surprise if you boot a SCSI machine with a USB camera plugged in (even today, maybe). The point is that the kernel can't necessarily identify the same device is you unplug it and replug it, or if you reboot with different hardware attached than you did last time. There are some cases where it is reliable, and some cases where hardware doesn't matter, but there are other cases where it can't do it reliably; in this case, it's far better to fail the first time than wait to fail until it really matters.
No he really means ALL device numbers Posted Jan 10, 2004 4:58 UTC (Sat) by giraffedata (subscriber, #1954) [Link] Linus is actually talking about randomization of the devices that the kernel can't necessarily keep stable.That's exactly what he's not talking about. Linus says that the fact that the kernel can't provide stable device numbers for everything means that anyone who expects the kernel to provide static device numbers for anything is fooling himself. Therefore, he suggests making device numbers random even when they don't have to be so someone can't possibly think that device numbers are stable. He backpedals a little and says that might be a little too hostile and out of practicality, some device numbers should be kept unrandom. But what he really believes is that all the device numbers should be random. This whole thing assumes udev, of course. If you have static device special files in /dev that you created with mknod, as we have for 30 years, you obviously can't make all the device numbers random. I wish we'd get away from device numbers altogether. Naming things with integers is really archaic. In the modern world, we either name them with long text strings or with temporary handles that have reference counts and are in reality memory addresses.
Linus smoking crack Posted Jan 15, 2004 18:10 UTC (Thu) by zdzichu (subscriber, #17118) [Link] Well, it seems that 2.7 will be almost unusable without udev or devfs.
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