#1912: Possible bad interaction of udev rules for duplicate devices
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Reporter: [EMAIL PROTECTED] | Owner: Bryan Kadzban
Type: defect | Status: new
Priority: normal | Milestone: 6.3
Component: Book | Version: SVN
Severity: normal | Resolution:
Keywords: |
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Comment (by Bryan Kadzban):
Replying to [comment:9 [EMAIL PROTECTED]:
> Actually, I remember a discussion some time ago about a proposal to have
the kernel probe devices in parallel during bootup. If that happens, I'm
not sure that by-path persistence will be suitable for anything, right?
Not exactly, I don't think. Parallel device probing is done in 2.6.19 and
above, in any case.
But I don't think the numbers in the by-path IDs match the order that the
devices were discovered in. I think they're supposed to match bus/slot
numbers (for PCI) or bus/port numbers (for USB). I've just tested this
(somewhat) by plugging a USB flash device into the same USB port twice --
in both cases, the /dev/disk/by-path symlinks were the same. But when I
plugged it in somewhere else, the symlinks were different.
> So, let's not bother patching Udev, we'll describe by-path and by-id for
CD drives. We'll describe by-mac for network interfaces.
Sounds good to me; I'll try to do it in the next couple days. :-)
Replying to [comment:10 [EMAIL PROTECTED]:
> Wouldn't the same issue arise on a USB cdrom drive, for example?
Yes it would, see the USB flash device example above. Plugging it into
another port made the path ID change; I don't see how a CD drive would act
any differently.
There '''may''' be fewer people with USB CDs than USB NICs, but I really
have no idea.
I do think it makes sense to keep by-path for CDs, though, just because
that was the only option up until udev-104. It was what Debian originally
released (with no other option), so having our system act like another
system that the user has a decent chance of already knowing is probably
not bad. Also, leaving it in provides a halfway-decent place to put the
warning about path persistence on hotpluggable buses.
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Ticket URL: <http://wiki.linuxfromscratch.org/lfs/ticket/1912#comment:11>
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