Messages in this thread | | | Date | Fri, 18 Jun 1999 15:14:11 +1000 | From | Richard Gooch <> | Subject | Re: UUIDs (and devfs and major/minor numbers) |
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tytso@mit.edu writes: > Explain to me how this is different from mounting devfs onto /kernel > and using devfsd to populate a disc-based /dev. > > It isn't, as long as the names given by devfs are specific enough that a > user-mode daemon knows what the device is. So if devfs is creating > names like sda1, or c0t0d0s4, this isn't useful. Names like: > /kernel/devices/pci/adapecc2980_0/... aren't something you'd *want* to > appear in /dev, and indeed they don't appear in /dev under Solaris.
I don't see how a hardware-based name like /kernel/devices/pci/adapecc2980_0/... is any better than one that includes the host#, bus# and so on.
> But this is a straw-man argument, because it ignores the persistence > problem with a dynamic disc-based /dev which is managed with a user > space daemon. This is a problem that's been overlooked. > > Consider what happens if your daemon creates and deletes device > entries based on information from the kernel as to what devices are > installed (and drivers loaded). When a new device is plugged in, *what > permissions should be given*? OK, say you get some default. So the > sysadmin does chmod(1) to change this. > > What happens if a device is removed? The daemon deletes the device > entry. Then the device is plugged back in again. *What permissions > will be given*? > > What makes you think the daemon should delete the device entry? I > wouldn't. I would keep it there, since the device entry is cheap, > and most of the time when a device is removed it's likely to come > back later. In the rare case where hardware is being physically > removed and it will never come back, the system administrator can > simply delete the device for good later.
I'd want it removed, since it's clutter if there hardware isn't there.
> Again I'll ask the question I've already asked a number of times. How > would you cleanly support a construct like this: > opendir ("/dev/ide/cd"); > loop; > > 1) I don't think this is useful.
Yes it is.
Regards,
Richard....
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