mknod bug? major minor's are whacky

mknod bug? major minor's are whacky

[Bob Goldberg]

cygwin 1.7.6

attempting to:
$ mknod null c 1 3

what I get is:
crw-rw-rw- 1 user mkgroup-l-d 46200, 14467 2010-08-17 18:44 null

WHERE did those crazy major/minor's come from!?!?

and how do I re-create a null device if mknod doesn't work right?
TIA

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Re: mknod bug? major minor's are whacky

[Eric Blake]

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On 08/17/2010 05:46 PM, Bob Goldberg wrote:
> cygwin 1.7.6
> 
> attempting to:
> $ mknod null c 1 3
> 
> what I get is:
> crw-rw-rw- 1 user mkgroup-l-d 46200, 14467 2010-08-17 18:44 null
> 
> WHERE did those crazy major/minor's come from!?!?

The fact that your owner is mkgroup-l-d is probably a hint - my guess is
that cygwin is returning -1 because you haven't set up your user
database correctly, rather than an actual device number.  If that's the
case, then cygwin could probably be fixed (device major/minor node
numbers need not depend on whether the user database is set up correctly).

At any rate, Cygwin does not necessarily use the same major/minor node
numbers as Linux.  Any use of mknod outside of creating named pipes is
_highly_ platform dependent, and your best bet is to read the source
code for the actual node numbers that cygwin supports rather than
relying on something that worked for Linux.

-- 
Eric Blake   eblake@redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org


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Re: mknod bug? major minor's are whacky

[Corinna Vinschen]

On Aug 17 17:51, Eric Blake wrote:
> On 08/17/2010 05:46 PM, Bob Goldberg wrote:
> > cygwin 1.7.6
> > 
> > attempting to:
> > $ mknod null c 1 3
> > 
> > what I get is:
> > crw-rw-rw- 1 user mkgroup-l-d 46200, 14467 2010-08-17 18:44 null
> > 
> > WHERE did those crazy major/minor's come from!?!?

They come from Cygwin.  They are an accidental reflection of the
volume id, which is used in stat::st_rdev for files by default.
Cygwin only set st_dev to the device number so far.  I fixed that
in CVS so that st_rdev and st_dev both contain the device number
now for device files.


Thanks for the report,
Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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