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Re: debian and UDEV

Am Freitag, 19. Mai 2006 03:14 schrieb Goswin von Brederlow:
> Hendrik Sattler <debian@hendrik-sattler.de> writes:
> > Am Donnerstag, 18. Mai 2006 21:53 schrieb Goswin von Brederlow:
> >> But how do you detect when there is no device to be found to call the
> >> function?
> >
> > That's of absolutely no interest because in this case, you cannot go on,
> > having synchronous events or not. However, you might have alternatives
> > for a root partition that are fulfilled with another function call.
> > The point is that to keep the goal in mind: you want to achieve something
> > e.g. by probing many different possibilities.
> > Lets say you want to find a scanner: you probe SCSI busses, spawn a
> > thread that test the parallel bus and another one for USB and whatever
> > else. You only want to find one. You don't synchronize on any of those
> > specific events but on the result: that a scanner is found.
> > Sure, you need a timeout, but it is unrelated to a specific probing
> > method
> So you mean you register a function for "block device found" and then
> scan all the ide, sata, scsi, usb, ... drivers from the initrd and for
> every disk and partition the function gets called. When it gets called
> with the partition with the right signature (label or uuid for
> example) it mounts / and continues.
> Not a function for "scsi disk ID 0 on scsi0 (3ware) found".
> I see what you mean. Keeping the function abstract enough allows
> removing a disk and plug it in somewhere else, e.g. change the scsi
> ID.

Almost. It can still be "scsi disk ID 0 on scsi0 (3ware) found" but that it a 
matter of only the script to mount root and /etc/fstab (which also allows for 
LABEL and UUID, as alternative to the links in /dev created by udev), not the 
other script that wants root mounted and waits until this is the case.

However, I am not sure that this is really done this way, currently. Would be 
the cleanest approach, though.


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