communication between UDEV and HALD

[John Tapsell]

2008/9/24 Matthew Garrett <mjg59 at srcf.ucam.org>:
> On Wed, Sep 24, 2008 at 08:07:33PM +0530, Girish Hilage wrote:
>>
>> >You mean your manual umount/mount events or what? If you don't do automatic
>> > mount handling you can't IMO see anything, since then nobody mount/umount.
>>
>> No. I mean when I insert a new CD in CD drive and when I remove the CD from CD drive by pressing 'eject', then I could not see 'mount/umount' events respectively.
>
> If you stop hal, then whatever is automounting your CDs will be unable
> to mount your CDs. As a result, you won't see the mount/umount events.


Girish,

  Reading between the lines of Garrett is saying, I think what happens
is that Hal basically detects the event of a new CD being entered and
runs a script to mount the CD.  The program 'mount' is called, and
this tells the kernel to mount the drive.  The kernel does so and
updates /proc/mtab.   Udev now sees that /proc/mtab has changed, scans
it, and realises that the CD has been mounted.  Udev does emits a
mount event.

I've probably got the details wrong, but that's what I've gathered so far.

John


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