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SubjectRe: Building Big Ass Linux Machine, what are the limits?
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Stephen C. Tweedie wrote:
> Hi,
>
> On Thu, 1 Oct 1998 09:59:45 +0200 (MEST), R.E.Wolff@BitWizard.nl
> (Rogier Wolff) said:
>
> > I've been thinking about this "change disk now" questions that the
> > kernel might need to ask.
>
> > I thought I'd make a character device that simply outputs the question
> > to be posed to the user.

> I'd love to know how this is supposed to work on a multi-user system
> that has users logging in from a dozen different modems and X
> terminals at the same time!

My thought was that if you access the device, you should run the
application that shows you the message. If you're accessing the
multivolume device and forget to run the application, you're on your
own.

The person at the console is the one that most likely has physical
access to the devices in question, so running the reporting program
would for the "change disks" message be most appropriate for those
sitting at the console.

But if it's say a departemental server, all of the X sessions might
want to include the "get messages program", allowing the person that's
working on the volume to step up and walk over to the server to change
disks.

> The kernel disk quota system also needs to be able to notify the current
> user when quota is exceeded, and currently (in common with other Unixen)
> we just output the message to the process's controlling tty device.
> You'd need much more than just a single character device to deal with
> this in any significantly better way.

How about adding the uid of the user doing the access to the messages
given through the character device. A sysop would run

report_messages -all /dev/messages

and get all "over-quota" and "please insert disk" messages. A user
that doesn't want to be spammed by others doing stuff would do:

report_messages /dev/messages

to only get HIS OWN messages. (filtering outside of the kernel).

Roger.

--
| Most people would die sooner than think.... | R.E.Wolff@BitWizard.nl
| in fact, most do. -- Bertrand Russsell | phone: +31-15-2137555
We write Linux device drivers for any device you may have! fax: ..-2138217

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