[Udpcast] poweroff not doing the job

Alain Knaff alain at knaff.lu
Tue Jul 20 11:51:09 CEST 2004


On Thursday 15 July 2004 17:14, Donald Teed wrote:
> There is no shutdown command in busybox.  I don't know if
> a statically compiled one from some other Linux would
> do the same job.  I doubt it would match the needs
> of the busybox/isolinux environment.
>
> Our notebooks have 512 MB of RAM on board, and one
> curious feature of udpcast imaging is that the udpcast sender
> is disconnected when there is still about 5 GB of disk
> to be written on the client/receiver.  It continues
> writing from highly compressed zeros in RAM.
>
> I joked with the production manager that if I got shutdown
> to work, they could pack up the notebooks as soon as the
> server disconnected and have them finish writing
> from memory to disk while packed up on the shelf.
> That could save about 5 minutes from the 30 minute job of
> writing a 40 GB drive.

The postinstall script udpreceiver.post is only executed once
udpreceiver has completed, so this can indeed be done.

So, if you just put the following inside, it should work:

#!/bin/sh
sync
sync
echo 5 >/proc/acpi/sleep


The syncs should not even be necessary, as udpreceiver already writes
the file in synchronous mode (O_SYNC flag).


[This is, as long as the echo 5 >/proc/acpi/sleep works. I tried that
on my desktop, but unfortunately it didn't do anything at all. Maybe
on a laptop, it does indeed shut down the machine, or put it to sleep]

> I guess my concern is for any few seconds of timing that
> might be required for the disk cache to finish writing.

O_SYNC mode and the sync commands should take care of that.

> I recall there was a Windows there was a patch to deal
> with allowing for the larger disk cache to do this on
> Windows shutdown.  I don't know if "sleep 5" would do
> the same or it needs 10, 15 or whatever.
>
> --Donald Teed

Or do a sync, followed by the sleep, and another sync to be really
sure.

Alain




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