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Old 04-02-2008, 03:50 PM
Steven Lembark
 
Default Emergency shutdown, how to?

Liviu Andronic wrote:
> On Fri, Mar 28, 2008 at 10:07 AM, Dale <dalek1967@bellsouth.net> wrote:
>>> By the way the safest and recommended command, although a bit longish
>>> should be ALT+SysRq(or print)+S(ync)+U(mount)+B(Reboot).
>>>
>> Since I wanted to shutdown instead of reboot, it would be ALT + SysRq + S +
>> U + O then correct?
>
> Are there any potential harms to the hardware / system in case one
> tends to abuse (i.e. use more often than necessary) of this command?
> It's so often so tempting to shut down your system fast.

Short of a serious emergency (e.g., UPS with
30-sec lag and no input power) stick with
'shutdown -fh now'. The main problem is that
you bypass the stop phase of all the app's
started up via init.d; very little short of
just hitting the reset switch or yanking the
power.

--
Steven Lembark +1 888 359 3508
Workhorse Computing 85-09 90th St
lembark@wrkhors.com Woodhaven, NY 11421
--
gentoo-user@lists.gentoo.org mailing list
 
Old 04-02-2008, 05:28 PM
Volker Armin Hemmann
 
Default Emergency shutdown, how to?

On Mittwoch, 2. April 2008, Steven Lembark wrote:
> Liviu Andronic wrote:
> > On Fri, Mar 28, 2008 at 10:07 AM, Dale <dalek1967@bellsouth.net> wrote:
> >>> By the way the safest and recommended command, although a bit longish
> >>> should be ALT+SysRq(or print)+S(ync)+U(mount)+B(Reboot).
> >>
> >> Since I wanted to shutdown instead of reboot, it would be ALT + SysRq
> >> + S + U + O then correct?
> >
> > Are there any potential harms to the hardware / system in case one
> > tends to abuse (i.e. use more often than necessary) of this command?
> > It's so often so tempting to shut down your system fast.
>
> Short of a serious emergency (e.g., UPS with
> 30-sec lag and no input power) stick with
> 'shutdown -fh now'. The main problem is that
> you bypass the stop phase of all the app's
> started up via init.d; very little short of
> just hitting the reset switch or yanking the
> power.

if you do it the right way, start with 'e' and 'i', all apps are cleanly
terminated/killed. So if an app does not quit cleanly, it is broken.

The correct sequence is: e,i,u,b/o and it is absolutly save.
--
gentoo-user@lists.gentoo.org mailing list
 
Old 04-02-2008, 05:40 PM
Michael Schmarck
 
Default Emergency shutdown, how to?

Dirk Heinrichs <dirk.heinrichs.ext@nsn.com>:

> Am Mittwoch, 2. April 2008 schrieb ext Michael Schmarck:
>> Dirk Heinrichs <dirk.heinrichs.ext@nsn.com> wrote:
>> > Am Mittwoch, 2. April 2008 schrieb ext Michael Schmarck:
>> >> You're not shutting down the system in a clean way.
>> >
>> > You're not? I thought that's the purpose of the whole thing?
>>
>> It's more like pulling the plug, isn't it? At least none of
>> the shutdown scripts is run. And if you don't run ALT + SysRq + U,
>> or if it just doesn't work (like hangs at some (remote) fs),
>
> But nobody proposed _not_ to run ALT + SysRq + U,

True, but if things come to worse, you've got to do a ALT+SysRq+B
or +O, even before +U completely returned. As said, it can happen,
that U(nmount) doesn't work - and then you'd need to shutdown
anyway.

> Neil even proposed ALT +
> SysRq + EISUB, to be sure everything is killed, sync'd and unmounted.

Which might or might not work. But note that I was also talking
about applications being in a corrupted state (the database example).

>> filesystems aren't even unmounted and thus dirty and thus need
>> a fsck run on next boot.
>
> XFS to the rescue :-)

Yep. Well, to be honest, I haven't had a fs die on me, because
of a Alt+SysRq+B.

Michael Schmarck
--
Inspiration without perspiration is usually sterile.


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Old 04-02-2008, 05:48 PM
Neil Bothwick
 
Default Emergency shutdown, how to?

On Wed, 02 Apr 2008 19:40:37 +0200, Michael Schmarck wrote:

> > Neil even proposed ALT +
> > SysRq + EISUB, to be sure everything is killed, sync'd and
> > unmounted.
>
> Which might or might not work. But note that I was also talking
> about applications being in a corrupted state (the database example).

E sends a SIGTERM to all applications. Any well behaved application
should shut down cleanly on this. I sends a SIGKILL, but it only affects
programs that were so locked up they ignored E, so you have nothing to
lose by then.


--
Neil Bothwick

Weird enough for government work.
 

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