Re: Runlevel for Sleep?

["P. Christeas" <p_christ-U04EIuiosng@public.gmane.org>]

Pavel Machek wrote:
> Hi!
>
> > connections. What happens if you are suspending a db server (well,
> > suspending a server is IMHO a really stupid thing, but...) and after
>
> Why?
>
Those are useful questions to ask. Scripts are flexible enough to handle 
special cases, we however have to ensure there are no stiff restrictions to 
those.

> You bought new UPS for your server. How do you install it without
> bringing machine down? Suspend to disk, rearrange power cables,
> resume.
>
> You have your server on UPS. Power died, and UPS is indicating 30
> seconds to failure. What do you do? Suspend to disk.
>
AFAIK there is already a 'low battery' line in 'inittab'. Following from that 
point, we should use that line (for ACPI) instead of directly (from a binary) 
trying to enter S4 or whatever. This way the root will chose how to handle 
such a situation. In some machines S4 may be broken (not ACPI's fault always, 
consider a mis-configured partition), there 'init 0' is the only safe way to 
go down (see S5). Only the root of the machine may know that.
This will certainly be a consideration point if we decide to implement (as a 
de-facto standard) the runlevel.

> Ethernet card in your server died. You want to replace it. Your
> server is not hotplug capable. What do you do? Suspend to disk,
> replace ethernet card, resume. If you are fast your users will not
> even see broken connections.
>
Q. Will that really work?  Won't the change of Ethernet MAC ruin that?
Anyway, everybody should be free to try that.

> [I've created FAQ section in Documentation/swsusp.txt; I'll put this
> question/answer in there in next merge.]
> 								Pavel



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