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Re: Not stopping daemons, where are we?

On Wed, Jul 2, 2008 at 8:30 PM, Marvin Renich <mrvn@renich.org> wrote:
> * Bernd Eckenfels <ecki@lina.inka.de> [080701 20:45]:
>> In article <[🔎] 20080701223517.GB2670@dario.dodds.net> you wrote:
>> >> I mean the pending-write case is the most obvious. But what about resolver
>> >> caches, VPNs and the like?
>> >
>> > What kind of data loss do you expect to arise from shutting down a VPN
>> > client without giving it time to save state?
>> I dont expect any data loss - hopefully protocols are not that
>> optimistic/broken. But with unclean shutdown you can affect external parties
>> with unexected errors. Like resolver problems, user not found and similiar
>> problems.
> Either I don't understand the usage scenario you are talking about, or I
> misunderstand what is being proposed in this thread, or you
> misunderstand what is being proposed in this thread.  Here is a more
> concrete example of a situation based on what I think is being proposed:
> The Debian maintainer for a specific VPN decides it does not need
> special shutdown handling, so he marks it to not require calling
> "/etc/init.d/SuperVPN stop" when doing a shutdown or reboot.  This is
> what I understand this thread is about.  This will result in SuperVPN
> not being stopped until the final "kill all remaining processes" step of
> the halt or reboot (i.e. don't waste time shutting this daemon down
> cleanly, let it die abruptly just before halting).
> Now, some other unrelated app, possibly a Debian-provided package and
> possibly one installed manually by the sysadmin, uses this VPN and needs
> it to be running during the app's normal shutdown (done using the
> traditional /etc/init.d/* script) to avoid data loss.  The sysadmin or
> Debian maintainer will know that a clean shutdown is required, so will
> not mark this init script as "skippable" during the normal shutdown
> sequence.
> When the system shuts down, since this other app is not explicitly
> marked as "safe to kill without init script during system shutdown", its
> init script gets called as usual during shutdown.  At this point, the
> VPN is still up, because the "kill all processes" only happens _after_
> all init scripts have been called for running daemons.
> What is the problem you think might occur with the proposal from this
> thread?
We can add even more flexibility: You may leave today's scripts as they are, and
add "skippable" flag somewhere around LSB headers or /etc/default/<name>.
Then if system administrator will have some weired situation where he
should like
to perform explicit shutdown for particular service - it can just
unset "skippable" flag
for that service.

This will also ease transition - if some service is not explicitly
marked as "skippable", then its
not skippable, i.e. you surely do not harm init scripts that are not
up to date yet.

> ...Marvin
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