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Re: Skipping fsck during boot with systemd?



Le Tuesday 09 December 2014 16:36:53, The Wanderer a écrit :
> On 12/09/2014 at 10:09 AM, Chris Bannister wrote:
> > On Tue, Dec 09, 2014 at 09:48:58AM +0100, Frédéric Marchal wrote:
> >> Now, is it possible to run fsck during shutdown? Users have been
> >> asking for this for at least 10 years. Is it now acceptable,
> >> possible, tolerated?
> > 
> > That sounds like a recipe for disaster. Do you mean *before*
> > shutdown?
> 
> Obviously, "during shutdown" means "during the shutdown process", i.e.,
> during the sequence of shutting-down-the-system steps which takes place
> in response to a "shutdown" command.
>
> That sequence already does several things prior to actually shutting
> down the system; perhaps most obviously, it tells various "services" to
> stop cleanly, kills other processes, and unmounts filesystems. There
> seems as if there should be no conceptual reason why it shouldn't be
> possible to add an additional "run a fsck" step into that sequence,
> probably after the unmount and before the final shutdown itself.
> 
> ...except that fsck of root during the boot process is possible only
> because root hasn't been mounted yet, because we're still in the
> initramfs and haven't pivoted into the real root yet. So making that
> possible during shutdown would probably require setting up another
> ramdisk during the shutdown process (which sounds like a bad idea),
> pivoting into it, unmounting the original root, and then triggering the
> fsck...

The partition only need to be remounted read only. if I'm understanding it 
correctly.

That's what /etc/init.d/umountroot does during the shutdown sequence. So 
everything is in place to run fsck just before /etc/rc0.d/K10halt.

Now two questions remain:

1) how to invoke an additional hypothetical /etc/rc0.d/K10fsck on demand?

2) is it wise to run fsck at that time? I have seen strong opposition in the 
past. Mostly turning around the risk that the user would switch the power off 
or the power supply would fail resulting in a damaged partition. As the risk 
seems as high during the boot sequence, I don't understand the opposition.


> All in all, while it *might* be possible, I don't think it sounds like
> that would be worth the trouble.

That's probably right too...

Frederic


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