event based initramfs

[Steve Langasek]

On Fri, May 11, 2012 at 10:25:48AM -0400, Phillip Susi wrote:
> On 5/11/2012 4:04 AM, Robert Collins wrote:
> >So a related issue is dmraid, which is very similar to mdadm. My last
> >two dmraid machines fail - every time - to activate on boot. The
> >reason being that the devices they depend upon don't come up fast
> >enough, and the configuration process isn't event-driven *enough* to

> Event driven *enough*?  What do you mean?  How can it be more or
> less event driven ( in other words, either it is or is not, there
> isn't really an in between )?  When the drive add event comes in,
> udev runs dmraid to activate the array.  As long as that happens
> before wait-for-root gives up, all is well.

> If you're getting timeouts, then either the timeout is too short, or
> you have some VERY slow initializing hardware.  How would upstart
> help this?

Strawman (not something we discussed in the UDS session):

 - mountall runs as a job that waits indefinitely for the root filesystem
 - failsafe-recover is a job that sets a timeout; if the timeout is hit,
   it *deactivates* (but does not kill) plymouth and spawns a recovery
   shell.
 - if the device eventually arrives after the shell has been started,
   mountall emits an "I'm done" event that stops the shell job, restarts the
   plymouth splash, and pivots root.

This would be a useful usability improvement over what we have now.

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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