Bug#719738: [PATCH] Please install the lvm2 systemd generator

[Michael Stapelberg]

Hi Bastian,

Bastian Blank <waldi at debian.org> writes:
> On Thu, Aug 15, 2013 at 10:24:42AM +0200, Michael Stapelberg wrote:
>> Bastian Blank <waldi at debian.org> writes:
>> > The init-script calls vgchange -ay. Why does this not work?
>> Because the init script is called only once during boot, whereas new
>> devices may also appear later. As an example, in the case that Vincent
>> Bernat brought up, the lvm2 init script runs after the first hard disk
>> is crypto-unlocked and available, but does not run again (obviously)
>> after the second hard disk becomes crypto-unlocked (with a key file that
>> is stored on the first one).
>
> The lvm2 init-script declares a lazy dependency on the udev init-script,
> which is unquestionable available. The later makes sure the hardware is
> available by waiting.
>
> The description tells me:
> | # Short-Description: Start udevd, populate /dev and load drivers.
> If this is not longer true, fix this first.

The systemd service file for udev, which we take directly from upstream,
does not wait on all the hardware arriving before continuing. Instead,
upstream’s view (specifically Kay’s view as the udev maintainer) is that
Linux is event-driven and udev handles these events whenever they occur,
not in a “let’s wait for all hardware and just ignore anything that
comes up later” fashion :-). We don’t want to diverge from upstream in
that key point of how udev works.

Therefore, I ask you again to please include the patch I attached to
this bugreport in order to make lvm work much better on a Debian machine
using systemd.

I don’t quite understand why you are hesitant to do that, given that
there are absolutely no changes to sysvinit users. Maybe you can clarify
what your concern is, if any?

Thanks.

-- 
Best regards,
Michael