Bug#774082: systemd: system with LVM and lvmetad does not bot after upgrade to jessie

[Michael Biebl]

On Fri, 02 Jan 2015 12:13:06 +0100 Peter Rajnoha <prajnoha at redhat.com>
wrote:
> The way the LV with root FS is activated depends on distribution,
> but most of the time, this LV is not activated automatically as
> lvmetad is not running in initramfs. Therefore, it's a matter of
> initramfs script to activate the LV with root FS directly with
> direct vgchange/lvchange -aay call.
> 
> For the rest of the LVs (where non-root filesystems reside), we
> can rely on lvmetad and the udev rule to activate these LVs
> (it's the "pvscan --cache -aay" call in udev rule that does
> the actual activation based on information cached in lvmetad -
> if all the PVs making up the VG are present, the VG is activated).
> 
> Also, care must be taken that lvmetad socket unit (lvm2-lvmetad.socket)
> is always enabled so whenever the use_lvmetad=1 is used in lvm.conf,
> the lvm2-lvmetad.service is automatically started based on that
> socket unit.
> 
> As for the messages about LVM scanning in initramfs - LVM does a
> fallback to direct scanning instead of reading this info from
> lvmetad if lvmtead is not yet running and at the same time use_lvmetad=1
> is used - it means nobody started lvmetad daemon in lvmetad.
> So either initramfs needs to include lvmetad (and make sure it's
> started) OR initramfs needs modified lvm.conf which always has
> use_lvmetad=0 (normally, when generating initramfs image, the lvm.conf
> needs to be modified a bit so it's suitable for initramfs environment).
> 
> So this just seems that the initramfs scripts and systemd units
> are not set up properly - this needs to be inspected:
> 
>   1) is lvm2-lvmetad.socket systemd unit enabled?

By default this is the case.

>   2) is lvmetad supposed to be used in initramfs at all?

Debian uses initramfs-tools by default.
The lvm2 hooks for initramfs-tools do not use lvmetad.

>     2a) if yes, is systemd used in initramfs

initramfs-tools does not use systemd.

>       2aa) if yes, is lvm2-lvmetad.socket unit present and enabled there?
>           (as well as lvm2-lvmetad.service unit and lvmetad binary present in initramfs)
>       2ab) if no, is lvmetad started directly within initramfs script?
>     2b) if no, is there a direct vgchange/lvchange -aay call in initramfs script?
>         (also, is lvm.conf modified for initramfs script so that use_lvmetad=0 is used
>          for the "fallback to direct LVM scan" warning messages to disappear)
> 
> And whenever lvmetad is used - either in initramfs in the system itself,
> there must always be the udev rule with "pvscan --cache -aay" call present.
> 
> So these are the items to check (..by Debian maintainers of respective parts).

Vincent, looks like you weren't CCed, so you didn't get the message.

Peter, if the initramfs does *not* use lvmetad (as is the case with the
default initramfs-tools setup), does it actually work if the root file
system uses lvm in lvmetad = 1 mode?
-- 
Why is it that all of the instruments seeking intelligent life in the
universe are pointed away from Earth?

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