Bug#791869: System hangs on boot with lvmetad not active

[Ben Caradoc-Davies]

This bug now makes any kernel upgrade (in this case 
linux-image-4.0.0-2-amd64) cause the system to be unbootable. The system 
is unable to contact lvmetad and unable to locate the root partition. 
There is no luks passphrase prompt.

Please upgrade this bug to CRITICAL. Or should I file a critical bug 
against all kernels? Or do users get what is coming to them for 
upgrading to a package with an open grave bug?

Stefan, your systemd.unit=emergency.service vgchange instructions do not 
work, even with vgchange -ay --config 'global{use_lvmetad=0}' as 
suggested here:
https://bugzilla.redhat.com/show_bug.cgi?id=813766

cryptsetup is not available so I do not know how this would work anyway.

Workaround is to:
- Boot another kernel+initramfs (e.g. linux-image-4.0.0-1-amd64)
- Disable lvmetad by editing /etc/lvm/lvm.conf to set "use_lvmetad = 0"
- Run update-initramfs -u
- Reboot into linux-image-4.0.0-2-amd64

Once this is done I can boot. I see:

root at ripley:~# pvs
   PV                     VG   Fmt  Attr PSize  PFree
   /dev/mapper/sda2_crypt vg   lvm2 a--  55.62g    0
root at ripley:~# vgs
   VG   #PV #LV #SN Attr   VSize  VFree
   vg     1   2   0 wz--n- 55.62g    0
root at ripley:~# lvs
   LV   VG   Attr       LSize  Pool Origin Data%  Meta%  Move Log 
Cpy%Sync Convert
   home vg   -wi-ao---- 36.99g 

   root vg   -wi-ao---- 18.62g 


Kind regards,

-- 
Ben Caradoc-Davies <ben at transient.nz>
Director
Transient Software Limited <http://transient.nz/>
New Zealand