Debian – kernel update – WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!

debiankernellvm

I just updated one of our debian jessie servers and the kernel was updated, nothing special, as we have done this many times. But the first time there were some warnings when the grub configuration file was being generated. I have never seen them before. As far as I can tell the system runs nicely after a reboot.

Setting up linux-image-3.16.0-4-amd64 (3.16.7-ckt25-2+deb8u3) ...
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-3.16.0-4-amd64
/etc/kernel/postinst.d/zz-update-grub:
Generating grub configuration file ...
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
Found linux image: /boot/vmlinuz-3.16.0-4-amd64
Found initrd image: /boot/initrd.img-3.16.0-4-amd64
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
  WARNING: lvmetad is running but disabled. Restart lvmetad before enabling it!
done

I searched for the warning online, but I couldn't find a decent explanation that made sense to me (maybe not understood?) and also couldn't understand if this can be ignored. Anyone here has an idea? Thanks

Best Answer

according to info from Peter Rajnoha about an old 2014 fedora bug 1152185, "The warning is there because if lvmetad is already instantiated and running, then using use_lvmetad=0 will cause LVM commands run under this setting to not notify lvmetad about any changes - therefore lvmetad may miss some information - hence the warning.".

https://bugzilla.redhat.com/show_bug.cgi?id=1152185

However, in our case use_lvmetad = 0, so I tend to believe the warnings appear only during the update and the grub reconfiguration.

According to the explanations in the bug report, this is connected with lvm2-monitor, which is happily running on my system, I believe on yours too. Please check out the Process line:

# systemctl status lvm2-monitor
รข lvm2-monitor.service - Monitoring of LVM2 mirrors, snapshots etc. using     dmeventd or progress polling
   Loaded: loaded (/lib/systemd/system/lvm2-monitor.service; enabled)
   Active: active (exited) since Sat 2016-07-09 04:04:49 EEST; 34min ago
     Docs: man:dmeventd(8)
           man:lvcreate(8)
           man:lvchange(8)
           man:vgchange(8)
  Process: 328 ExecStart=/sbin/lvm vgchange --monitor y --ignoreskippedcluster (code=exited, status=0/SUCCESS)
 Main PID: 328 (code=exited, status=0/SUCCESS)
   CGroup: /system.slice/lvm2-monitor.service

I do not see any traces of the warning after reboot and based on the other information I believe the warning is safe to ignore at this stage. If you get any more or other warnings, you should look into it further.

Also, I used to receive LVM warnings on each image update or grub reconfiguration about the names I believe, which turned out to be unimportant and most probably connected to the old hardware. So this is not uncommon.

Preexo, I hope that this has answered your two concerns. Rubo77, I hope I have been helpful for you too.

Kind regards!

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