Upgraded to 16.04 and now getting error message

Solution 1:

This is an inofensive message and you should not worry about it.

If you do 'man lvmetad' you'll find that it is a daemon that caches disk metadata. If this daemon is not available, lvm will read the metadata from the disk. This may be a problem with very complex systems with hundreds of volumes, but it is not for a desktop.

Every message that says it has been solved by touching grub or after installing some packages, has probably solved by upgrading the system and recreating the grub configuration.

This is a very very low priority bug and was there in Ubuntu and Debian for a while. Probably will dissapear in a upgrade without doing anything.

I've got that message for a while and without any adverse condition.

People complaining to be unable to login are being affected by another error and should continue checking the logs to find it.