Comment 13 for bug 1416396

This isn't a grub2 bug, but an issue caused by the way os-prober does the filesystem probing to display other installs in the grub menu. I'm setting both the grub2 and os-prober tasks to "Won't Fix": if we really want to make these messages disappear, the changes will not happen in os-prober or grub2.

The ideal solution to this is to deactivate os-prober on the system; otherwise a lot of effort may be needed to reduce the severity of the messages (although they are relevant, and certainly meaningful, if someone goes to mount a filesystem with the wrong type). To figure out whether another install exists on the disks, os-prober needs to do some probing and mounting of the filesystems (we can't use only the partition table to guess the filesystem) to see if there are kernels, or configuration files, it understands and to read them to know what the other operating system is.

My recommendation is to set GRUB_DISABLE_OS_PROBER=true in /etc/default/grub to disable probing if no other operating systems are installed on this system; then no probing will happen on upgrades, so no messages will show up on the console.