ubuntu boot # grub-mkconfig -o /boot/grub/grub.cfg
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.9.6-gentoo-r1-kf0
Found initrd image: /boot/initramfs-4.9.6-gentoo-r1-kf0.img
  /run/lvm/lvmetad.socket: connect failed: No such file or directory
  WARNING: Failed to connect to lvmetad. Falling back to internal scanning.
File descriptor 3 (pipe:[2620912]) leaked on vgs invocation. Parent PID 20978: /usr/sbin/grub-probe
  /run/lvm/lvmetad.socket: connect failed: No such file or directory
  WARNING: Failed to connect to lvmetad. Falling back to internal scanning.
  Volume group "main" not found
  Cannot process volume group main
  /run/lvm/lvmetad.socket: connect failed: No such file or directory
  WARNING: Failed to connect to lvmetad. Falling back to internal scanning.
File descriptor 3 (pipe:[2620940]) leaked on vgs invocation. Parent PID 20978: /usr/sbin/grub-probe
  /run/lvm/lvmetad.socket: connect failed: No such file or directory
  WARNING: Failed to connect to lvmetad. Falling back to internal scanning.
  Volume group "main" not found
  Cannot process volume group main
/usr/sbin/grub-probe: error: disk `lvm/vg0-root' not found.
done