No medium found error on update-grub

Question

root@ano:~# update-grub
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
Found linux image: /boot/vmlinuz-5.4.0-148-generic
Found initrd image: /boot/initrd.img-5.4.0-148-generic
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
  /dev/sda: open failed: No medium found
done