# sudo grub-probe -d /dev/sda2 --verbose
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: /dev/sda2 starts from 546210
grub-probe: info: opening the device hd0
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: DOS partition 0 starts from 63
grub-probe: info: DOS partition 1 starts from 546210
grub-probe: info: opening hd0,2
grub-probe: info: the size of hd0 is 625142448
grub-probe: error: unknown filesystem
Might also be useful:
# sudo grub-probe -d /dev/sda2 --verbose
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: the size of hd1 is 7936000
grub-probe: info: /dev/sda2 starts from 546210
grub-probe: info: opening the device hd0
grub-probe: info: the size of hd0 is 625142448
grub-probe: info: DOS partition 0 starts from 63
grub-probe: info: DOS partition 1 starts from 546210
grub-probe: info: opening hd0,2
grub-probe: info: the size of hd0 is 625142448
grub-probe: error: unknown filesystem