grub

hey every body , i just installed ubuntu alongside of arch and that make arch boot partition be removed( i think by my bad installation) . so now i want to get back my arch . i formated the boot partition (on /dev/sda1) and with a bootable arch in usb-flash i did :

mksfs.ext4 /dev/sda1mount /dev/sda3 /mntarch-chroot /mnt mount /dev/sda1 /bootgrub-install /dev/sda1

but it give this error :`warning  : file system ext2 dosnot support embedingwarning : grub can only be installed in this setup by using block lists.error : will not proceed with blocklist`my partiions :`number   start     end size type file system flags1              1049kB 368MB  primary ext4    boot2              368MB  4562MB primary linux-swap3              4562     74.6G     primary ext44              ...5               ....6              ....`where is the problem , i just installed arch by this partitioning before , why now it give this error   ??