How to recover grub boot loader on MacBook Air

gistfile1.txt

# Boot from Live CD

root@ubuntu:~# dmesg | grep DMI
[    0.000000] DMI 2.4 present.
[    0.000000] DMI: Apple Inc. MacBookAir1,1/Mac-F42C8CC8, BIOS    MBA11.88Z.00BB.B03.0803171226 03/17/08

root@ubuntu:~# mount --bind /dev /mnt/dev
root@ubuntu:~# mount --bind /sys /mnt/sys
root@ubuntu:~# mount -t proc none /mnt/proc
root@ubuntu:~# chroot /mnt /bin/bash 

root@ubuntu:/# mount -f /
root@ubuntu:/# grub-install /dev/sda
Searching for GRUB installation directory ... found: /boot/grub
Installing GRUB to /dev/sda as (hd0)...
Installation finished. No error reported.
This is the contents of the device map /boot/grub/device.map.
Check if this is correct or not. If any of the lines is incorrect,
fix it and re-run the script `grub-install'.

(hd0)	/dev/sda
root@ubuntu:/# exit

root@ubuntu:~# umount /mnt/sys 
root@ubuntu:~# umount /mnt/proc 
root@ubuntu:~# umount /mnt/dev 
root@ubuntu:~# umount /mnt

ref.
http://www5.big.or.jp/~yamamori/sun/rescue/grub.htm
https://forums.ubuntulinux.jp/viewtopic.php?pid=57491