grub boot error : “symbol ‘grub_calloc’ not found

After updating grub2 and rebooting, my server does not boot:

Booting from Hard Disk 0...
error: symbol `grub_calloc' not found.
Entering rescue mode...
grub rescue> _

Solution:
You have to detach you /dev/sda1 volume from the ec2 instance.
Mount it on another server (probably start a new temp rescue server with the same operating system)
Login in to the rescue server and

$ sudo su -
# mkdir /rescue
# mount /dev/sdc1 /rescue
# for fs in {proc,sys,tmp,dev}; do mount -o bind /$fs /rescue/$fs; done
# cd /rescue
# chroot /rescue
# lsblk <-- this will identify the attached disk, usualy /dev/sdc
# grub-install /dev/sdc
# exit
# cd /
# for fs in {proc,sys,tmp,dev}; do umount /rescue/$fs; done
# umount /rescue

detach fixed volume from rescue server
attach it back to the original server (as /dev/sda1)
done