initramfs - need to edit text file

I'm stuck in initramfs on Linux Mint v15 and I need to edit /bin/grub/grub/cfg. I have the sda1 device mounted but not sure what to do to edit. I try exec ./usr/bin/vi and it throws a kernel panic.

Now there are options to do. I followed the below path:

1. Make a temp directory.

2. Mount the root filesystem (/) on the temp directory.

3. Then chroot it.

   (initramfs) mkdir /mnt

   (initramfs) mount /dev/device-name /mnt

   (initramfs) chroot /mnt

   $ vi