sorry am bit poor in these things , but

"cp -r /lib/modules/* /mnt/ubuntu/lib/modules/
cp /lib/firmware/* /mnt/ubuntu/lib/firmware/
chroot /mnt/ubuntu /bin/bash
useradd -m <replace with your username here> (e.g useradd -m mohammad)
# fill in details as you wish.
visudo
# Edit the file and add your username to sudoers using visudo
# Example (replace my username with yours)
# # User privilege specification
# root ALL=(ALL) ALL
# mohammad ALL=(ALL) ALL"

do we need to enter all these above codes on N900