Chroot Ubuntu from Live CD

sudo mount /dev/sdXY /mnt
sudo mount --bind /dev /mnt/dev \
    && sudo mount --bind /dev/pts /mnt/dev/pts \
    && sudo mount --bind /proc /mnt/proc \
    && sudo mount --bind /sys /mnt/sys

sudo chroot /mnt

exit \
    && sudo umount /mnt/sys \
    && sudo umount /mnt/proc \
    && sudo umount /mnt/dev/pts \
    && sudo umount /mnt/dev \
    && sudo umount /mnt

Source