Problem when moving New Fstab to the Old Fstab to fix Suse

[cheetahman]

Hello I have problems moving my edited fstab to overwrite the original fstab and i get the error

bash:/dev/null:Permission denied
knoppix:/#

while running the command
su
chroot /mnt/hda7/

I have also made my partition write but I get the errors

Access denied couldn't write to /mnt/hda7/eetc/fstab

Access denined to /mnt/hda7/eetc/fstab