Then you forgot one or more steps leading up to this error. If you have to change any of the commands that are in the book to make things work then something is wrong and you should fix the problem before continuing.
Without knowing what you did and didn't do, I would suggest revisiting all the previous chapters to find out which mistake was made.
An educated guess would be the chown commands in 4.3. Adding the LFS User
. If that is the case, you need to start over from 4.3 and remove all you already did from chapter 5.