If you followed sections 4.3 & 4.4 correctly, you did this:
Code:
cat > ~/.bash_profile << "EOF"
exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash
EOF
Inside the LFS user's home directory. The "\u" means display the user-name at the prompt, so it should look like this:
username:current-directory$ _
That's how you know you're in the lfs account on the host system. The second half (Chapter 6) is tricky because you're running as root inside a chroot. You can make that prompt stand out by adding something like an underscore or a double hash at the beginning of the prompt. Just add it to the chroot options in section 6.4.
Code:
chroot "$LFS" /tools/bin/env -i \
HOME=/root \
TERM="$TERM" \
PS1='##-\u-##:\w\$ ' \
PATH=/bin:/usr/bin:/sbin:/usr/sbin:/tools/bin \
/tools/bin/bash --login +h
Which would make your prompt look like this...
##-username-##:current-directory$ _
And give you an easily visible indication that you're root-within-chroot instead of root at the host, as the latter wouldn't display the hashes.