In order for certain programs to be able to determine where certain partitions are supposed to be mounted by default, the /etc/fstab file is used. A new file /etc/fstab is created containing the following:
cat > /etc/fstab << "EOF"
# Begin /etc/fstab
/dev/<LFS-partition designation> / <fs-type> defaults 1 1
/dev/<swap-partition designation> swap swap defaults 0 0
proc /proc proc defaults 0 0
# End /etc/fstab
<LFS-partition designation>, <swap-partition designation> and <fs-type> have to be replaced with the appropriate values (/dev/hda2, /dev/hda5 and reiserfs for example).