Red Hat Enterprise Linux 4 rescue mode using the HTTP and NFS method, gives two different rescue environments

Issue

• Booting into RHEL 4.7 rescue mode using the HTTP and NFS method, gives two different rescue environments :

  default RHEL4.7-i386-ES
  label   RHEL4.7-i386-ES
      kernel RHEL4.7-i386-ES/vmlinuz
      append rescue initrd=RHEL4.7-i386-ES/initrd.img ramdisk_size=10000 text nofb
  

1. Using NFS : a bash shell and all commands are available, such as scp, ssh, ftp (even if you skip mounting the existing installation)

-/bin/sh-3.00# which scp
/usr/bin/scp

2. Using Http : a bourne shell and scp,ssh are only available if the existing installation is mounted.

#which scp
/mnt/sysimage/usr/bin/scp

• Why is this difference present between http and nfs?