I am trying to install Debian using Netinstall ISO(Similar to Ubuntu Alternate CD) by booting from GRUB2 of My Lucid Ubuntu already in the System.

I use below menuentry to boot debian-netinst-iso(Which is in /dev/sdb7/debian -directory),by adding these lines to /etc/grub.d/40_custom and "sudo update-grub":
menuentry  "Debian ISO on /dev/sdb7" {
insmod ext2
set root=(hd0,7)
loopback loop /debian/debian-testing-amd64-netinst.iso
linux (loop)/install.amd/vmlinuz boot=install.amd  iso-scan/filename=/debian/debian-testing-amd64-netinst.iso noeject  noprompt 
initrd (loop)/install.amd/initrd.gz
The debian ISO Boots Directly triggering debian-installer-Which asks for where to search for "CD" containing debian-testing-amd64-netinst.iso .This is where the Problem Starts.

I installed Ubuntu Earlier by Symlinking the Ubuntu ISO to CDROM device file /dev/sr0 and install went Fine.
But ,with Debian ISO Booted as Live CD,I cannot Mount Hard Disk Partition(/dev/sdb7) which contains the "debian-testing-netinst-amd64.iso" image.
If I try to Mount ,it Errors Out :
mount:mounting  /dev/sdb7 on /debian failed: No such device

But ,If I search /proc/partitions, I can see hard disk partitions.

the Debian Live CD is operating from tmpfs completely.If I try "df -H" ,It shows tmpfs as mounted.

How Can I mount the hadr disk partitions When the Livecd is booting from tmpfs(ramdisk)?

OR ,Is there a way,I can copy debian-testing-amd64-netinst.iso Which is ~160MB only to RAM ?