A ZeroDiskInstall, one of ?DebianInstallerIdeas, is an install method requiring USB, CD or DVD drives. The netinst is most of the way there, but seems to require a floppy or CD to kick it off.
Debian can also be installed from another Linux system. See Installation Guide Appendix D.3. Installing Debian GNU/Linux from a Unix/Linux System for instructions: https://www.debian.org/releases/stable/amd64/apds03.en.html
Try the sarge netinst with grub on an old laptop with a broken external floppy, but working linux with a network connection:
rsync me@elsewhere:dnl/sarge-i386-netinst.iso ''boot'' mount /boot/sarge-i386-netinst.iso /mnt/tmp cp -a /mnt/tmp/install /boot/["isolinuxDEB"]
with a grub entry per http://d-i.alioth.debian.org/manual/en.i386/ch05s01.html#boot-initrd :
GRUB grub.conf entry:
title Debian sarge install kernel (hd0,0)/["isolinuxDEB"]/vmlinuz root=/dev/ram devfs=mount,dall initrd (hd0,0)/["isolinuxDEB"]/initrd.gz
Reboot, and then the installer starts up but of course, can't find the cdrom. Try going to a shell to mount the image:
mkdir /mnt mount /dev/disks/disk1/part1 /mnt mount /mnt/sarge-i386-netinst.iso /cdrom -o loop
but sadly, it faults out with:
mount: Could not find a spare loop device
There doesn't seem to be a loopback driver (loop.o) in the netinst config. If /dev/loop* devices were there, perhaps one could manually mount the non-CD and continue the netinstall.
Redhat/Fedora does a ZeroDiskInstall as written in http://www-2.cs.cmu.edu/~colohan/docs/fedora_upgrade.html, but it is not a net install. It requires the CDROM images already downloaded onto the local machine. That method should work for Debian too.
Some people at the original wiki are looking for something similar: http://c2.com/cgi/wiki?NoBootdiskRequired