The installer may be booted using boot files placed on an existing hard drive partition, either launched from another operating system or by invoking a boot loader directly from the BIOS. On modern UEFI systems, the kernel may be booted directly from the UEFI partition without the need of a boot loader.
A full, “pure network” installation can be achieved using this technique. This avoids all hassles of removable media, like finding and burning CD/DVD images.
This section explains how to add to or even replace an existing linux installation using GRUB.
At boot time, GRUB supports loading in memory not only the kernel, but also a disk image. This RAM disk can be used as the root file-system by the kernel.
Copy the following files from the Debian archives to a
convenient location on your hard drive, for instance to
vmlinuz (kernel binary)
initrd.gz (ramdisk image)
If you intend to use the hard drive only for booting and then download everything over the network, you should download the netboot/debian-installer/amd64/initrd.gz file and its corresponding kernel netboot/debian-installer/amd64/linux. This will allow you to repartition the hard disk from which you boot the installer, although you should do so with care.
Alternatively, if you intend to keep an existing partition on the hard
drive unchanged during the install, you can download the
hd-media/initrd.gz file and its kernel
hd-media/vmlinuz, as well as
copy an installation image to the hard drive (make sure the file is named ending in
.iso). The installer can then boot from the hard drive
and install from the installation image, without needing the network.
Finally, to configure the bootloader proceed to Section 5.1.3, “Booting from Linux using GRUB”.