Installing Debian can be achieved by using booting your box from the network. This is how I set up my server to allow clients to boot from it.
PXE Configuration
This needs to be added to your /tftproot/pxelinux.cfg/default file. Refer to PXE-Linux-Boot-Server on how to set up a PXE server.
label debianbuster-min-vm
MENU LABEL ^Debian Autoinstall Buster Minimal VM
LINUX /debian/buster/debian-installer/amd64/linux
INITRD /debian/buster/debian-installer/amd64/initrd.gz
APPEND vga=788 preseed/url=tftp://server/debian/preseed-buster-min-vm.txt debian-installer/locale=en_US debian-installer/country=US debian-installer/language=en debian-installer/allow_unauthenticated_ssl=true keyboard-configuration/xkb-keymap=us netcfg/get_hostname=debian netcfg/get_domain=local.domain --- quiet
TEXT HELP
User:root
Pass:root
ENDTEXT
label debianbuster-desktop
MENU LABEL ^Debian Autoinstall Buster Desktop
LINUX /debian/buster/debian-installer/amd64/linux
INITRD /debian/buster/debian-installer/amd64/initrd.gz
APPEND vga=788 preseed/url=tftp://server/debian/preseed-buster-desktop.txt debian-installer/locale=en_US debian-installer/country=US debian-installer/language=en debian-installer/allow_unauthenticated_ssl=true keyboard-configuration/xkb-keymap=us netcfg/get_hostname=debian netcfg/get_domain=local.domain --- quiet
TEXT HELP
User:root
Pass:root
ENDTEXT
TFTP
A directory needs to be created as referenced above with the PXE configuration and the netboot files will also need to be downloaded and extracted into it.
mkdir -p /tftproot/debian/buster
cd /tftproot/debian/buster
wget http://ftp.debian.org/debian/dists/buster/main/installer-amd64/current/images/netboot/netboot.tar.gz
tar zxf netboot.tar.gz
Preseed
A Debian preseed file allows you to answer the installer prompts automatically. It is very useful for unattended/automatic installs. I have created one for a desktop and one for a minimal virtual Machine. They should be placed in the /tftproot/debian directory and are referenced by the PXE configuration above in the APPEND lines, so make sure they are named appropriately.